| 1 | /* |
| 2 | * linux/fs/namei.c |
| 3 | * |
| 4 | * Copyright (C) 1991, 1992 Linus Torvalds |
| 5 | */ |
| 6 | |
| 7 | /* |
| 8 | * Some corrections by tytso. |
| 9 | */ |
| 10 | |
| 11 | /* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname |
| 12 | * lookup logic. |
| 13 | */ |
| 14 | /* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture. |
| 15 | */ |
| 16 | |
| 17 | #include <linux/init.h> |
| 18 | #include <linux/export.h> |
| 19 | #include <linux/kernel.h> |
| 20 | #include <linux/slab.h> |
| 21 | #include <linux/fs.h> |
| 22 | #include <linux/namei.h> |
| 23 | #include <linux/pagemap.h> |
| 24 | #include <linux/fsnotify.h> |
| 25 | #include <linux/personality.h> |
| 26 | #include <linux/security.h> |
| 27 | #include <linux/ima.h> |
| 28 | #include <linux/syscalls.h> |
| 29 | #include <linux/mount.h> |
| 30 | #include <linux/audit.h> |
| 31 | #include <linux/capability.h> |
| 32 | #include <linux/file.h> |
| 33 | #include <linux/fcntl.h> |
| 34 | #include <linux/device_cgroup.h> |
| 35 | #include <linux/fs_struct.h> |
| 36 | #include <linux/posix_acl.h> |
| 37 | #include <linux/hash.h> |
| 38 | #include <asm/uaccess.h> |
| 39 | |
| 40 | #include "internal.h" |
| 41 | #include "mount.h" |
| 42 | |
| 43 | /* [Feb-1997 T. Schoebel-Theuer] |
| 44 | * Fundamental changes in the pathname lookup mechanisms (namei) |
| 45 | * were necessary because of omirr. The reason is that omirr needs |
| 46 | * to know the _real_ pathname, not the user-supplied one, in case |
| 47 | * of symlinks (and also when transname replacements occur). |
| 48 | * |
| 49 | * The new code replaces the old recursive symlink resolution with |
| 50 | * an iterative one (in case of non-nested symlink chains). It does |
| 51 | * this with calls to <fs>_follow_link(). |
| 52 | * As a side effect, dir_namei(), _namei() and follow_link() are now |
| 53 | * replaced with a single function lookup_dentry() that can handle all |
| 54 | * the special cases of the former code. |
| 55 | * |
| 56 | * With the new dcache, the pathname is stored at each inode, at least as |
| 57 | * long as the refcount of the inode is positive. As a side effect, the |
| 58 | * size of the dcache depends on the inode cache and thus is dynamic. |
| 59 | * |
| 60 | * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink |
| 61 | * resolution to correspond with current state of the code. |
| 62 | * |
| 63 | * Note that the symlink resolution is not *completely* iterative. |
| 64 | * There is still a significant amount of tail- and mid- recursion in |
| 65 | * the algorithm. Also, note that <fs>_readlink() is not used in |
| 66 | * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink() |
| 67 | * may return different results than <fs>_follow_link(). Many virtual |
| 68 | * filesystems (including /proc) exhibit this behavior. |
| 69 | */ |
| 70 | |
| 71 | /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation: |
| 72 | * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL |
| 73 | * and the name already exists in form of a symlink, try to create the new |
| 74 | * name indicated by the symlink. The old code always complained that the |
| 75 | * name already exists, due to not following the symlink even if its target |
| 76 | * is nonexistent. The new semantics affects also mknod() and link() when |
| 77 | * the name is a symlink pointing to a non-existent name. |
| 78 | * |
| 79 | * I don't know which semantics is the right one, since I have no access |
| 80 | * to standards. But I found by trial that HP-UX 9.0 has the full "new" |
| 81 | * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the |
| 82 | * "old" one. Personally, I think the new semantics is much more logical. |
| 83 | * Note that "ln old new" where "new" is a symlink pointing to a non-existing |
| 84 | * file does succeed in both HP-UX and SunOs, but not in Solaris |
| 85 | * and in the old Linux semantics. |
| 86 | */ |
| 87 | |
| 88 | /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink |
| 89 | * semantics. See the comments in "open_namei" and "do_link" below. |
| 90 | * |
| 91 | * [10-Sep-98 Alan Modra] Another symlink change. |
| 92 | */ |
| 93 | |
| 94 | /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks: |
| 95 | * inside the path - always follow. |
| 96 | * in the last component in creation/removal/renaming - never follow. |
| 97 | * if LOOKUP_FOLLOW passed - follow. |
| 98 | * if the pathname has trailing slashes - follow. |
| 99 | * otherwise - don't follow. |
| 100 | * (applied in that order). |
| 101 | * |
| 102 | * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT |
| 103 | * restored for 2.4. This is the last surviving part of old 4.2BSD bug. |
| 104 | * During the 2.4 we need to fix the userland stuff depending on it - |
| 105 | * hopefully we will be able to get rid of that wart in 2.5. So far only |
| 106 | * XEmacs seems to be relying on it... |
| 107 | */ |
| 108 | /* |
| 109 | * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland) |
| 110 | * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives |
| 111 | * any extra contention... |
| 112 | */ |
| 113 | |
| 114 | /* In order to reduce some races, while at the same time doing additional |
| 115 | * checking and hopefully speeding things up, we copy filenames to the |
| 116 | * kernel data space before using them.. |
| 117 | * |
| 118 | * POSIX.1 2.4: an empty pathname is invalid (ENOENT). |
| 119 | * PATH_MAX includes the nul terminator --RR. |
| 120 | */ |
| 121 | void final_putname(struct filename *name) |
| 122 | { |
| 123 | if (name->separate) { |
| 124 | __putname(name->name); |
| 125 | kfree(name); |
| 126 | } else { |
| 127 | __putname(name); |
| 128 | } |
| 129 | } |
| 130 | |
| 131 | #define EMBEDDED_NAME_MAX (PATH_MAX - sizeof(struct filename)) |
| 132 | |
| 133 | struct filename * |
| 134 | getname_flags(const char __user *filename, int flags, int *empty) |
| 135 | { |
| 136 | struct filename *result, *err; |
| 137 | int len; |
| 138 | long max; |
| 139 | char *kname; |
| 140 | |
| 141 | result = audit_reusename(filename); |
| 142 | if (result) |
| 143 | return result; |
| 144 | |
| 145 | result = __getname(); |
| 146 | if (unlikely(!result)) |
| 147 | return ERR_PTR(-ENOMEM); |
| 148 | |
| 149 | /* |
| 150 | * First, try to embed the struct filename inside the names_cache |
| 151 | * allocation |
| 152 | */ |
| 153 | kname = (char *)result + sizeof(*result); |
| 154 | result->name = kname; |
| 155 | result->separate = false; |
| 156 | max = EMBEDDED_NAME_MAX; |
| 157 | |
| 158 | recopy: |
| 159 | len = strncpy_from_user(kname, filename, max); |
| 160 | if (unlikely(len < 0)) { |
| 161 | err = ERR_PTR(len); |
| 162 | goto error; |
| 163 | } |
| 164 | |
| 165 | /* |
| 166 | * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a |
| 167 | * separate struct filename so we can dedicate the entire |
| 168 | * names_cache allocation for the pathname, and re-do the copy from |
| 169 | * userland. |
| 170 | */ |
| 171 | if (len == EMBEDDED_NAME_MAX && max == EMBEDDED_NAME_MAX) { |
| 172 | kname = (char *)result; |
| 173 | |
| 174 | result = kzalloc(sizeof(*result), GFP_KERNEL); |
| 175 | if (!result) { |
| 176 | err = ERR_PTR(-ENOMEM); |
| 177 | result = (struct filename *)kname; |
| 178 | goto error; |
| 179 | } |
| 180 | result->name = kname; |
| 181 | result->separate = true; |
| 182 | max = PATH_MAX; |
| 183 | goto recopy; |
| 184 | } |
| 185 | |
| 186 | /* The empty path is special. */ |
| 187 | if (unlikely(!len)) { |
| 188 | if (empty) |
| 189 | *empty = 1; |
| 190 | err = ERR_PTR(-ENOENT); |
| 191 | if (!(flags & LOOKUP_EMPTY)) |
| 192 | goto error; |
| 193 | } |
| 194 | |
| 195 | err = ERR_PTR(-ENAMETOOLONG); |
| 196 | if (unlikely(len >= PATH_MAX)) |
| 197 | goto error; |
| 198 | |
| 199 | result->uptr = filename; |
| 200 | result->aname = NULL; |
| 201 | audit_getname(result); |
| 202 | return result; |
| 203 | |
| 204 | error: |
| 205 | final_putname(result); |
| 206 | return err; |
| 207 | } |
| 208 | |
| 209 | struct filename * |
| 210 | getname(const char __user * filename) |
| 211 | { |
| 212 | return getname_flags(filename, 0, NULL); |
| 213 | } |
| 214 | |
| 215 | /* |
| 216 | * The "getname_kernel()" interface doesn't do pathnames longer |
| 217 | * than EMBEDDED_NAME_MAX. Deal with it - you're a kernel user. |
| 218 | */ |
| 219 | struct filename * |
| 220 | getname_kernel(const char * filename) |
| 221 | { |
| 222 | struct filename *result; |
| 223 | char *kname; |
| 224 | int len; |
| 225 | |
| 226 | len = strlen(filename); |
| 227 | if (len >= EMBEDDED_NAME_MAX) |
| 228 | return ERR_PTR(-ENAMETOOLONG); |
| 229 | |
| 230 | result = __getname(); |
| 231 | if (unlikely(!result)) |
| 232 | return ERR_PTR(-ENOMEM); |
| 233 | |
| 234 | kname = (char *)result + sizeof(*result); |
| 235 | result->name = kname; |
| 236 | result->uptr = NULL; |
| 237 | result->aname = NULL; |
| 238 | result->separate = false; |
| 239 | |
| 240 | strlcpy(kname, filename, EMBEDDED_NAME_MAX); |
| 241 | return result; |
| 242 | } |
| 243 | |
| 244 | #ifdef CONFIG_AUDITSYSCALL |
| 245 | void putname(struct filename *name) |
| 246 | { |
| 247 | if (unlikely(!audit_dummy_context())) |
| 248 | return audit_putname(name); |
| 249 | final_putname(name); |
| 250 | } |
| 251 | #endif |
| 252 | |
| 253 | static int check_acl(struct inode *inode, int mask) |
| 254 | { |
| 255 | #ifdef CONFIG_FS_POSIX_ACL |
| 256 | struct posix_acl *acl; |
| 257 | |
| 258 | if (mask & MAY_NOT_BLOCK) { |
| 259 | acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS); |
| 260 | if (!acl) |
| 261 | return -EAGAIN; |
| 262 | /* no ->get_acl() calls in RCU mode... */ |
| 263 | if (acl == ACL_NOT_CACHED) |
| 264 | return -ECHILD; |
| 265 | return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK); |
| 266 | } |
| 267 | |
| 268 | acl = get_acl(inode, ACL_TYPE_ACCESS); |
| 269 | if (IS_ERR(acl)) |
| 270 | return PTR_ERR(acl); |
| 271 | if (acl) { |
| 272 | int error = posix_acl_permission(inode, acl, mask); |
| 273 | posix_acl_release(acl); |
| 274 | return error; |
| 275 | } |
| 276 | #endif |
| 277 | |
| 278 | return -EAGAIN; |
| 279 | } |
| 280 | |
| 281 | /* |
| 282 | * This does the basic permission checking |
| 283 | */ |
| 284 | static int acl_permission_check(struct inode *inode, int mask) |
| 285 | { |
| 286 | unsigned int mode = inode->i_mode; |
| 287 | |
| 288 | if (likely(uid_eq(current_fsuid(), inode->i_uid))) |
| 289 | mode >>= 6; |
| 290 | else { |
| 291 | if (IS_POSIXACL(inode) && (mode & S_IRWXG)) { |
| 292 | int error = check_acl(inode, mask); |
| 293 | if (error != -EAGAIN) |
| 294 | return error; |
| 295 | } |
| 296 | |
| 297 | if (in_group_p(inode->i_gid)) |
| 298 | mode >>= 3; |
| 299 | } |
| 300 | |
| 301 | /* |
| 302 | * If the DACs are ok we don't need any capability check. |
| 303 | */ |
| 304 | if ((mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0) |
| 305 | return 0; |
| 306 | return -EACCES; |
| 307 | } |
| 308 | |
| 309 | /** |
| 310 | * generic_permission - check for access rights on a Posix-like filesystem |
| 311 | * @inode: inode to check access rights for |
| 312 | * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...) |
| 313 | * |
| 314 | * Used to check for read/write/execute permissions on a file. |
| 315 | * We use "fsuid" for this, letting us set arbitrary permissions |
| 316 | * for filesystem access without changing the "normal" uids which |
| 317 | * are used for other things. |
| 318 | * |
| 319 | * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk |
| 320 | * request cannot be satisfied (eg. requires blocking or too much complexity). |
| 321 | * It would then be called again in ref-walk mode. |
| 322 | */ |
| 323 | int generic_permission(struct inode *inode, int mask) |
| 324 | { |
| 325 | int ret; |
| 326 | |
| 327 | /* |
| 328 | * Do the basic permission checks. |
| 329 | */ |
| 330 | ret = acl_permission_check(inode, mask); |
| 331 | if (ret != -EACCES) |
| 332 | return ret; |
| 333 | |
| 334 | if (S_ISDIR(inode->i_mode)) { |
| 335 | /* DACs are overridable for directories */ |
| 336 | if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE)) |
| 337 | return 0; |
| 338 | if (!(mask & MAY_WRITE)) |
| 339 | if (capable_wrt_inode_uidgid(inode, |
| 340 | CAP_DAC_READ_SEARCH)) |
| 341 | return 0; |
| 342 | return -EACCES; |
| 343 | } |
| 344 | /* |
| 345 | * Read/write DACs are always overridable. |
| 346 | * Executable DACs are overridable when there is |
| 347 | * at least one exec bit set. |
| 348 | */ |
| 349 | if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO)) |
| 350 | if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE)) |
| 351 | return 0; |
| 352 | |
| 353 | /* |
| 354 | * Searching includes executable on directories, else just read. |
| 355 | */ |
| 356 | mask &= MAY_READ | MAY_WRITE | MAY_EXEC; |
| 357 | if (mask == MAY_READ) |
| 358 | if (capable_wrt_inode_uidgid(inode, CAP_DAC_READ_SEARCH)) |
| 359 | return 0; |
| 360 | |
| 361 | return -EACCES; |
| 362 | } |
| 363 | EXPORT_SYMBOL(generic_permission); |
| 364 | |
| 365 | /* |
| 366 | * We _really_ want to just do "generic_permission()" without |
| 367 | * even looking at the inode->i_op values. So we keep a cache |
| 368 | * flag in inode->i_opflags, that says "this has not special |
| 369 | * permission function, use the fast case". |
| 370 | */ |
| 371 | static inline int do_inode_permission(struct inode *inode, int mask) |
| 372 | { |
| 373 | if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) { |
| 374 | if (likely(inode->i_op->permission)) |
| 375 | return inode->i_op->permission(inode, mask); |
| 376 | |
| 377 | /* This gets set once for the inode lifetime */ |
| 378 | spin_lock(&inode->i_lock); |
| 379 | inode->i_opflags |= IOP_FASTPERM; |
| 380 | spin_unlock(&inode->i_lock); |
| 381 | } |
| 382 | return generic_permission(inode, mask); |
| 383 | } |
| 384 | |
| 385 | /** |
| 386 | * __inode_permission - Check for access rights to a given inode |
| 387 | * @inode: Inode to check permission on |
| 388 | * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) |
| 389 | * |
| 390 | * Check for read/write/execute permissions on an inode. |
| 391 | * |
| 392 | * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask. |
| 393 | * |
| 394 | * This does not check for a read-only file system. You probably want |
| 395 | * inode_permission(). |
| 396 | */ |
| 397 | int __inode_permission(struct inode *inode, int mask) |
| 398 | { |
| 399 | int retval; |
| 400 | |
| 401 | if (unlikely(mask & MAY_WRITE)) { |
| 402 | /* |
| 403 | * Nobody gets write access to an immutable file. |
| 404 | */ |
| 405 | if (IS_IMMUTABLE(inode)) |
| 406 | return -EACCES; |
| 407 | } |
| 408 | |
| 409 | retval = do_inode_permission(inode, mask); |
| 410 | if (retval) |
| 411 | return retval; |
| 412 | |
| 413 | retval = devcgroup_inode_permission(inode, mask); |
| 414 | if (retval) |
| 415 | return retval; |
| 416 | |
| 417 | return security_inode_permission(inode, mask); |
| 418 | } |
| 419 | EXPORT_SYMBOL(__inode_permission); |
| 420 | |
| 421 | /** |
| 422 | * sb_permission - Check superblock-level permissions |
| 423 | * @sb: Superblock of inode to check permission on |
| 424 | * @inode: Inode to check permission on |
| 425 | * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) |
| 426 | * |
| 427 | * Separate out file-system wide checks from inode-specific permission checks. |
| 428 | */ |
| 429 | static int sb_permission(struct super_block *sb, struct inode *inode, int mask) |
| 430 | { |
| 431 | if (unlikely(mask & MAY_WRITE)) { |
| 432 | umode_t mode = inode->i_mode; |
| 433 | |
| 434 | /* Nobody gets write access to a read-only fs. */ |
| 435 | if ((sb->s_flags & MS_RDONLY) && |
| 436 | (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) |
| 437 | return -EROFS; |
| 438 | } |
| 439 | return 0; |
| 440 | } |
| 441 | |
| 442 | /** |
| 443 | * inode_permission - Check for access rights to a given inode |
| 444 | * @inode: Inode to check permission on |
| 445 | * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) |
| 446 | * |
| 447 | * Check for read/write/execute permissions on an inode. We use fs[ug]id for |
| 448 | * this, letting us set arbitrary permissions for filesystem access without |
| 449 | * changing the "normal" UIDs which are used for other things. |
| 450 | * |
| 451 | * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask. |
| 452 | */ |
| 453 | int inode_permission(struct inode *inode, int mask) |
| 454 | { |
| 455 | int retval; |
| 456 | |
| 457 | retval = sb_permission(inode->i_sb, inode, mask); |
| 458 | if (retval) |
| 459 | return retval; |
| 460 | return __inode_permission(inode, mask); |
| 461 | } |
| 462 | EXPORT_SYMBOL(inode_permission); |
| 463 | |
| 464 | /** |
| 465 | * path_get - get a reference to a path |
| 466 | * @path: path to get the reference to |
| 467 | * |
| 468 | * Given a path increment the reference count to the dentry and the vfsmount. |
| 469 | */ |
| 470 | void path_get(const struct path *path) |
| 471 | { |
| 472 | mntget(path->mnt); |
| 473 | dget(path->dentry); |
| 474 | } |
| 475 | EXPORT_SYMBOL(path_get); |
| 476 | |
| 477 | /** |
| 478 | * path_put - put a reference to a path |
| 479 | * @path: path to put the reference to |
| 480 | * |
| 481 | * Given a path decrement the reference count to the dentry and the vfsmount. |
| 482 | */ |
| 483 | void path_put(const struct path *path) |
| 484 | { |
| 485 | dput(path->dentry); |
| 486 | mntput(path->mnt); |
| 487 | } |
| 488 | EXPORT_SYMBOL(path_put); |
| 489 | |
| 490 | struct nameidata { |
| 491 | struct path path; |
| 492 | struct qstr last; |
| 493 | struct path root; |
| 494 | struct inode *inode; /* path.dentry.d_inode */ |
| 495 | unsigned int flags; |
| 496 | unsigned seq, m_seq; |
| 497 | int last_type; |
| 498 | unsigned depth; |
| 499 | struct file *base; |
| 500 | char *saved_names[MAX_NESTED_LINKS + 1]; |
| 501 | }; |
| 502 | |
| 503 | /* |
| 504 | * Path walking has 2 modes, rcu-walk and ref-walk (see |
| 505 | * Documentation/filesystems/path-lookup.txt). In situations when we can't |
| 506 | * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab |
| 507 | * normal reference counts on dentries and vfsmounts to transition to rcu-walk |
| 508 | * mode. Refcounts are grabbed at the last known good point before rcu-walk |
| 509 | * got stuck, so ref-walk may continue from there. If this is not successful |
| 510 | * (eg. a seqcount has changed), then failure is returned and it's up to caller |
| 511 | * to restart the path walk from the beginning in ref-walk mode. |
| 512 | */ |
| 513 | |
| 514 | /** |
| 515 | * unlazy_walk - try to switch to ref-walk mode. |
| 516 | * @nd: nameidata pathwalk data |
| 517 | * @dentry: child of nd->path.dentry or NULL |
| 518 | * Returns: 0 on success, -ECHILD on failure |
| 519 | * |
| 520 | * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry |
| 521 | * for ref-walk mode. @dentry must be a path found by a do_lookup call on |
| 522 | * @nd or NULL. Must be called from rcu-walk context. |
| 523 | */ |
| 524 | static int unlazy_walk(struct nameidata *nd, struct dentry *dentry) |
| 525 | { |
| 526 | struct fs_struct *fs = current->fs; |
| 527 | struct dentry *parent = nd->path.dentry; |
| 528 | |
| 529 | BUG_ON(!(nd->flags & LOOKUP_RCU)); |
| 530 | |
| 531 | /* |
| 532 | * After legitimizing the bastards, terminate_walk() |
| 533 | * will do the right thing for non-RCU mode, and all our |
| 534 | * subsequent exit cases should rcu_read_unlock() |
| 535 | * before returning. Do vfsmount first; if dentry |
| 536 | * can't be legitimized, just set nd->path.dentry to NULL |
| 537 | * and rely on dput(NULL) being a no-op. |
| 538 | */ |
| 539 | if (!legitimize_mnt(nd->path.mnt, nd->m_seq)) |
| 540 | return -ECHILD; |
| 541 | nd->flags &= ~LOOKUP_RCU; |
| 542 | |
| 543 | if (!lockref_get_not_dead(&parent->d_lockref)) { |
| 544 | nd->path.dentry = NULL; |
| 545 | goto out; |
| 546 | } |
| 547 | |
| 548 | /* |
| 549 | * For a negative lookup, the lookup sequence point is the parents |
| 550 | * sequence point, and it only needs to revalidate the parent dentry. |
| 551 | * |
| 552 | * For a positive lookup, we need to move both the parent and the |
| 553 | * dentry from the RCU domain to be properly refcounted. And the |
| 554 | * sequence number in the dentry validates *both* dentry counters, |
| 555 | * since we checked the sequence number of the parent after we got |
| 556 | * the child sequence number. So we know the parent must still |
| 557 | * be valid if the child sequence number is still valid. |
| 558 | */ |
| 559 | if (!dentry) { |
| 560 | if (read_seqcount_retry(&parent->d_seq, nd->seq)) |
| 561 | goto out; |
| 562 | BUG_ON(nd->inode != parent->d_inode); |
| 563 | } else { |
| 564 | if (!lockref_get_not_dead(&dentry->d_lockref)) |
| 565 | goto out; |
| 566 | if (read_seqcount_retry(&dentry->d_seq, nd->seq)) |
| 567 | goto drop_dentry; |
| 568 | } |
| 569 | |
| 570 | /* |
| 571 | * Sequence counts matched. Now make sure that the root is |
| 572 | * still valid and get it if required. |
| 573 | */ |
| 574 | if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) { |
| 575 | spin_lock(&fs->lock); |
| 576 | if (nd->root.mnt != fs->root.mnt || nd->root.dentry != fs->root.dentry) |
| 577 | goto unlock_and_drop_dentry; |
| 578 | path_get(&nd->root); |
| 579 | spin_unlock(&fs->lock); |
| 580 | } |
| 581 | |
| 582 | rcu_read_unlock(); |
| 583 | return 0; |
| 584 | |
| 585 | unlock_and_drop_dentry: |
| 586 | spin_unlock(&fs->lock); |
| 587 | drop_dentry: |
| 588 | rcu_read_unlock(); |
| 589 | dput(dentry); |
| 590 | goto drop_root_mnt; |
| 591 | out: |
| 592 | rcu_read_unlock(); |
| 593 | drop_root_mnt: |
| 594 | if (!(nd->flags & LOOKUP_ROOT)) |
| 595 | nd->root.mnt = NULL; |
| 596 | return -ECHILD; |
| 597 | } |
| 598 | |
| 599 | static inline int d_revalidate(struct dentry *dentry, unsigned int flags) |
| 600 | { |
| 601 | return dentry->d_op->d_revalidate(dentry, flags); |
| 602 | } |
| 603 | |
| 604 | /** |
| 605 | * complete_walk - successful completion of path walk |
| 606 | * @nd: pointer nameidata |
| 607 | * |
| 608 | * If we had been in RCU mode, drop out of it and legitimize nd->path. |
| 609 | * Revalidate the final result, unless we'd already done that during |
| 610 | * the path walk or the filesystem doesn't ask for it. Return 0 on |
| 611 | * success, -error on failure. In case of failure caller does not |
| 612 | * need to drop nd->path. |
| 613 | */ |
| 614 | static int complete_walk(struct nameidata *nd) |
| 615 | { |
| 616 | struct dentry *dentry = nd->path.dentry; |
| 617 | int status; |
| 618 | |
| 619 | if (nd->flags & LOOKUP_RCU) { |
| 620 | nd->flags &= ~LOOKUP_RCU; |
| 621 | if (!(nd->flags & LOOKUP_ROOT)) |
| 622 | nd->root.mnt = NULL; |
| 623 | |
| 624 | if (!legitimize_mnt(nd->path.mnt, nd->m_seq)) { |
| 625 | rcu_read_unlock(); |
| 626 | return -ECHILD; |
| 627 | } |
| 628 | if (unlikely(!lockref_get_not_dead(&dentry->d_lockref))) { |
| 629 | rcu_read_unlock(); |
| 630 | mntput(nd->path.mnt); |
| 631 | return -ECHILD; |
| 632 | } |
| 633 | if (read_seqcount_retry(&dentry->d_seq, nd->seq)) { |
| 634 | rcu_read_unlock(); |
| 635 | dput(dentry); |
| 636 | mntput(nd->path.mnt); |
| 637 | return -ECHILD; |
| 638 | } |
| 639 | rcu_read_unlock(); |
| 640 | } |
| 641 | |
| 642 | if (likely(!(nd->flags & LOOKUP_JUMPED))) |
| 643 | return 0; |
| 644 | |
| 645 | if (likely(!(dentry->d_flags & DCACHE_OP_WEAK_REVALIDATE))) |
| 646 | return 0; |
| 647 | |
| 648 | status = dentry->d_op->d_weak_revalidate(dentry, nd->flags); |
| 649 | if (status > 0) |
| 650 | return 0; |
| 651 | |
| 652 | if (!status) |
| 653 | status = -ESTALE; |
| 654 | |
| 655 | path_put(&nd->path); |
| 656 | return status; |
| 657 | } |
| 658 | |
| 659 | static __always_inline void set_root(struct nameidata *nd) |
| 660 | { |
| 661 | get_fs_root(current->fs, &nd->root); |
| 662 | } |
| 663 | |
| 664 | static int link_path_walk(const char *, struct nameidata *); |
| 665 | |
| 666 | static __always_inline unsigned set_root_rcu(struct nameidata *nd) |
| 667 | { |
| 668 | struct fs_struct *fs = current->fs; |
| 669 | unsigned seq, res; |
| 670 | |
| 671 | do { |
| 672 | seq = read_seqcount_begin(&fs->seq); |
| 673 | nd->root = fs->root; |
| 674 | res = __read_seqcount_begin(&nd->root.dentry->d_seq); |
| 675 | } while (read_seqcount_retry(&fs->seq, seq)); |
| 676 | return res; |
| 677 | } |
| 678 | |
| 679 | static void path_put_conditional(struct path *path, struct nameidata *nd) |
| 680 | { |
| 681 | dput(path->dentry); |
| 682 | if (path->mnt != nd->path.mnt) |
| 683 | mntput(path->mnt); |
| 684 | } |
| 685 | |
| 686 | static inline void path_to_nameidata(const struct path *path, |
| 687 | struct nameidata *nd) |
| 688 | { |
| 689 | if (!(nd->flags & LOOKUP_RCU)) { |
| 690 | dput(nd->path.dentry); |
| 691 | if (nd->path.mnt != path->mnt) |
| 692 | mntput(nd->path.mnt); |
| 693 | } |
| 694 | nd->path.mnt = path->mnt; |
| 695 | nd->path.dentry = path->dentry; |
| 696 | } |
| 697 | |
| 698 | /* |
| 699 | * Helper to directly jump to a known parsed path from ->follow_link, |
| 700 | * caller must have taken a reference to path beforehand. |
| 701 | */ |
| 702 | void nd_jump_link(struct nameidata *nd, struct path *path) |
| 703 | { |
| 704 | path_put(&nd->path); |
| 705 | |
| 706 | nd->path = *path; |
| 707 | nd->inode = nd->path.dentry->d_inode; |
| 708 | nd->flags |= LOOKUP_JUMPED; |
| 709 | } |
| 710 | |
| 711 | void nd_set_link(struct nameidata *nd, char *path) |
| 712 | { |
| 713 | nd->saved_names[nd->depth] = path; |
| 714 | } |
| 715 | EXPORT_SYMBOL(nd_set_link); |
| 716 | |
| 717 | char *nd_get_link(struct nameidata *nd) |
| 718 | { |
| 719 | return nd->saved_names[nd->depth]; |
| 720 | } |
| 721 | EXPORT_SYMBOL(nd_get_link); |
| 722 | |
| 723 | static inline void put_link(struct nameidata *nd, struct path *link, void *cookie) |
| 724 | { |
| 725 | struct inode *inode = link->dentry->d_inode; |
| 726 | if (inode->i_op->put_link) |
| 727 | inode->i_op->put_link(link->dentry, nd, cookie); |
| 728 | path_put(link); |
| 729 | } |
| 730 | |
| 731 | int sysctl_protected_symlinks __read_mostly = 0; |
| 732 | int sysctl_protected_hardlinks __read_mostly = 0; |
| 733 | |
| 734 | /** |
| 735 | * may_follow_link - Check symlink following for unsafe situations |
| 736 | * @link: The path of the symlink |
| 737 | * @nd: nameidata pathwalk data |
| 738 | * |
| 739 | * In the case of the sysctl_protected_symlinks sysctl being enabled, |
| 740 | * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is |
| 741 | * in a sticky world-writable directory. This is to protect privileged |
| 742 | * processes from failing races against path names that may change out |
| 743 | * from under them by way of other users creating malicious symlinks. |
| 744 | * It will permit symlinks to be followed only when outside a sticky |
| 745 | * world-writable directory, or when the uid of the symlink and follower |
| 746 | * match, or when the directory owner matches the symlink's owner. |
| 747 | * |
| 748 | * Returns 0 if following the symlink is allowed, -ve on error. |
| 749 | */ |
| 750 | static inline int may_follow_link(struct path *link, struct nameidata *nd) |
| 751 | { |
| 752 | const struct inode *inode; |
| 753 | const struct inode *parent; |
| 754 | |
| 755 | if (!sysctl_protected_symlinks) |
| 756 | return 0; |
| 757 | |
| 758 | /* Allowed if owner and follower match. */ |
| 759 | inode = link->dentry->d_inode; |
| 760 | if (uid_eq(current_cred()->fsuid, inode->i_uid)) |
| 761 | return 0; |
| 762 | |
| 763 | /* Allowed if parent directory not sticky and world-writable. */ |
| 764 | parent = nd->path.dentry->d_inode; |
| 765 | if ((parent->i_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH)) |
| 766 | return 0; |
| 767 | |
| 768 | /* Allowed if parent directory and link owner match. */ |
| 769 | if (uid_eq(parent->i_uid, inode->i_uid)) |
| 770 | return 0; |
| 771 | |
| 772 | audit_log_link_denied("follow_link", link); |
| 773 | path_put_conditional(link, nd); |
| 774 | path_put(&nd->path); |
| 775 | return -EACCES; |
| 776 | } |
| 777 | |
| 778 | /** |
| 779 | * safe_hardlink_source - Check for safe hardlink conditions |
| 780 | * @inode: the source inode to hardlink from |
| 781 | * |
| 782 | * Return false if at least one of the following conditions: |
| 783 | * - inode is not a regular file |
| 784 | * - inode is setuid |
| 785 | * - inode is setgid and group-exec |
| 786 | * - access failure for read and write |
| 787 | * |
| 788 | * Otherwise returns true. |
| 789 | */ |
| 790 | static bool safe_hardlink_source(struct inode *inode) |
| 791 | { |
| 792 | umode_t mode = inode->i_mode; |
| 793 | |
| 794 | /* Special files should not get pinned to the filesystem. */ |
| 795 | if (!S_ISREG(mode)) |
| 796 | return false; |
| 797 | |
| 798 | /* Setuid files should not get pinned to the filesystem. */ |
| 799 | if (mode & S_ISUID) |
| 800 | return false; |
| 801 | |
| 802 | /* Executable setgid files should not get pinned to the filesystem. */ |
| 803 | if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) |
| 804 | return false; |
| 805 | |
| 806 | /* Hardlinking to unreadable or unwritable sources is dangerous. */ |
| 807 | if (inode_permission(inode, MAY_READ | MAY_WRITE)) |
| 808 | return false; |
| 809 | |
| 810 | return true; |
| 811 | } |
| 812 | |
| 813 | /** |
| 814 | * may_linkat - Check permissions for creating a hardlink |
| 815 | * @link: the source to hardlink from |
| 816 | * |
| 817 | * Block hardlink when all of: |
| 818 | * - sysctl_protected_hardlinks enabled |
| 819 | * - fsuid does not match inode |
| 820 | * - hardlink source is unsafe (see safe_hardlink_source() above) |
| 821 | * - not CAP_FOWNER |
| 822 | * |
| 823 | * Returns 0 if successful, -ve on error. |
| 824 | */ |
| 825 | static int may_linkat(struct path *link) |
| 826 | { |
| 827 | const struct cred *cred; |
| 828 | struct inode *inode; |
| 829 | |
| 830 | if (!sysctl_protected_hardlinks) |
| 831 | return 0; |
| 832 | |
| 833 | cred = current_cred(); |
| 834 | inode = link->dentry->d_inode; |
| 835 | |
| 836 | /* Source inode owner (or CAP_FOWNER) can hardlink all they like, |
| 837 | * otherwise, it must be a safe source. |
| 838 | */ |
| 839 | if (uid_eq(cred->fsuid, inode->i_uid) || safe_hardlink_source(inode) || |
| 840 | capable(CAP_FOWNER)) |
| 841 | return 0; |
| 842 | |
| 843 | audit_log_link_denied("linkat", link); |
| 844 | return -EPERM; |
| 845 | } |
| 846 | |
| 847 | static __always_inline int |
| 848 | follow_link(struct path *link, struct nameidata *nd, void **p) |
| 849 | { |
| 850 | struct dentry *dentry = link->dentry; |
| 851 | int error; |
| 852 | char *s; |
| 853 | |
| 854 | BUG_ON(nd->flags & LOOKUP_RCU); |
| 855 | |
| 856 | if (link->mnt == nd->path.mnt) |
| 857 | mntget(link->mnt); |
| 858 | |
| 859 | error = -ELOOP; |
| 860 | if (unlikely(current->total_link_count >= 40)) |
| 861 | goto out_put_nd_path; |
| 862 | |
| 863 | cond_resched(); |
| 864 | current->total_link_count++; |
| 865 | |
| 866 | touch_atime(link); |
| 867 | nd_set_link(nd, NULL); |
| 868 | |
| 869 | error = security_inode_follow_link(link->dentry, nd); |
| 870 | if (error) |
| 871 | goto out_put_nd_path; |
| 872 | |
| 873 | nd->last_type = LAST_BIND; |
| 874 | *p = dentry->d_inode->i_op->follow_link(dentry, nd); |
| 875 | error = PTR_ERR(*p); |
| 876 | if (IS_ERR(*p)) |
| 877 | goto out_put_nd_path; |
| 878 | |
| 879 | error = 0; |
| 880 | s = nd_get_link(nd); |
| 881 | if (s) { |
| 882 | if (unlikely(IS_ERR(s))) { |
| 883 | path_put(&nd->path); |
| 884 | put_link(nd, link, *p); |
| 885 | return PTR_ERR(s); |
| 886 | } |
| 887 | if (*s == '/') { |
| 888 | if (!nd->root.mnt) |
| 889 | set_root(nd); |
| 890 | path_put(&nd->path); |
| 891 | nd->path = nd->root; |
| 892 | path_get(&nd->root); |
| 893 | nd->flags |= LOOKUP_JUMPED; |
| 894 | } |
| 895 | nd->inode = nd->path.dentry->d_inode; |
| 896 | error = link_path_walk(s, nd); |
| 897 | if (unlikely(error)) |
| 898 | put_link(nd, link, *p); |
| 899 | } |
| 900 | |
| 901 | return error; |
| 902 | |
| 903 | out_put_nd_path: |
| 904 | *p = NULL; |
| 905 | path_put(&nd->path); |
| 906 | path_put(link); |
| 907 | return error; |
| 908 | } |
| 909 | |
| 910 | static int follow_up_rcu(struct path *path) |
| 911 | { |
| 912 | struct mount *mnt = real_mount(path->mnt); |
| 913 | struct mount *parent; |
| 914 | struct dentry *mountpoint; |
| 915 | |
| 916 | parent = mnt->mnt_parent; |
| 917 | if (&parent->mnt == path->mnt) |
| 918 | return 0; |
| 919 | mountpoint = mnt->mnt_mountpoint; |
| 920 | path->dentry = mountpoint; |
| 921 | path->mnt = &parent->mnt; |
| 922 | return 1; |
| 923 | } |
| 924 | |
| 925 | /* |
| 926 | * follow_up - Find the mountpoint of path's vfsmount |
| 927 | * |
| 928 | * Given a path, find the mountpoint of its source file system. |
| 929 | * Replace @path with the path of the mountpoint in the parent mount. |
| 930 | * Up is towards /. |
| 931 | * |
| 932 | * Return 1 if we went up a level and 0 if we were already at the |
| 933 | * root. |
| 934 | */ |
| 935 | int follow_up(struct path *path) |
| 936 | { |
| 937 | struct mount *mnt = real_mount(path->mnt); |
| 938 | struct mount *parent; |
| 939 | struct dentry *mountpoint; |
| 940 | |
| 941 | read_seqlock_excl(&mount_lock); |
| 942 | parent = mnt->mnt_parent; |
| 943 | if (parent == mnt) { |
| 944 | read_sequnlock_excl(&mount_lock); |
| 945 | return 0; |
| 946 | } |
| 947 | mntget(&parent->mnt); |
| 948 | mountpoint = dget(mnt->mnt_mountpoint); |
| 949 | read_sequnlock_excl(&mount_lock); |
| 950 | dput(path->dentry); |
| 951 | path->dentry = mountpoint; |
| 952 | mntput(path->mnt); |
| 953 | path->mnt = &parent->mnt; |
| 954 | return 1; |
| 955 | } |
| 956 | EXPORT_SYMBOL(follow_up); |
| 957 | |
| 958 | /* |
| 959 | * Perform an automount |
| 960 | * - return -EISDIR to tell follow_managed() to stop and return the path we |
| 961 | * were called with. |
| 962 | */ |
| 963 | static int follow_automount(struct path *path, unsigned flags, |
| 964 | bool *need_mntput) |
| 965 | { |
| 966 | struct vfsmount *mnt; |
| 967 | int err; |
| 968 | |
| 969 | if (!path->dentry->d_op || !path->dentry->d_op->d_automount) |
| 970 | return -EREMOTE; |
| 971 | |
| 972 | /* We don't want to mount if someone's just doing a stat - |
| 973 | * unless they're stat'ing a directory and appended a '/' to |
| 974 | * the name. |
| 975 | * |
| 976 | * We do, however, want to mount if someone wants to open or |
| 977 | * create a file of any type under the mountpoint, wants to |
| 978 | * traverse through the mountpoint or wants to open the |
| 979 | * mounted directory. Also, autofs may mark negative dentries |
| 980 | * as being automount points. These will need the attentions |
| 981 | * of the daemon to instantiate them before they can be used. |
| 982 | */ |
| 983 | if (!(flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY | |
| 984 | LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) && |
| 985 | path->dentry->d_inode) |
| 986 | return -EISDIR; |
| 987 | |
| 988 | current->total_link_count++; |
| 989 | if (current->total_link_count >= 40) |
| 990 | return -ELOOP; |
| 991 | |
| 992 | mnt = path->dentry->d_op->d_automount(path); |
| 993 | if (IS_ERR(mnt)) { |
| 994 | /* |
| 995 | * The filesystem is allowed to return -EISDIR here to indicate |
| 996 | * it doesn't want to automount. For instance, autofs would do |
| 997 | * this so that its userspace daemon can mount on this dentry. |
| 998 | * |
| 999 | * However, we can only permit this if it's a terminal point in |
| 1000 | * the path being looked up; if it wasn't then the remainder of |
| 1001 | * the path is inaccessible and we should say so. |
| 1002 | */ |
| 1003 | if (PTR_ERR(mnt) == -EISDIR && (flags & LOOKUP_PARENT)) |
| 1004 | return -EREMOTE; |
| 1005 | return PTR_ERR(mnt); |
| 1006 | } |
| 1007 | |
| 1008 | if (!mnt) /* mount collision */ |
| 1009 | return 0; |
| 1010 | |
| 1011 | if (!*need_mntput) { |
| 1012 | /* lock_mount() may release path->mnt on error */ |
| 1013 | mntget(path->mnt); |
| 1014 | *need_mntput = true; |
| 1015 | } |
| 1016 | err = finish_automount(mnt, path); |
| 1017 | |
| 1018 | switch (err) { |
| 1019 | case -EBUSY: |
| 1020 | /* Someone else made a mount here whilst we were busy */ |
| 1021 | return 0; |
| 1022 | case 0: |
| 1023 | path_put(path); |
| 1024 | path->mnt = mnt; |
| 1025 | path->dentry = dget(mnt->mnt_root); |
| 1026 | return 0; |
| 1027 | default: |
| 1028 | return err; |
| 1029 | } |
| 1030 | |
| 1031 | } |
| 1032 | |
| 1033 | /* |
| 1034 | * Handle a dentry that is managed in some way. |
| 1035 | * - Flagged for transit management (autofs) |
| 1036 | * - Flagged as mountpoint |
| 1037 | * - Flagged as automount point |
| 1038 | * |
| 1039 | * This may only be called in refwalk mode. |
| 1040 | * |
| 1041 | * Serialization is taken care of in namespace.c |
| 1042 | */ |
| 1043 | static int follow_managed(struct path *path, unsigned flags) |
| 1044 | { |
| 1045 | struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */ |
| 1046 | unsigned managed; |
| 1047 | bool need_mntput = false; |
| 1048 | int ret = 0; |
| 1049 | |
| 1050 | /* Given that we're not holding a lock here, we retain the value in a |
| 1051 | * local variable for each dentry as we look at it so that we don't see |
| 1052 | * the components of that value change under us */ |
| 1053 | while (managed = ACCESS_ONCE(path->dentry->d_flags), |
| 1054 | managed &= DCACHE_MANAGED_DENTRY, |
| 1055 | unlikely(managed != 0)) { |
| 1056 | /* Allow the filesystem to manage the transit without i_mutex |
| 1057 | * being held. */ |
| 1058 | if (managed & DCACHE_MANAGE_TRANSIT) { |
| 1059 | BUG_ON(!path->dentry->d_op); |
| 1060 | BUG_ON(!path->dentry->d_op->d_manage); |
| 1061 | ret = path->dentry->d_op->d_manage(path->dentry, false); |
| 1062 | if (ret < 0) |
| 1063 | break; |
| 1064 | } |
| 1065 | |
| 1066 | /* Transit to a mounted filesystem. */ |
| 1067 | if (managed & DCACHE_MOUNTED) { |
| 1068 | struct vfsmount *mounted = lookup_mnt(path); |
| 1069 | if (mounted) { |
| 1070 | dput(path->dentry); |
| 1071 | if (need_mntput) |
| 1072 | mntput(path->mnt); |
| 1073 | path->mnt = mounted; |
| 1074 | path->dentry = dget(mounted->mnt_root); |
| 1075 | need_mntput = true; |
| 1076 | continue; |
| 1077 | } |
| 1078 | |
| 1079 | /* Something is mounted on this dentry in another |
| 1080 | * namespace and/or whatever was mounted there in this |
| 1081 | * namespace got unmounted before lookup_mnt() could |
| 1082 | * get it */ |
| 1083 | } |
| 1084 | |
| 1085 | /* Handle an automount point */ |
| 1086 | if (managed & DCACHE_NEED_AUTOMOUNT) { |
| 1087 | ret = follow_automount(path, flags, &need_mntput); |
| 1088 | if (ret < 0) |
| 1089 | break; |
| 1090 | continue; |
| 1091 | } |
| 1092 | |
| 1093 | /* We didn't change the current path point */ |
| 1094 | break; |
| 1095 | } |
| 1096 | |
| 1097 | if (need_mntput && path->mnt == mnt) |
| 1098 | mntput(path->mnt); |
| 1099 | if (ret == -EISDIR) |
| 1100 | ret = 0; |
| 1101 | return ret < 0 ? ret : need_mntput; |
| 1102 | } |
| 1103 | |
| 1104 | int follow_down_one(struct path *path) |
| 1105 | { |
| 1106 | struct vfsmount *mounted; |
| 1107 | |
| 1108 | mounted = lookup_mnt(path); |
| 1109 | if (mounted) { |
| 1110 | dput(path->dentry); |
| 1111 | mntput(path->mnt); |
| 1112 | path->mnt = mounted; |
| 1113 | path->dentry = dget(mounted->mnt_root); |
| 1114 | return 1; |
| 1115 | } |
| 1116 | return 0; |
| 1117 | } |
| 1118 | EXPORT_SYMBOL(follow_down_one); |
| 1119 | |
| 1120 | static inline int managed_dentry_rcu(struct dentry *dentry) |
| 1121 | { |
| 1122 | return (dentry->d_flags & DCACHE_MANAGE_TRANSIT) ? |
| 1123 | dentry->d_op->d_manage(dentry, true) : 0; |
| 1124 | } |
| 1125 | |
| 1126 | /* |
| 1127 | * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if |
| 1128 | * we meet a managed dentry that would need blocking. |
| 1129 | */ |
| 1130 | static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, |
| 1131 | struct inode **inode) |
| 1132 | { |
| 1133 | for (;;) { |
| 1134 | struct mount *mounted; |
| 1135 | /* |
| 1136 | * Don't forget we might have a non-mountpoint managed dentry |
| 1137 | * that wants to block transit. |
| 1138 | */ |
| 1139 | switch (managed_dentry_rcu(path->dentry)) { |
| 1140 | case -ECHILD: |
| 1141 | default: |
| 1142 | return false; |
| 1143 | case -EISDIR: |
| 1144 | return true; |
| 1145 | case 0: |
| 1146 | break; |
| 1147 | } |
| 1148 | |
| 1149 | if (!d_mountpoint(path->dentry)) |
| 1150 | return !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT); |
| 1151 | |
| 1152 | mounted = __lookup_mnt(path->mnt, path->dentry); |
| 1153 | if (!mounted) |
| 1154 | break; |
| 1155 | path->mnt = &mounted->mnt; |
| 1156 | path->dentry = mounted->mnt.mnt_root; |
| 1157 | nd->flags |= LOOKUP_JUMPED; |
| 1158 | nd->seq = read_seqcount_begin(&path->dentry->d_seq); |
| 1159 | /* |
| 1160 | * Update the inode too. We don't need to re-check the |
| 1161 | * dentry sequence number here after this d_inode read, |
| 1162 | * because a mount-point is always pinned. |
| 1163 | */ |
| 1164 | *inode = path->dentry->d_inode; |
| 1165 | } |
| 1166 | return !read_seqretry(&mount_lock, nd->m_seq) && |
| 1167 | !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT); |
| 1168 | } |
| 1169 | |
| 1170 | static int follow_dotdot_rcu(struct nameidata *nd) |
| 1171 | { |
| 1172 | struct inode *inode = nd->inode; |
| 1173 | if (!nd->root.mnt) |
| 1174 | set_root_rcu(nd); |
| 1175 | |
| 1176 | while (1) { |
| 1177 | if (nd->path.dentry == nd->root.dentry && |
| 1178 | nd->path.mnt == nd->root.mnt) { |
| 1179 | break; |
| 1180 | } |
| 1181 | if (nd->path.dentry != nd->path.mnt->mnt_root) { |
| 1182 | struct dentry *old = nd->path.dentry; |
| 1183 | struct dentry *parent = old->d_parent; |
| 1184 | unsigned seq; |
| 1185 | |
| 1186 | inode = parent->d_inode; |
| 1187 | seq = read_seqcount_begin(&parent->d_seq); |
| 1188 | if (read_seqcount_retry(&old->d_seq, nd->seq)) |
| 1189 | goto failed; |
| 1190 | nd->path.dentry = parent; |
| 1191 | nd->seq = seq; |
| 1192 | break; |
| 1193 | } |
| 1194 | if (!follow_up_rcu(&nd->path)) |
| 1195 | break; |
| 1196 | inode = nd->path.dentry->d_inode; |
| 1197 | nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); |
| 1198 | } |
| 1199 | while (d_mountpoint(nd->path.dentry)) { |
| 1200 | struct mount *mounted; |
| 1201 | mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry); |
| 1202 | if (!mounted) |
| 1203 | break; |
| 1204 | nd->path.mnt = &mounted->mnt; |
| 1205 | nd->path.dentry = mounted->mnt.mnt_root; |
| 1206 | inode = nd->path.dentry->d_inode; |
| 1207 | nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); |
| 1208 | if (read_seqretry(&mount_lock, nd->m_seq)) |
| 1209 | goto failed; |
| 1210 | } |
| 1211 | nd->inode = inode; |
| 1212 | return 0; |
| 1213 | |
| 1214 | failed: |
| 1215 | nd->flags &= ~LOOKUP_RCU; |
| 1216 | if (!(nd->flags & LOOKUP_ROOT)) |
| 1217 | nd->root.mnt = NULL; |
| 1218 | rcu_read_unlock(); |
| 1219 | return -ECHILD; |
| 1220 | } |
| 1221 | |
| 1222 | /* |
| 1223 | * Follow down to the covering mount currently visible to userspace. At each |
| 1224 | * point, the filesystem owning that dentry may be queried as to whether the |
| 1225 | * caller is permitted to proceed or not. |
| 1226 | */ |
| 1227 | int follow_down(struct path *path) |
| 1228 | { |
| 1229 | unsigned managed; |
| 1230 | int ret; |
| 1231 | |
| 1232 | while (managed = ACCESS_ONCE(path->dentry->d_flags), |
| 1233 | unlikely(managed & DCACHE_MANAGED_DENTRY)) { |
| 1234 | /* Allow the filesystem to manage the transit without i_mutex |
| 1235 | * being held. |
| 1236 | * |
| 1237 | * We indicate to the filesystem if someone is trying to mount |
| 1238 | * something here. This gives autofs the chance to deny anyone |
| 1239 | * other than its daemon the right to mount on its |
| 1240 | * superstructure. |
| 1241 | * |
| 1242 | * The filesystem may sleep at this point. |
| 1243 | */ |
| 1244 | if (managed & DCACHE_MANAGE_TRANSIT) { |
| 1245 | BUG_ON(!path->dentry->d_op); |
| 1246 | BUG_ON(!path->dentry->d_op->d_manage); |
| 1247 | ret = path->dentry->d_op->d_manage( |
| 1248 | path->dentry, false); |
| 1249 | if (ret < 0) |
| 1250 | return ret == -EISDIR ? 0 : ret; |
| 1251 | } |
| 1252 | |
| 1253 | /* Transit to a mounted filesystem. */ |
| 1254 | if (managed & DCACHE_MOUNTED) { |
| 1255 | struct vfsmount *mounted = lookup_mnt(path); |
| 1256 | if (!mounted) |
| 1257 | break; |
| 1258 | dput(path->dentry); |
| 1259 | mntput(path->mnt); |
| 1260 | path->mnt = mounted; |
| 1261 | path->dentry = dget(mounted->mnt_root); |
| 1262 | continue; |
| 1263 | } |
| 1264 | |
| 1265 | /* Don't handle automount points here */ |
| 1266 | break; |
| 1267 | } |
| 1268 | return 0; |
| 1269 | } |
| 1270 | EXPORT_SYMBOL(follow_down); |
| 1271 | |
| 1272 | /* |
| 1273 | * Skip to top of mountpoint pile in refwalk mode for follow_dotdot() |
| 1274 | */ |
| 1275 | static void follow_mount(struct path *path) |
| 1276 | { |
| 1277 | while (d_mountpoint(path->dentry)) { |
| 1278 | struct vfsmount *mounted = lookup_mnt(path); |
| 1279 | if (!mounted) |
| 1280 | break; |
| 1281 | dput(path->dentry); |
| 1282 | mntput(path->mnt); |
| 1283 | path->mnt = mounted; |
| 1284 | path->dentry = dget(mounted->mnt_root); |
| 1285 | } |
| 1286 | } |
| 1287 | |
| 1288 | static void follow_dotdot(struct nameidata *nd) |
| 1289 | { |
| 1290 | if (!nd->root.mnt) |
| 1291 | set_root(nd); |
| 1292 | |
| 1293 | while(1) { |
| 1294 | struct dentry *old = nd->path.dentry; |
| 1295 | |
| 1296 | if (nd->path.dentry == nd->root.dentry && |
| 1297 | nd->path.mnt == nd->root.mnt) { |
| 1298 | break; |
| 1299 | } |
| 1300 | if (nd->path.dentry != nd->path.mnt->mnt_root) { |
| 1301 | /* rare case of legitimate dget_parent()... */ |
| 1302 | nd->path.dentry = dget_parent(nd->path.dentry); |
| 1303 | dput(old); |
| 1304 | break; |
| 1305 | } |
| 1306 | if (!follow_up(&nd->path)) |
| 1307 | break; |
| 1308 | } |
| 1309 | follow_mount(&nd->path); |
| 1310 | nd->inode = nd->path.dentry->d_inode; |
| 1311 | } |
| 1312 | |
| 1313 | /* |
| 1314 | * This looks up the name in dcache, possibly revalidates the old dentry and |
| 1315 | * allocates a new one if not found or not valid. In the need_lookup argument |
| 1316 | * returns whether i_op->lookup is necessary. |
| 1317 | * |
| 1318 | * dir->d_inode->i_mutex must be held |
| 1319 | */ |
| 1320 | static struct dentry *lookup_dcache(struct qstr *name, struct dentry *dir, |
| 1321 | unsigned int flags, bool *need_lookup) |
| 1322 | { |
| 1323 | struct dentry *dentry; |
| 1324 | int error; |
| 1325 | |
| 1326 | *need_lookup = false; |
| 1327 | dentry = d_lookup(dir, name); |
| 1328 | if (dentry) { |
| 1329 | if (dentry->d_flags & DCACHE_OP_REVALIDATE) { |
| 1330 | error = d_revalidate(dentry, flags); |
| 1331 | if (unlikely(error <= 0)) { |
| 1332 | if (error < 0) { |
| 1333 | dput(dentry); |
| 1334 | return ERR_PTR(error); |
| 1335 | } else { |
| 1336 | d_invalidate(dentry); |
| 1337 | dput(dentry); |
| 1338 | dentry = NULL; |
| 1339 | } |
| 1340 | } |
| 1341 | } |
| 1342 | } |
| 1343 | |
| 1344 | if (!dentry) { |
| 1345 | dentry = d_alloc(dir, name); |
| 1346 | if (unlikely(!dentry)) |
| 1347 | return ERR_PTR(-ENOMEM); |
| 1348 | |
| 1349 | *need_lookup = true; |
| 1350 | } |
| 1351 | return dentry; |
| 1352 | } |
| 1353 | |
| 1354 | /* |
| 1355 | * Call i_op->lookup on the dentry. The dentry must be negative and |
| 1356 | * unhashed. |
| 1357 | * |
| 1358 | * dir->d_inode->i_mutex must be held |
| 1359 | */ |
| 1360 | static struct dentry *lookup_real(struct inode *dir, struct dentry *dentry, |
| 1361 | unsigned int flags) |
| 1362 | { |
| 1363 | struct dentry *old; |
| 1364 | |
| 1365 | /* Don't create child dentry for a dead directory. */ |
| 1366 | if (unlikely(IS_DEADDIR(dir))) { |
| 1367 | dput(dentry); |
| 1368 | return ERR_PTR(-ENOENT); |
| 1369 | } |
| 1370 | |
| 1371 | old = dir->i_op->lookup(dir, dentry, flags); |
| 1372 | if (unlikely(old)) { |
| 1373 | dput(dentry); |
| 1374 | dentry = old; |
| 1375 | } |
| 1376 | return dentry; |
| 1377 | } |
| 1378 | |
| 1379 | static struct dentry *__lookup_hash(struct qstr *name, |
| 1380 | struct dentry *base, unsigned int flags) |
| 1381 | { |
| 1382 | bool need_lookup; |
| 1383 | struct dentry *dentry; |
| 1384 | |
| 1385 | dentry = lookup_dcache(name, base, flags, &need_lookup); |
| 1386 | if (!need_lookup) |
| 1387 | return dentry; |
| 1388 | |
| 1389 | return lookup_real(base->d_inode, dentry, flags); |
| 1390 | } |
| 1391 | |
| 1392 | /* |
| 1393 | * It's more convoluted than I'd like it to be, but... it's still fairly |
| 1394 | * small and for now I'd prefer to have fast path as straight as possible. |
| 1395 | * It _is_ time-critical. |
| 1396 | */ |
| 1397 | static int lookup_fast(struct nameidata *nd, |
| 1398 | struct path *path, struct inode **inode) |
| 1399 | { |
| 1400 | struct vfsmount *mnt = nd->path.mnt; |
| 1401 | struct dentry *dentry, *parent = nd->path.dentry; |
| 1402 | int need_reval = 1; |
| 1403 | int status = 1; |
| 1404 | int err; |
| 1405 | |
| 1406 | /* |
| 1407 | * Rename seqlock is not required here because in the off chance |
| 1408 | * of a false negative due to a concurrent rename, we're going to |
| 1409 | * do the non-racy lookup, below. |
| 1410 | */ |
| 1411 | if (nd->flags & LOOKUP_RCU) { |
| 1412 | unsigned seq; |
| 1413 | dentry = __d_lookup_rcu(parent, &nd->last, &seq); |
| 1414 | if (!dentry) |
| 1415 | goto unlazy; |
| 1416 | |
| 1417 | /* |
| 1418 | * This sequence count validates that the inode matches |
| 1419 | * the dentry name information from lookup. |
| 1420 | */ |
| 1421 | *inode = dentry->d_inode; |
| 1422 | if (read_seqcount_retry(&dentry->d_seq, seq)) |
| 1423 | return -ECHILD; |
| 1424 | |
| 1425 | /* |
| 1426 | * This sequence count validates that the parent had no |
| 1427 | * changes while we did the lookup of the dentry above. |
| 1428 | * |
| 1429 | * The memory barrier in read_seqcount_begin of child is |
| 1430 | * enough, we can use __read_seqcount_retry here. |
| 1431 | */ |
| 1432 | if (__read_seqcount_retry(&parent->d_seq, nd->seq)) |
| 1433 | return -ECHILD; |
| 1434 | nd->seq = seq; |
| 1435 | |
| 1436 | if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) { |
| 1437 | status = d_revalidate(dentry, nd->flags); |
| 1438 | if (unlikely(status <= 0)) { |
| 1439 | if (status != -ECHILD) |
| 1440 | need_reval = 0; |
| 1441 | goto unlazy; |
| 1442 | } |
| 1443 | } |
| 1444 | path->mnt = mnt; |
| 1445 | path->dentry = dentry; |
| 1446 | if (likely(__follow_mount_rcu(nd, path, inode))) |
| 1447 | return 0; |
| 1448 | unlazy: |
| 1449 | if (unlazy_walk(nd, dentry)) |
| 1450 | return -ECHILD; |
| 1451 | } else { |
| 1452 | dentry = __d_lookup(parent, &nd->last); |
| 1453 | } |
| 1454 | |
| 1455 | if (unlikely(!dentry)) |
| 1456 | goto need_lookup; |
| 1457 | |
| 1458 | if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE) && need_reval) |
| 1459 | status = d_revalidate(dentry, nd->flags); |
| 1460 | if (unlikely(status <= 0)) { |
| 1461 | if (status < 0) { |
| 1462 | dput(dentry); |
| 1463 | return status; |
| 1464 | } |
| 1465 | d_invalidate(dentry); |
| 1466 | dput(dentry); |
| 1467 | goto need_lookup; |
| 1468 | } |
| 1469 | |
| 1470 | path->mnt = mnt; |
| 1471 | path->dentry = dentry; |
| 1472 | err = follow_managed(path, nd->flags); |
| 1473 | if (unlikely(err < 0)) { |
| 1474 | path_put_conditional(path, nd); |
| 1475 | return err; |
| 1476 | } |
| 1477 | if (err) |
| 1478 | nd->flags |= LOOKUP_JUMPED; |
| 1479 | *inode = path->dentry->d_inode; |
| 1480 | return 0; |
| 1481 | |
| 1482 | need_lookup: |
| 1483 | return 1; |
| 1484 | } |
| 1485 | |
| 1486 | /* Fast lookup failed, do it the slow way */ |
| 1487 | static int lookup_slow(struct nameidata *nd, struct path *path) |
| 1488 | { |
| 1489 | struct dentry *dentry, *parent; |
| 1490 | int err; |
| 1491 | |
| 1492 | parent = nd->path.dentry; |
| 1493 | BUG_ON(nd->inode != parent->d_inode); |
| 1494 | |
| 1495 | mutex_lock(&parent->d_inode->i_mutex); |
| 1496 | dentry = __lookup_hash(&nd->last, parent, nd->flags); |
| 1497 | mutex_unlock(&parent->d_inode->i_mutex); |
| 1498 | if (IS_ERR(dentry)) |
| 1499 | return PTR_ERR(dentry); |
| 1500 | path->mnt = nd->path.mnt; |
| 1501 | path->dentry = dentry; |
| 1502 | err = follow_managed(path, nd->flags); |
| 1503 | if (unlikely(err < 0)) { |
| 1504 | path_put_conditional(path, nd); |
| 1505 | return err; |
| 1506 | } |
| 1507 | if (err) |
| 1508 | nd->flags |= LOOKUP_JUMPED; |
| 1509 | return 0; |
| 1510 | } |
| 1511 | |
| 1512 | static inline int may_lookup(struct nameidata *nd) |
| 1513 | { |
| 1514 | if (nd->flags & LOOKUP_RCU) { |
| 1515 | int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK); |
| 1516 | if (err != -ECHILD) |
| 1517 | return err; |
| 1518 | if (unlazy_walk(nd, NULL)) |
| 1519 | return -ECHILD; |
| 1520 | } |
| 1521 | return inode_permission(nd->inode, MAY_EXEC); |
| 1522 | } |
| 1523 | |
| 1524 | static inline int handle_dots(struct nameidata *nd, int type) |
| 1525 | { |
| 1526 | if (type == LAST_DOTDOT) { |
| 1527 | if (nd->flags & LOOKUP_RCU) { |
| 1528 | if (follow_dotdot_rcu(nd)) |
| 1529 | return -ECHILD; |
| 1530 | } else |
| 1531 | follow_dotdot(nd); |
| 1532 | } |
| 1533 | return 0; |
| 1534 | } |
| 1535 | |
| 1536 | static void terminate_walk(struct nameidata *nd) |
| 1537 | { |
| 1538 | if (!(nd->flags & LOOKUP_RCU)) { |
| 1539 | path_put(&nd->path); |
| 1540 | } else { |
| 1541 | nd->flags &= ~LOOKUP_RCU; |
| 1542 | if (!(nd->flags & LOOKUP_ROOT)) |
| 1543 | nd->root.mnt = NULL; |
| 1544 | rcu_read_unlock(); |
| 1545 | } |
| 1546 | } |
| 1547 | |
| 1548 | /* |
| 1549 | * Do we need to follow links? We _really_ want to be able |
| 1550 | * to do this check without having to look at inode->i_op, |
| 1551 | * so we keep a cache of "no, this doesn't need follow_link" |
| 1552 | * for the common case. |
| 1553 | */ |
| 1554 | static inline int should_follow_link(struct dentry *dentry, int follow) |
| 1555 | { |
| 1556 | return unlikely(d_is_symlink(dentry)) ? follow : 0; |
| 1557 | } |
| 1558 | |
| 1559 | static inline int walk_component(struct nameidata *nd, struct path *path, |
| 1560 | int follow) |
| 1561 | { |
| 1562 | struct inode *inode; |
| 1563 | int err; |
| 1564 | /* |
| 1565 | * "." and ".." are special - ".." especially so because it has |
| 1566 | * to be able to know about the current root directory and |
| 1567 | * parent relationships. |
| 1568 | */ |
| 1569 | if (unlikely(nd->last_type != LAST_NORM)) |
| 1570 | return handle_dots(nd, nd->last_type); |
| 1571 | err = lookup_fast(nd, path, &inode); |
| 1572 | if (unlikely(err)) { |
| 1573 | if (err < 0) |
| 1574 | goto out_err; |
| 1575 | |
| 1576 | err = lookup_slow(nd, path); |
| 1577 | if (err < 0) |
| 1578 | goto out_err; |
| 1579 | |
| 1580 | inode = path->dentry->d_inode; |
| 1581 | } |
| 1582 | err = -ENOENT; |
| 1583 | if (!inode || d_is_negative(path->dentry)) |
| 1584 | goto out_path_put; |
| 1585 | |
| 1586 | if (should_follow_link(path->dentry, follow)) { |
| 1587 | if (nd->flags & LOOKUP_RCU) { |
| 1588 | if (unlikely(unlazy_walk(nd, path->dentry))) { |
| 1589 | err = -ECHILD; |
| 1590 | goto out_err; |
| 1591 | } |
| 1592 | } |
| 1593 | BUG_ON(inode != path->dentry->d_inode); |
| 1594 | return 1; |
| 1595 | } |
| 1596 | path_to_nameidata(path, nd); |
| 1597 | nd->inode = inode; |
| 1598 | return 0; |
| 1599 | |
| 1600 | out_path_put: |
| 1601 | path_to_nameidata(path, nd); |
| 1602 | out_err: |
| 1603 | terminate_walk(nd); |
| 1604 | return err; |
| 1605 | } |
| 1606 | |
| 1607 | /* |
| 1608 | * This limits recursive symlink follows to 8, while |
| 1609 | * limiting consecutive symlinks to 40. |
| 1610 | * |
| 1611 | * Without that kind of total limit, nasty chains of consecutive |
| 1612 | * symlinks can cause almost arbitrarily long lookups. |
| 1613 | */ |
| 1614 | static inline int nested_symlink(struct path *path, struct nameidata *nd) |
| 1615 | { |
| 1616 | int res; |
| 1617 | |
| 1618 | if (unlikely(current->link_count >= MAX_NESTED_LINKS)) { |
| 1619 | path_put_conditional(path, nd); |
| 1620 | path_put(&nd->path); |
| 1621 | return -ELOOP; |
| 1622 | } |
| 1623 | BUG_ON(nd->depth >= MAX_NESTED_LINKS); |
| 1624 | |
| 1625 | nd->depth++; |
| 1626 | current->link_count++; |
| 1627 | |
| 1628 | do { |
| 1629 | struct path link = *path; |
| 1630 | void *cookie; |
| 1631 | |
| 1632 | res = follow_link(&link, nd, &cookie); |
| 1633 | if (res) |
| 1634 | break; |
| 1635 | res = walk_component(nd, path, LOOKUP_FOLLOW); |
| 1636 | put_link(nd, &link, cookie); |
| 1637 | } while (res > 0); |
| 1638 | |
| 1639 | current->link_count--; |
| 1640 | nd->depth--; |
| 1641 | return res; |
| 1642 | } |
| 1643 | |
| 1644 | /* |
| 1645 | * We can do the critical dentry name comparison and hashing |
| 1646 | * operations one word at a time, but we are limited to: |
| 1647 | * |
| 1648 | * - Architectures with fast unaligned word accesses. We could |
| 1649 | * do a "get_unaligned()" if this helps and is sufficiently |
| 1650 | * fast. |
| 1651 | * |
| 1652 | * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we |
| 1653 | * do not trap on the (extremely unlikely) case of a page |
| 1654 | * crossing operation. |
| 1655 | * |
| 1656 | * - Furthermore, we need an efficient 64-bit compile for the |
| 1657 | * 64-bit case in order to generate the "number of bytes in |
| 1658 | * the final mask". Again, that could be replaced with a |
| 1659 | * efficient population count instruction or similar. |
| 1660 | */ |
| 1661 | #ifdef CONFIG_DCACHE_WORD_ACCESS |
| 1662 | |
| 1663 | #include <asm/word-at-a-time.h> |
| 1664 | |
| 1665 | #ifdef CONFIG_64BIT |
| 1666 | |
| 1667 | static inline unsigned int fold_hash(unsigned long hash) |
| 1668 | { |
| 1669 | return hash_64(hash, 32); |
| 1670 | } |
| 1671 | |
| 1672 | #else /* 32-bit case */ |
| 1673 | |
| 1674 | #define fold_hash(x) (x) |
| 1675 | |
| 1676 | #endif |
| 1677 | |
| 1678 | unsigned int full_name_hash(const unsigned char *name, unsigned int len) |
| 1679 | { |
| 1680 | unsigned long a, mask; |
| 1681 | unsigned long hash = 0; |
| 1682 | |
| 1683 | for (;;) { |
| 1684 | a = load_unaligned_zeropad(name); |
| 1685 | if (len < sizeof(unsigned long)) |
| 1686 | break; |
| 1687 | hash += a; |
| 1688 | hash *= 9; |
| 1689 | name += sizeof(unsigned long); |
| 1690 | len -= sizeof(unsigned long); |
| 1691 | if (!len) |
| 1692 | goto done; |
| 1693 | } |
| 1694 | mask = bytemask_from_count(len); |
| 1695 | hash += mask & a; |
| 1696 | done: |
| 1697 | return fold_hash(hash); |
| 1698 | } |
| 1699 | EXPORT_SYMBOL(full_name_hash); |
| 1700 | |
| 1701 | /* |
| 1702 | * Calculate the length and hash of the path component, and |
| 1703 | * return the "hash_len" as the result. |
| 1704 | */ |
| 1705 | static inline u64 hash_name(const char *name) |
| 1706 | { |
| 1707 | unsigned long a, b, adata, bdata, mask, hash, len; |
| 1708 | const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS; |
| 1709 | |
| 1710 | hash = a = 0; |
| 1711 | len = -sizeof(unsigned long); |
| 1712 | do { |
| 1713 | hash = (hash + a) * 9; |
| 1714 | len += sizeof(unsigned long); |
| 1715 | a = load_unaligned_zeropad(name+len); |
| 1716 | b = a ^ REPEAT_BYTE('/'); |
| 1717 | } while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants))); |
| 1718 | |
| 1719 | adata = prep_zero_mask(a, adata, &constants); |
| 1720 | bdata = prep_zero_mask(b, bdata, &constants); |
| 1721 | |
| 1722 | mask = create_zero_mask(adata | bdata); |
| 1723 | |
| 1724 | hash += a & zero_bytemask(mask); |
| 1725 | len += find_zero(mask); |
| 1726 | return hashlen_create(fold_hash(hash), len); |
| 1727 | } |
| 1728 | |
| 1729 | #else |
| 1730 | |
| 1731 | unsigned int full_name_hash(const unsigned char *name, unsigned int len) |
| 1732 | { |
| 1733 | unsigned long hash = init_name_hash(); |
| 1734 | while (len--) |
| 1735 | hash = partial_name_hash(*name++, hash); |
| 1736 | return end_name_hash(hash); |
| 1737 | } |
| 1738 | EXPORT_SYMBOL(full_name_hash); |
| 1739 | |
| 1740 | /* |
| 1741 | * We know there's a real path component here of at least |
| 1742 | * one character. |
| 1743 | */ |
| 1744 | static inline u64 hash_name(const char *name) |
| 1745 | { |
| 1746 | unsigned long hash = init_name_hash(); |
| 1747 | unsigned long len = 0, c; |
| 1748 | |
| 1749 | c = (unsigned char)*name; |
| 1750 | do { |
| 1751 | len++; |
| 1752 | hash = partial_name_hash(c, hash); |
| 1753 | c = (unsigned char)name[len]; |
| 1754 | } while (c && c != '/'); |
| 1755 | return hashlen_create(end_name_hash(hash), len); |
| 1756 | } |
| 1757 | |
| 1758 | #endif |
| 1759 | |
| 1760 | /* |
| 1761 | * Name resolution. |
| 1762 | * This is the basic name resolution function, turning a pathname into |
| 1763 | * the final dentry. We expect 'base' to be positive and a directory. |
| 1764 | * |
| 1765 | * Returns 0 and nd will have valid dentry and mnt on success. |
| 1766 | * Returns error and drops reference to input namei data on failure. |
| 1767 | */ |
| 1768 | static int link_path_walk(const char *name, struct nameidata *nd) |
| 1769 | { |
| 1770 | struct path next; |
| 1771 | int err; |
| 1772 | |
| 1773 | while (*name=='/') |
| 1774 | name++; |
| 1775 | if (!*name) |
| 1776 | return 0; |
| 1777 | |
| 1778 | /* At this point we know we have a real path component. */ |
| 1779 | for(;;) { |
| 1780 | u64 hash_len; |
| 1781 | int type; |
| 1782 | |
| 1783 | err = may_lookup(nd); |
| 1784 | if (err) |
| 1785 | break; |
| 1786 | |
| 1787 | hash_len = hash_name(name); |
| 1788 | |
| 1789 | type = LAST_NORM; |
| 1790 | if (name[0] == '.') switch (hashlen_len(hash_len)) { |
| 1791 | case 2: |
| 1792 | if (name[1] == '.') { |
| 1793 | type = LAST_DOTDOT; |
| 1794 | nd->flags |= LOOKUP_JUMPED; |
| 1795 | } |
| 1796 | break; |
| 1797 | case 1: |
| 1798 | type = LAST_DOT; |
| 1799 | } |
| 1800 | if (likely(type == LAST_NORM)) { |
| 1801 | struct dentry *parent = nd->path.dentry; |
| 1802 | nd->flags &= ~LOOKUP_JUMPED; |
| 1803 | if (unlikely(parent->d_flags & DCACHE_OP_HASH)) { |
| 1804 | struct qstr this = { { .hash_len = hash_len }, .name = name }; |
| 1805 | err = parent->d_op->d_hash(parent, &this); |
| 1806 | if (err < 0) |
| 1807 | break; |
| 1808 | hash_len = this.hash_len; |
| 1809 | name = this.name; |
| 1810 | } |
| 1811 | } |
| 1812 | |
| 1813 | nd->last.hash_len = hash_len; |
| 1814 | nd->last.name = name; |
| 1815 | nd->last_type = type; |
| 1816 | |
| 1817 | name += hashlen_len(hash_len); |
| 1818 | if (!*name) |
| 1819 | return 0; |
| 1820 | /* |
| 1821 | * If it wasn't NUL, we know it was '/'. Skip that |
| 1822 | * slash, and continue until no more slashes. |
| 1823 | */ |
| 1824 | do { |
| 1825 | name++; |
| 1826 | } while (unlikely(*name == '/')); |
| 1827 | if (!*name) |
| 1828 | return 0; |
| 1829 | |
| 1830 | err = walk_component(nd, &next, LOOKUP_FOLLOW); |
| 1831 | if (err < 0) |
| 1832 | return err; |
| 1833 | |
| 1834 | if (err) { |
| 1835 | err = nested_symlink(&next, nd); |
| 1836 | if (err) |
| 1837 | return err; |
| 1838 | } |
| 1839 | if (!d_can_lookup(nd->path.dentry)) { |
| 1840 | err = -ENOTDIR; |
| 1841 | break; |
| 1842 | } |
| 1843 | } |
| 1844 | terminate_walk(nd); |
| 1845 | return err; |
| 1846 | } |
| 1847 | |
| 1848 | static int path_init(int dfd, const char *name, unsigned int flags, |
| 1849 | struct nameidata *nd) |
| 1850 | { |
| 1851 | int retval = 0; |
| 1852 | |
| 1853 | nd->last_type = LAST_ROOT; /* if there are only slashes... */ |
| 1854 | nd->flags = flags | LOOKUP_JUMPED | LOOKUP_PARENT; |
| 1855 | nd->depth = 0; |
| 1856 | nd->base = NULL; |
| 1857 | if (flags & LOOKUP_ROOT) { |
| 1858 | struct dentry *root = nd->root.dentry; |
| 1859 | struct inode *inode = root->d_inode; |
| 1860 | if (*name) { |
| 1861 | if (!d_can_lookup(root)) |
| 1862 | return -ENOTDIR; |
| 1863 | retval = inode_permission(inode, MAY_EXEC); |
| 1864 | if (retval) |
| 1865 | return retval; |
| 1866 | } |
| 1867 | nd->path = nd->root; |
| 1868 | nd->inode = inode; |
| 1869 | if (flags & LOOKUP_RCU) { |
| 1870 | rcu_read_lock(); |
| 1871 | nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); |
| 1872 | nd->m_seq = read_seqbegin(&mount_lock); |
| 1873 | } else { |
| 1874 | path_get(&nd->path); |
| 1875 | } |
| 1876 | goto done; |
| 1877 | } |
| 1878 | |
| 1879 | nd->root.mnt = NULL; |
| 1880 | |
| 1881 | nd->m_seq = read_seqbegin(&mount_lock); |
| 1882 | if (*name=='/') { |
| 1883 | if (flags & LOOKUP_RCU) { |
| 1884 | rcu_read_lock(); |
| 1885 | nd->seq = set_root_rcu(nd); |
| 1886 | } else { |
| 1887 | set_root(nd); |
| 1888 | path_get(&nd->root); |
| 1889 | } |
| 1890 | nd->path = nd->root; |
| 1891 | } else if (dfd == AT_FDCWD) { |
| 1892 | if (flags & LOOKUP_RCU) { |
| 1893 | struct fs_struct *fs = current->fs; |
| 1894 | unsigned seq; |
| 1895 | |
| 1896 | rcu_read_lock(); |
| 1897 | |
| 1898 | do { |
| 1899 | seq = read_seqcount_begin(&fs->seq); |
| 1900 | nd->path = fs->pwd; |
| 1901 | nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); |
| 1902 | } while (read_seqcount_retry(&fs->seq, seq)); |
| 1903 | } else { |
| 1904 | get_fs_pwd(current->fs, &nd->path); |
| 1905 | } |
| 1906 | } else { |
| 1907 | /* Caller must check execute permissions on the starting path component */ |
| 1908 | struct fd f = fdget_raw(dfd); |
| 1909 | struct dentry *dentry; |
| 1910 | |
| 1911 | if (!f.file) |
| 1912 | return -EBADF; |
| 1913 | |
| 1914 | dentry = f.file->f_path.dentry; |
| 1915 | |
| 1916 | if (*name) { |
| 1917 | if (!d_can_lookup(dentry)) { |
| 1918 | fdput(f); |
| 1919 | return -ENOTDIR; |
| 1920 | } |
| 1921 | } |
| 1922 | |
| 1923 | nd->path = f.file->f_path; |
| 1924 | if (flags & LOOKUP_RCU) { |
| 1925 | if (f.flags & FDPUT_FPUT) |
| 1926 | nd->base = f.file; |
| 1927 | nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); |
| 1928 | rcu_read_lock(); |
| 1929 | } else { |
| 1930 | path_get(&nd->path); |
| 1931 | fdput(f); |
| 1932 | } |
| 1933 | } |
| 1934 | |
| 1935 | nd->inode = nd->path.dentry->d_inode; |
| 1936 | if (!(flags & LOOKUP_RCU)) |
| 1937 | goto done; |
| 1938 | if (likely(!read_seqcount_retry(&nd->path.dentry->d_seq, nd->seq))) |
| 1939 | goto done; |
| 1940 | if (!(nd->flags & LOOKUP_ROOT)) |
| 1941 | nd->root.mnt = NULL; |
| 1942 | rcu_read_unlock(); |
| 1943 | return -ECHILD; |
| 1944 | done: |
| 1945 | current->total_link_count = 0; |
| 1946 | return link_path_walk(name, nd); |
| 1947 | } |
| 1948 | |
| 1949 | static void path_cleanup(struct nameidata *nd) |
| 1950 | { |
| 1951 | if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) { |
| 1952 | path_put(&nd->root); |
| 1953 | nd->root.mnt = NULL; |
| 1954 | } |
| 1955 | if (unlikely(nd->base)) |
| 1956 | fput(nd->base); |
| 1957 | } |
| 1958 | |
| 1959 | static inline int lookup_last(struct nameidata *nd, struct path *path) |
| 1960 | { |
| 1961 | if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len]) |
| 1962 | nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; |
| 1963 | |
| 1964 | nd->flags &= ~LOOKUP_PARENT; |
| 1965 | return walk_component(nd, path, nd->flags & LOOKUP_FOLLOW); |
| 1966 | } |
| 1967 | |
| 1968 | /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */ |
| 1969 | static int path_lookupat(int dfd, const char *name, |
| 1970 | unsigned int flags, struct nameidata *nd) |
| 1971 | { |
| 1972 | struct path path; |
| 1973 | int err; |
| 1974 | |
| 1975 | /* |
| 1976 | * Path walking is largely split up into 2 different synchronisation |
| 1977 | * schemes, rcu-walk and ref-walk (explained in |
| 1978 | * Documentation/filesystems/path-lookup.txt). These share much of the |
| 1979 | * path walk code, but some things particularly setup, cleanup, and |
| 1980 | * following mounts are sufficiently divergent that functions are |
| 1981 | * duplicated. Typically there is a function foo(), and its RCU |
| 1982 | * analogue, foo_rcu(). |
| 1983 | * |
| 1984 | * -ECHILD is the error number of choice (just to avoid clashes) that |
| 1985 | * is returned if some aspect of an rcu-walk fails. Such an error must |
| 1986 | * be handled by restarting a traditional ref-walk (which will always |
| 1987 | * be able to complete). |
| 1988 | */ |
| 1989 | err = path_init(dfd, name, flags, nd); |
| 1990 | if (!err && !(flags & LOOKUP_PARENT)) { |
| 1991 | err = lookup_last(nd, &path); |
| 1992 | while (err > 0) { |
| 1993 | void *cookie; |
| 1994 | struct path link = path; |
| 1995 | err = may_follow_link(&link, nd); |
| 1996 | if (unlikely(err)) |
| 1997 | break; |
| 1998 | nd->flags |= LOOKUP_PARENT; |
| 1999 | err = follow_link(&link, nd, &cookie); |
| 2000 | if (err) |
| 2001 | break; |
| 2002 | err = lookup_last(nd, &path); |
| 2003 | put_link(nd, &link, cookie); |
| 2004 | } |
| 2005 | } |
| 2006 | |
| 2007 | if (!err) |
| 2008 | err = complete_walk(nd); |
| 2009 | |
| 2010 | if (!err && nd->flags & LOOKUP_DIRECTORY) { |
| 2011 | if (!d_can_lookup(nd->path.dentry)) { |
| 2012 | path_put(&nd->path); |
| 2013 | err = -ENOTDIR; |
| 2014 | } |
| 2015 | } |
| 2016 | |
| 2017 | path_cleanup(nd); |
| 2018 | return err; |
| 2019 | } |
| 2020 | |
| 2021 | static int filename_lookup(int dfd, struct filename *name, |
| 2022 | unsigned int flags, struct nameidata *nd) |
| 2023 | { |
| 2024 | int retval = path_lookupat(dfd, name->name, flags | LOOKUP_RCU, nd); |
| 2025 | if (unlikely(retval == -ECHILD)) |
| 2026 | retval = path_lookupat(dfd, name->name, flags, nd); |
| 2027 | if (unlikely(retval == -ESTALE)) |
| 2028 | retval = path_lookupat(dfd, name->name, |
| 2029 | flags | LOOKUP_REVAL, nd); |
| 2030 | |
| 2031 | if (likely(!retval)) |
| 2032 | audit_inode(name, nd->path.dentry, flags & LOOKUP_PARENT); |
| 2033 | return retval; |
| 2034 | } |
| 2035 | |
| 2036 | static int do_path_lookup(int dfd, const char *name, |
| 2037 | unsigned int flags, struct nameidata *nd) |
| 2038 | { |
| 2039 | struct filename filename = { .name = name }; |
| 2040 | |
| 2041 | return filename_lookup(dfd, &filename, flags, nd); |
| 2042 | } |
| 2043 | |
| 2044 | /* does lookup, returns the object with parent locked */ |
| 2045 | struct dentry *kern_path_locked(const char *name, struct path *path) |
| 2046 | { |
| 2047 | struct nameidata nd; |
| 2048 | struct dentry *d; |
| 2049 | int err = do_path_lookup(AT_FDCWD, name, LOOKUP_PARENT, &nd); |
| 2050 | if (err) |
| 2051 | return ERR_PTR(err); |
| 2052 | if (nd.last_type != LAST_NORM) { |
| 2053 | path_put(&nd.path); |
| 2054 | return ERR_PTR(-EINVAL); |
| 2055 | } |
| 2056 | mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); |
| 2057 | d = __lookup_hash(&nd.last, nd.path.dentry, 0); |
| 2058 | if (IS_ERR(d)) { |
| 2059 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); |
| 2060 | path_put(&nd.path); |
| 2061 | return d; |
| 2062 | } |
| 2063 | *path = nd.path; |
| 2064 | return d; |
| 2065 | } |
| 2066 | |
| 2067 | int kern_path(const char *name, unsigned int flags, struct path *path) |
| 2068 | { |
| 2069 | struct nameidata nd; |
| 2070 | int res = do_path_lookup(AT_FDCWD, name, flags, &nd); |
| 2071 | if (!res) |
| 2072 | *path = nd.path; |
| 2073 | return res; |
| 2074 | } |
| 2075 | EXPORT_SYMBOL(kern_path); |
| 2076 | |
| 2077 | /** |
| 2078 | * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair |
| 2079 | * @dentry: pointer to dentry of the base directory |
| 2080 | * @mnt: pointer to vfs mount of the base directory |
| 2081 | * @name: pointer to file name |
| 2082 | * @flags: lookup flags |
| 2083 | * @path: pointer to struct path to fill |
| 2084 | */ |
| 2085 | int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt, |
| 2086 | const char *name, unsigned int flags, |
| 2087 | struct path *path) |
| 2088 | { |
| 2089 | struct nameidata nd; |
| 2090 | int err; |
| 2091 | nd.root.dentry = dentry; |
| 2092 | nd.root.mnt = mnt; |
| 2093 | BUG_ON(flags & LOOKUP_PARENT); |
| 2094 | /* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */ |
| 2095 | err = do_path_lookup(AT_FDCWD, name, flags | LOOKUP_ROOT, &nd); |
| 2096 | if (!err) |
| 2097 | *path = nd.path; |
| 2098 | return err; |
| 2099 | } |
| 2100 | EXPORT_SYMBOL(vfs_path_lookup); |
| 2101 | |
| 2102 | /* |
| 2103 | * Restricted form of lookup. Doesn't follow links, single-component only, |
| 2104 | * needs parent already locked. Doesn't follow mounts. |
| 2105 | * SMP-safe. |
| 2106 | */ |
| 2107 | static struct dentry *lookup_hash(struct nameidata *nd) |
| 2108 | { |
| 2109 | return __lookup_hash(&nd->last, nd->path.dentry, nd->flags); |
| 2110 | } |
| 2111 | |
| 2112 | /** |
| 2113 | * lookup_one_len - filesystem helper to lookup single pathname component |
| 2114 | * @name: pathname component to lookup |
| 2115 | * @base: base directory to lookup from |
| 2116 | * @len: maximum length @len should be interpreted to |
| 2117 | * |
| 2118 | * Note that this routine is purely a helper for filesystem usage and should |
| 2119 | * not be called by generic code. Also note that by using this function the |
| 2120 | * nameidata argument is passed to the filesystem methods and a filesystem |
| 2121 | * using this helper needs to be prepared for that. |
| 2122 | */ |
| 2123 | struct dentry *lookup_one_len(const char *name, struct dentry *base, int len) |
| 2124 | { |
| 2125 | struct qstr this; |
| 2126 | unsigned int c; |
| 2127 | int err; |
| 2128 | |
| 2129 | WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex)); |
| 2130 | |
| 2131 | this.name = name; |
| 2132 | this.len = len; |
| 2133 | this.hash = full_name_hash(name, len); |
| 2134 | if (!len) |
| 2135 | return ERR_PTR(-EACCES); |
| 2136 | |
| 2137 | if (unlikely(name[0] == '.')) { |
| 2138 | if (len < 2 || (len == 2 && name[1] == '.')) |
| 2139 | return ERR_PTR(-EACCES); |
| 2140 | } |
| 2141 | |
| 2142 | while (len--) { |
| 2143 | c = *(const unsigned char *)name++; |
| 2144 | if (c == '/' || c == '\0') |
| 2145 | return ERR_PTR(-EACCES); |
| 2146 | } |
| 2147 | /* |
| 2148 | * See if the low-level filesystem might want |
| 2149 | * to use its own hash.. |
| 2150 | */ |
| 2151 | if (base->d_flags & DCACHE_OP_HASH) { |
| 2152 | int err = base->d_op->d_hash(base, &this); |
| 2153 | if (err < 0) |
| 2154 | return ERR_PTR(err); |
| 2155 | } |
| 2156 | |
| 2157 | err = inode_permission(base->d_inode, MAY_EXEC); |
| 2158 | if (err) |
| 2159 | return ERR_PTR(err); |
| 2160 | |
| 2161 | return __lookup_hash(&this, base, 0); |
| 2162 | } |
| 2163 | EXPORT_SYMBOL(lookup_one_len); |
| 2164 | |
| 2165 | int user_path_at_empty(int dfd, const char __user *name, unsigned flags, |
| 2166 | struct path *path, int *empty) |
| 2167 | { |
| 2168 | struct nameidata nd; |
| 2169 | struct filename *tmp = getname_flags(name, flags, empty); |
| 2170 | int err = PTR_ERR(tmp); |
| 2171 | if (!IS_ERR(tmp)) { |
| 2172 | |
| 2173 | BUG_ON(flags & LOOKUP_PARENT); |
| 2174 | |
| 2175 | err = filename_lookup(dfd, tmp, flags, &nd); |
| 2176 | putname(tmp); |
| 2177 | if (!err) |
| 2178 | *path = nd.path; |
| 2179 | } |
| 2180 | return err; |
| 2181 | } |
| 2182 | |
| 2183 | int user_path_at(int dfd, const char __user *name, unsigned flags, |
| 2184 | struct path *path) |
| 2185 | { |
| 2186 | return user_path_at_empty(dfd, name, flags, path, NULL); |
| 2187 | } |
| 2188 | EXPORT_SYMBOL(user_path_at); |
| 2189 | |
| 2190 | /* |
| 2191 | * NB: most callers don't do anything directly with the reference to the |
| 2192 | * to struct filename, but the nd->last pointer points into the name string |
| 2193 | * allocated by getname. So we must hold the reference to it until all |
| 2194 | * path-walking is complete. |
| 2195 | */ |
| 2196 | static struct filename * |
| 2197 | user_path_parent(int dfd, const char __user *path, struct nameidata *nd, |
| 2198 | unsigned int flags) |
| 2199 | { |
| 2200 | struct filename *s = getname(path); |
| 2201 | int error; |
| 2202 | |
| 2203 | /* only LOOKUP_REVAL is allowed in extra flags */ |
| 2204 | flags &= LOOKUP_REVAL; |
| 2205 | |
| 2206 | if (IS_ERR(s)) |
| 2207 | return s; |
| 2208 | |
| 2209 | error = filename_lookup(dfd, s, flags | LOOKUP_PARENT, nd); |
| 2210 | if (error) { |
| 2211 | putname(s); |
| 2212 | return ERR_PTR(error); |
| 2213 | } |
| 2214 | |
| 2215 | return s; |
| 2216 | } |
| 2217 | |
| 2218 | /** |
| 2219 | * mountpoint_last - look up last component for umount |
| 2220 | * @nd: pathwalk nameidata - currently pointing at parent directory of "last" |
| 2221 | * @path: pointer to container for result |
| 2222 | * |
| 2223 | * This is a special lookup_last function just for umount. In this case, we |
| 2224 | * need to resolve the path without doing any revalidation. |
| 2225 | * |
| 2226 | * The nameidata should be the result of doing a LOOKUP_PARENT pathwalk. Since |
| 2227 | * mountpoints are always pinned in the dcache, their ancestors are too. Thus, |
| 2228 | * in almost all cases, this lookup will be served out of the dcache. The only |
| 2229 | * cases where it won't are if nd->last refers to a symlink or the path is |
| 2230 | * bogus and it doesn't exist. |
| 2231 | * |
| 2232 | * Returns: |
| 2233 | * -error: if there was an error during lookup. This includes -ENOENT if the |
| 2234 | * lookup found a negative dentry. The nd->path reference will also be |
| 2235 | * put in this case. |
| 2236 | * |
| 2237 | * 0: if we successfully resolved nd->path and found it to not to be a |
| 2238 | * symlink that needs to be followed. "path" will also be populated. |
| 2239 | * The nd->path reference will also be put. |
| 2240 | * |
| 2241 | * 1: if we successfully resolved nd->last and found it to be a symlink |
| 2242 | * that needs to be followed. "path" will be populated with the path |
| 2243 | * to the link, and nd->path will *not* be put. |
| 2244 | */ |
| 2245 | static int |
| 2246 | mountpoint_last(struct nameidata *nd, struct path *path) |
| 2247 | { |
| 2248 | int error = 0; |
| 2249 | struct dentry *dentry; |
| 2250 | struct dentry *dir = nd->path.dentry; |
| 2251 | |
| 2252 | /* If we're in rcuwalk, drop out of it to handle last component */ |
| 2253 | if (nd->flags & LOOKUP_RCU) { |
| 2254 | if (unlazy_walk(nd, NULL)) { |
| 2255 | error = -ECHILD; |
| 2256 | goto out; |
| 2257 | } |
| 2258 | } |
| 2259 | |
| 2260 | nd->flags &= ~LOOKUP_PARENT; |
| 2261 | |
| 2262 | if (unlikely(nd->last_type != LAST_NORM)) { |
| 2263 | error = handle_dots(nd, nd->last_type); |
| 2264 | if (error) |
| 2265 | goto out; |
| 2266 | dentry = dget(nd->path.dentry); |
| 2267 | goto done; |
| 2268 | } |
| 2269 | |
| 2270 | mutex_lock(&dir->d_inode->i_mutex); |
| 2271 | dentry = d_lookup(dir, &nd->last); |
| 2272 | if (!dentry) { |
| 2273 | /* |
| 2274 | * No cached dentry. Mounted dentries are pinned in the cache, |
| 2275 | * so that means that this dentry is probably a symlink or the |
| 2276 | * path doesn't actually point to a mounted dentry. |
| 2277 | */ |
| 2278 | dentry = d_alloc(dir, &nd->last); |
| 2279 | if (!dentry) { |
| 2280 | error = -ENOMEM; |
| 2281 | mutex_unlock(&dir->d_inode->i_mutex); |
| 2282 | goto out; |
| 2283 | } |
| 2284 | dentry = lookup_real(dir->d_inode, dentry, nd->flags); |
| 2285 | error = PTR_ERR(dentry); |
| 2286 | if (IS_ERR(dentry)) { |
| 2287 | mutex_unlock(&dir->d_inode->i_mutex); |
| 2288 | goto out; |
| 2289 | } |
| 2290 | } |
| 2291 | mutex_unlock(&dir->d_inode->i_mutex); |
| 2292 | |
| 2293 | done: |
| 2294 | if (!dentry->d_inode || d_is_negative(dentry)) { |
| 2295 | error = -ENOENT; |
| 2296 | dput(dentry); |
| 2297 | goto out; |
| 2298 | } |
| 2299 | path->dentry = dentry; |
| 2300 | path->mnt = nd->path.mnt; |
| 2301 | if (should_follow_link(dentry, nd->flags & LOOKUP_FOLLOW)) |
| 2302 | return 1; |
| 2303 | mntget(path->mnt); |
| 2304 | follow_mount(path); |
| 2305 | error = 0; |
| 2306 | out: |
| 2307 | terminate_walk(nd); |
| 2308 | return error; |
| 2309 | } |
| 2310 | |
| 2311 | /** |
| 2312 | * path_mountpoint - look up a path to be umounted |
| 2313 | * @dfd: directory file descriptor to start walk from |
| 2314 | * @name: full pathname to walk |
| 2315 | * @path: pointer to container for result |
| 2316 | * @flags: lookup flags |
| 2317 | * |
| 2318 | * Look up the given name, but don't attempt to revalidate the last component. |
| 2319 | * Returns 0 and "path" will be valid on success; Returns error otherwise. |
| 2320 | */ |
| 2321 | static int |
| 2322 | path_mountpoint(int dfd, const char *name, struct path *path, unsigned int flags) |
| 2323 | { |
| 2324 | struct nameidata nd; |
| 2325 | int err; |
| 2326 | |
| 2327 | err = path_init(dfd, name, flags, &nd); |
| 2328 | if (unlikely(err)) |
| 2329 | goto out; |
| 2330 | |
| 2331 | err = mountpoint_last(&nd, path); |
| 2332 | while (err > 0) { |
| 2333 | void *cookie; |
| 2334 | struct path link = *path; |
| 2335 | err = may_follow_link(&link, &nd); |
| 2336 | if (unlikely(err)) |
| 2337 | break; |
| 2338 | nd.flags |= LOOKUP_PARENT; |
| 2339 | err = follow_link(&link, &nd, &cookie); |
| 2340 | if (err) |
| 2341 | break; |
| 2342 | err = mountpoint_last(&nd, path); |
| 2343 | put_link(&nd, &link, cookie); |
| 2344 | } |
| 2345 | out: |
| 2346 | path_cleanup(&nd); |
| 2347 | return err; |
| 2348 | } |
| 2349 | |
| 2350 | static int |
| 2351 | filename_mountpoint(int dfd, struct filename *s, struct path *path, |
| 2352 | unsigned int flags) |
| 2353 | { |
| 2354 | int error = path_mountpoint(dfd, s->name, path, flags | LOOKUP_RCU); |
| 2355 | if (unlikely(error == -ECHILD)) |
| 2356 | error = path_mountpoint(dfd, s->name, path, flags); |
| 2357 | if (unlikely(error == -ESTALE)) |
| 2358 | error = path_mountpoint(dfd, s->name, path, flags | LOOKUP_REVAL); |
| 2359 | if (likely(!error)) |
| 2360 | audit_inode(s, path->dentry, 0); |
| 2361 | return error; |
| 2362 | } |
| 2363 | |
| 2364 | /** |
| 2365 | * user_path_mountpoint_at - lookup a path from userland in order to umount it |
| 2366 | * @dfd: directory file descriptor |
| 2367 | * @name: pathname from userland |
| 2368 | * @flags: lookup flags |
| 2369 | * @path: pointer to container to hold result |
| 2370 | * |
| 2371 | * A umount is a special case for path walking. We're not actually interested |
| 2372 | * in the inode in this situation, and ESTALE errors can be a problem. We |
| 2373 | * simply want track down the dentry and vfsmount attached at the mountpoint |
| 2374 | * and avoid revalidating the last component. |
| 2375 | * |
| 2376 | * Returns 0 and populates "path" on success. |
| 2377 | */ |
| 2378 | int |
| 2379 | user_path_mountpoint_at(int dfd, const char __user *name, unsigned int flags, |
| 2380 | struct path *path) |
| 2381 | { |
| 2382 | struct filename *s = getname(name); |
| 2383 | int error; |
| 2384 | if (IS_ERR(s)) |
| 2385 | return PTR_ERR(s); |
| 2386 | error = filename_mountpoint(dfd, s, path, flags); |
| 2387 | putname(s); |
| 2388 | return error; |
| 2389 | } |
| 2390 | |
| 2391 | int |
| 2392 | kern_path_mountpoint(int dfd, const char *name, struct path *path, |
| 2393 | unsigned int flags) |
| 2394 | { |
| 2395 | struct filename s = {.name = name}; |
| 2396 | return filename_mountpoint(dfd, &s, path, flags); |
| 2397 | } |
| 2398 | EXPORT_SYMBOL(kern_path_mountpoint); |
| 2399 | |
| 2400 | int __check_sticky(struct inode *dir, struct inode *inode) |
| 2401 | { |
| 2402 | kuid_t fsuid = current_fsuid(); |
| 2403 | |
| 2404 | if (uid_eq(inode->i_uid, fsuid)) |
| 2405 | return 0; |
| 2406 | if (uid_eq(dir->i_uid, fsuid)) |
| 2407 | return 0; |
| 2408 | return !capable_wrt_inode_uidgid(inode, CAP_FOWNER); |
| 2409 | } |
| 2410 | EXPORT_SYMBOL(__check_sticky); |
| 2411 | |
| 2412 | /* |
| 2413 | * Check whether we can remove a link victim from directory dir, check |
| 2414 | * whether the type of victim is right. |
| 2415 | * 1. We can't do it if dir is read-only (done in permission()) |
| 2416 | * 2. We should have write and exec permissions on dir |
| 2417 | * 3. We can't remove anything from append-only dir |
| 2418 | * 4. We can't do anything with immutable dir (done in permission()) |
| 2419 | * 5. If the sticky bit on dir is set we should either |
| 2420 | * a. be owner of dir, or |
| 2421 | * b. be owner of victim, or |
| 2422 | * c. have CAP_FOWNER capability |
| 2423 | * 6. If the victim is append-only or immutable we can't do antyhing with |
| 2424 | * links pointing to it. |
| 2425 | * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR. |
| 2426 | * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR. |
| 2427 | * 9. We can't remove a root or mountpoint. |
| 2428 | * 10. We don't allow removal of NFS sillyrenamed files; it's handled by |
| 2429 | * nfs_async_unlink(). |
| 2430 | */ |
| 2431 | static int may_delete(struct inode *dir, struct dentry *victim, bool isdir) |
| 2432 | { |
| 2433 | struct inode *inode = victim->d_inode; |
| 2434 | int error; |
| 2435 | |
| 2436 | if (d_is_negative(victim)) |
| 2437 | return -ENOENT; |
| 2438 | BUG_ON(!inode); |
| 2439 | |
| 2440 | BUG_ON(victim->d_parent->d_inode != dir); |
| 2441 | audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE); |
| 2442 | |
| 2443 | error = inode_permission(dir, MAY_WRITE | MAY_EXEC); |
| 2444 | if (error) |
| 2445 | return error; |
| 2446 | if (IS_APPEND(dir)) |
| 2447 | return -EPERM; |
| 2448 | |
| 2449 | if (check_sticky(dir, inode) || IS_APPEND(inode) || |
| 2450 | IS_IMMUTABLE(inode) || IS_SWAPFILE(inode)) |
| 2451 | return -EPERM; |
| 2452 | if (isdir) { |
| 2453 | if (!d_is_dir(victim)) |
| 2454 | return -ENOTDIR; |
| 2455 | if (IS_ROOT(victim)) |
| 2456 | return -EBUSY; |
| 2457 | } else if (d_is_dir(victim)) |
| 2458 | return -EISDIR; |
| 2459 | if (IS_DEADDIR(dir)) |
| 2460 | return -ENOENT; |
| 2461 | if (victim->d_flags & DCACHE_NFSFS_RENAMED) |
| 2462 | return -EBUSY; |
| 2463 | return 0; |
| 2464 | } |
| 2465 | |
| 2466 | /* Check whether we can create an object with dentry child in directory |
| 2467 | * dir. |
| 2468 | * 1. We can't do it if child already exists (open has special treatment for |
| 2469 | * this case, but since we are inlined it's OK) |
| 2470 | * 2. We can't do it if dir is read-only (done in permission()) |
| 2471 | * 3. We should have write and exec permissions on dir |
| 2472 | * 4. We can't do it if dir is immutable (done in permission()) |
| 2473 | */ |
| 2474 | static inline int may_create(struct inode *dir, struct dentry *child) |
| 2475 | { |
| 2476 | audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE); |
| 2477 | if (child->d_inode) |
| 2478 | return -EEXIST; |
| 2479 | if (IS_DEADDIR(dir)) |
| 2480 | return -ENOENT; |
| 2481 | return inode_permission(dir, MAY_WRITE | MAY_EXEC); |
| 2482 | } |
| 2483 | |
| 2484 | /* |
| 2485 | * p1 and p2 should be directories on the same fs. |
| 2486 | */ |
| 2487 | struct dentry *lock_rename(struct dentry *p1, struct dentry *p2) |
| 2488 | { |
| 2489 | struct dentry *p; |
| 2490 | |
| 2491 | if (p1 == p2) { |
| 2492 | mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT); |
| 2493 | return NULL; |
| 2494 | } |
| 2495 | |
| 2496 | mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex); |
| 2497 | |
| 2498 | p = d_ancestor(p2, p1); |
| 2499 | if (p) { |
| 2500 | mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT); |
| 2501 | mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD); |
| 2502 | return p; |
| 2503 | } |
| 2504 | |
| 2505 | p = d_ancestor(p1, p2); |
| 2506 | if (p) { |
| 2507 | mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT); |
| 2508 | mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD); |
| 2509 | return p; |
| 2510 | } |
| 2511 | |
| 2512 | mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT); |
| 2513 | mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT2); |
| 2514 | return NULL; |
| 2515 | } |
| 2516 | EXPORT_SYMBOL(lock_rename); |
| 2517 | |
| 2518 | void unlock_rename(struct dentry *p1, struct dentry *p2) |
| 2519 | { |
| 2520 | mutex_unlock(&p1->d_inode->i_mutex); |
| 2521 | if (p1 != p2) { |
| 2522 | mutex_unlock(&p2->d_inode->i_mutex); |
| 2523 | mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex); |
| 2524 | } |
| 2525 | } |
| 2526 | EXPORT_SYMBOL(unlock_rename); |
| 2527 | |
| 2528 | int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, |
| 2529 | bool want_excl) |
| 2530 | { |
| 2531 | int error = may_create(dir, dentry); |
| 2532 | if (error) |
| 2533 | return error; |
| 2534 | |
| 2535 | if (!dir->i_op->create) |
| 2536 | return -EACCES; /* shouldn't it be ENOSYS? */ |
| 2537 | mode &= S_IALLUGO; |
| 2538 | mode |= S_IFREG; |
| 2539 | error = security_inode_create(dir, dentry, mode); |
| 2540 | if (error) |
| 2541 | return error; |
| 2542 | error = dir->i_op->create(dir, dentry, mode, want_excl); |
| 2543 | if (!error) |
| 2544 | fsnotify_create(dir, dentry); |
| 2545 | return error; |
| 2546 | } |
| 2547 | EXPORT_SYMBOL(vfs_create); |
| 2548 | |
| 2549 | static int may_open(struct path *path, int acc_mode, int flag) |
| 2550 | { |
| 2551 | struct dentry *dentry = path->dentry; |
| 2552 | struct inode *inode = dentry->d_inode; |
| 2553 | int error; |
| 2554 | |
| 2555 | /* O_PATH? */ |
| 2556 | if (!acc_mode) |
| 2557 | return 0; |
| 2558 | |
| 2559 | if (!inode) |
| 2560 | return -ENOENT; |
| 2561 | |
| 2562 | switch (inode->i_mode & S_IFMT) { |
| 2563 | case S_IFLNK: |
| 2564 | return -ELOOP; |
| 2565 | case S_IFDIR: |
| 2566 | if (acc_mode & MAY_WRITE) |
| 2567 | return -EISDIR; |
| 2568 | break; |
| 2569 | case S_IFBLK: |
| 2570 | case S_IFCHR: |
| 2571 | if (path->mnt->mnt_flags & MNT_NODEV) |
| 2572 | return -EACCES; |
| 2573 | /*FALLTHRU*/ |
| 2574 | case S_IFIFO: |
| 2575 | case S_IFSOCK: |
| 2576 | flag &= ~O_TRUNC; |
| 2577 | break; |
| 2578 | } |
| 2579 | |
| 2580 | error = inode_permission(inode, acc_mode); |
| 2581 | if (error) |
| 2582 | return error; |
| 2583 | |
| 2584 | /* |
| 2585 | * An append-only file must be opened in append mode for writing. |
| 2586 | */ |
| 2587 | if (IS_APPEND(inode)) { |
| 2588 | if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND)) |
| 2589 | return -EPERM; |
| 2590 | if (flag & O_TRUNC) |
| 2591 | return -EPERM; |
| 2592 | } |
| 2593 | |
| 2594 | /* O_NOATIME can only be set by the owner or superuser */ |
| 2595 | if (flag & O_NOATIME && !inode_owner_or_capable(inode)) |
| 2596 | return -EPERM; |
| 2597 | |
| 2598 | return 0; |
| 2599 | } |
| 2600 | |
| 2601 | static int handle_truncate(struct file *filp) |
| 2602 | { |
| 2603 | struct path *path = &filp->f_path; |
| 2604 | struct inode *inode = path->dentry->d_inode; |
| 2605 | int error = get_write_access(inode); |
| 2606 | if (error) |
| 2607 | return error; |
| 2608 | /* |
| 2609 | * Refuse to truncate files with mandatory locks held on them. |
| 2610 | */ |
| 2611 | error = locks_verify_locked(filp); |
| 2612 | if (!error) |
| 2613 | error = security_path_truncate(path); |
| 2614 | if (!error) { |
| 2615 | error = do_truncate(path->dentry, 0, |
| 2616 | ATTR_MTIME|ATTR_CTIME|ATTR_OPEN, |
| 2617 | filp); |
| 2618 | } |
| 2619 | put_write_access(inode); |
| 2620 | return error; |
| 2621 | } |
| 2622 | |
| 2623 | static inline int open_to_namei_flags(int flag) |
| 2624 | { |
| 2625 | if ((flag & O_ACCMODE) == 3) |
| 2626 | flag--; |
| 2627 | return flag; |
| 2628 | } |
| 2629 | |
| 2630 | static int may_o_create(struct path *dir, struct dentry *dentry, umode_t mode) |
| 2631 | { |
| 2632 | int error = security_path_mknod(dir, dentry, mode, 0); |
| 2633 | if (error) |
| 2634 | return error; |
| 2635 | |
| 2636 | error = inode_permission(dir->dentry->d_inode, MAY_WRITE | MAY_EXEC); |
| 2637 | if (error) |
| 2638 | return error; |
| 2639 | |
| 2640 | return security_inode_create(dir->dentry->d_inode, dentry, mode); |
| 2641 | } |
| 2642 | |
| 2643 | /* |
| 2644 | * Attempt to atomically look up, create and open a file from a negative |
| 2645 | * dentry. |
| 2646 | * |
| 2647 | * Returns 0 if successful. The file will have been created and attached to |
| 2648 | * @file by the filesystem calling finish_open(). |
| 2649 | * |
| 2650 | * Returns 1 if the file was looked up only or didn't need creating. The |
| 2651 | * caller will need to perform the open themselves. @path will have been |
| 2652 | * updated to point to the new dentry. This may be negative. |
| 2653 | * |
| 2654 | * Returns an error code otherwise. |
| 2655 | */ |
| 2656 | static int atomic_open(struct nameidata *nd, struct dentry *dentry, |
| 2657 | struct path *path, struct file *file, |
| 2658 | const struct open_flags *op, |
| 2659 | bool got_write, bool need_lookup, |
| 2660 | int *opened) |
| 2661 | { |
| 2662 | struct inode *dir = nd->path.dentry->d_inode; |
| 2663 | unsigned open_flag = open_to_namei_flags(op->open_flag); |
| 2664 | umode_t mode; |
| 2665 | int error; |
| 2666 | int acc_mode; |
| 2667 | int create_error = 0; |
| 2668 | struct dentry *const DENTRY_NOT_SET = (void *) -1UL; |
| 2669 | bool excl; |
| 2670 | |
| 2671 | BUG_ON(dentry->d_inode); |
| 2672 | |
| 2673 | /* Don't create child dentry for a dead directory. */ |
| 2674 | if (unlikely(IS_DEADDIR(dir))) { |
| 2675 | error = -ENOENT; |
| 2676 | goto out; |
| 2677 | } |
| 2678 | |
| 2679 | mode = op->mode; |
| 2680 | if ((open_flag & O_CREAT) && !IS_POSIXACL(dir)) |
| 2681 | mode &= ~current_umask(); |
| 2682 | |
| 2683 | excl = (open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT); |
| 2684 | if (excl) |
| 2685 | open_flag &= ~O_TRUNC; |
| 2686 | |
| 2687 | /* |
| 2688 | * Checking write permission is tricky, bacuse we don't know if we are |
| 2689 | * going to actually need it: O_CREAT opens should work as long as the |
| 2690 | * file exists. But checking existence breaks atomicity. The trick is |
| 2691 | * to check access and if not granted clear O_CREAT from the flags. |
| 2692 | * |
| 2693 | * Another problem is returing the "right" error value (e.g. for an |
| 2694 | * O_EXCL open we want to return EEXIST not EROFS). |
| 2695 | */ |
| 2696 | if (((open_flag & (O_CREAT | O_TRUNC)) || |
| 2697 | (open_flag & O_ACCMODE) != O_RDONLY) && unlikely(!got_write)) { |
| 2698 | if (!(open_flag & O_CREAT)) { |
| 2699 | /* |
| 2700 | * No O_CREATE -> atomicity not a requirement -> fall |
| 2701 | * back to lookup + open |
| 2702 | */ |
| 2703 | goto no_open; |
| 2704 | } else if (open_flag & (O_EXCL | O_TRUNC)) { |
| 2705 | /* Fall back and fail with the right error */ |
| 2706 | create_error = -EROFS; |
| 2707 | goto no_open; |
| 2708 | } else { |
| 2709 | /* No side effects, safe to clear O_CREAT */ |
| 2710 | create_error = -EROFS; |
| 2711 | open_flag &= ~O_CREAT; |
| 2712 | } |
| 2713 | } |
| 2714 | |
| 2715 | if (open_flag & O_CREAT) { |
| 2716 | error = may_o_create(&nd->path, dentry, mode); |
| 2717 | if (error) { |
| 2718 | create_error = error; |
| 2719 | if (open_flag & O_EXCL) |
| 2720 | goto no_open; |
| 2721 | open_flag &= ~O_CREAT; |
| 2722 | } |
| 2723 | } |
| 2724 | |
| 2725 | if (nd->flags & LOOKUP_DIRECTORY) |
| 2726 | open_flag |= O_DIRECTORY; |
| 2727 | |
| 2728 | file->f_path.dentry = DENTRY_NOT_SET; |
| 2729 | file->f_path.mnt = nd->path.mnt; |
| 2730 | error = dir->i_op->atomic_open(dir, dentry, file, open_flag, mode, |
| 2731 | opened); |
| 2732 | if (error < 0) { |
| 2733 | if (create_error && error == -ENOENT) |
| 2734 | error = create_error; |
| 2735 | goto out; |
| 2736 | } |
| 2737 | |
| 2738 | if (error) { /* returned 1, that is */ |
| 2739 | if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) { |
| 2740 | error = -EIO; |
| 2741 | goto out; |
| 2742 | } |
| 2743 | if (file->f_path.dentry) { |
| 2744 | dput(dentry); |
| 2745 | dentry = file->f_path.dentry; |
| 2746 | } |
| 2747 | if (*opened & FILE_CREATED) |
| 2748 | fsnotify_create(dir, dentry); |
| 2749 | if (!dentry->d_inode) { |
| 2750 | WARN_ON(*opened & FILE_CREATED); |
| 2751 | if (create_error) { |
| 2752 | error = create_error; |
| 2753 | goto out; |
| 2754 | } |
| 2755 | } else { |
| 2756 | if (excl && !(*opened & FILE_CREATED)) { |
| 2757 | error = -EEXIST; |
| 2758 | goto out; |
| 2759 | } |
| 2760 | } |
| 2761 | goto looked_up; |
| 2762 | } |
| 2763 | |
| 2764 | /* |
| 2765 | * We didn't have the inode before the open, so check open permission |
| 2766 | * here. |
| 2767 | */ |
| 2768 | acc_mode = op->acc_mode; |
| 2769 | if (*opened & FILE_CREATED) { |
| 2770 | WARN_ON(!(open_flag & O_CREAT)); |
| 2771 | fsnotify_create(dir, dentry); |
| 2772 | acc_mode = MAY_OPEN; |
| 2773 | } |
| 2774 | error = may_open(&file->f_path, acc_mode, open_flag); |
| 2775 | if (error) |
| 2776 | fput(file); |
| 2777 | |
| 2778 | out: |
| 2779 | dput(dentry); |
| 2780 | return error; |
| 2781 | |
| 2782 | no_open: |
| 2783 | if (need_lookup) { |
| 2784 | dentry = lookup_real(dir, dentry, nd->flags); |
| 2785 | if (IS_ERR(dentry)) |
| 2786 | return PTR_ERR(dentry); |
| 2787 | |
| 2788 | if (create_error) { |
| 2789 | int open_flag = op->open_flag; |
| 2790 | |
| 2791 | error = create_error; |
| 2792 | if ((open_flag & O_EXCL)) { |
| 2793 | if (!dentry->d_inode) |
| 2794 | goto out; |
| 2795 | } else if (!dentry->d_inode) { |
| 2796 | goto out; |
| 2797 | } else if ((open_flag & O_TRUNC) && |
| 2798 | S_ISREG(dentry->d_inode->i_mode)) { |
| 2799 | goto out; |
| 2800 | } |
| 2801 | /* will fail later, go on to get the right error */ |
| 2802 | } |
| 2803 | } |
| 2804 | looked_up: |
| 2805 | path->dentry = dentry; |
| 2806 | path->mnt = nd->path.mnt; |
| 2807 | return 1; |
| 2808 | } |
| 2809 | |
| 2810 | /* |
| 2811 | * Look up and maybe create and open the last component. |
| 2812 | * |
| 2813 | * Must be called with i_mutex held on parent. |
| 2814 | * |
| 2815 | * Returns 0 if the file was successfully atomically created (if necessary) and |
| 2816 | * opened. In this case the file will be returned attached to @file. |
| 2817 | * |
| 2818 | * Returns 1 if the file was not completely opened at this time, though lookups |
| 2819 | * and creations will have been performed and the dentry returned in @path will |
| 2820 | * be positive upon return if O_CREAT was specified. If O_CREAT wasn't |
| 2821 | * specified then a negative dentry may be returned. |
| 2822 | * |
| 2823 | * An error code is returned otherwise. |
| 2824 | * |
| 2825 | * FILE_CREATE will be set in @*opened if the dentry was created and will be |
| 2826 | * cleared otherwise prior to returning. |
| 2827 | */ |
| 2828 | static int lookup_open(struct nameidata *nd, struct path *path, |
| 2829 | struct file *file, |
| 2830 | const struct open_flags *op, |
| 2831 | bool got_write, int *opened) |
| 2832 | { |
| 2833 | struct dentry *dir = nd->path.dentry; |
| 2834 | struct inode *dir_inode = dir->d_inode; |
| 2835 | struct dentry *dentry; |
| 2836 | int error; |
| 2837 | bool need_lookup; |
| 2838 | |
| 2839 | *opened &= ~FILE_CREATED; |
| 2840 | dentry = lookup_dcache(&nd->last, dir, nd->flags, &need_lookup); |
| 2841 | if (IS_ERR(dentry)) |
| 2842 | return PTR_ERR(dentry); |
| 2843 | |
| 2844 | /* Cached positive dentry: will open in f_op->open */ |
| 2845 | if (!need_lookup && dentry->d_inode) |
| 2846 | goto out_no_open; |
| 2847 | |
| 2848 | if ((nd->flags & LOOKUP_OPEN) && dir_inode->i_op->atomic_open) { |
| 2849 | return atomic_open(nd, dentry, path, file, op, got_write, |
| 2850 | need_lookup, opened); |
| 2851 | } |
| 2852 | |
| 2853 | if (need_lookup) { |
| 2854 | BUG_ON(dentry->d_inode); |
| 2855 | |
| 2856 | dentry = lookup_real(dir_inode, dentry, nd->flags); |
| 2857 | if (IS_ERR(dentry)) |
| 2858 | return PTR_ERR(dentry); |
| 2859 | } |
| 2860 | |
| 2861 | /* Negative dentry, just create the file */ |
| 2862 | if (!dentry->d_inode && (op->open_flag & O_CREAT)) { |
| 2863 | umode_t mode = op->mode; |
| 2864 | if (!IS_POSIXACL(dir->d_inode)) |
| 2865 | mode &= ~current_umask(); |
| 2866 | /* |
| 2867 | * This write is needed to ensure that a |
| 2868 | * rw->ro transition does not occur between |
| 2869 | * the time when the file is created and when |
| 2870 | * a permanent write count is taken through |
| 2871 | * the 'struct file' in finish_open(). |
| 2872 | */ |
| 2873 | if (!got_write) { |
| 2874 | error = -EROFS; |
| 2875 | goto out_dput; |
| 2876 | } |
| 2877 | *opened |= FILE_CREATED; |
| 2878 | error = security_path_mknod(&nd->path, dentry, mode, 0); |
| 2879 | if (error) |
| 2880 | goto out_dput; |
| 2881 | error = vfs_create(dir->d_inode, dentry, mode, |
| 2882 | nd->flags & LOOKUP_EXCL); |
| 2883 | if (error) |
| 2884 | goto out_dput; |
| 2885 | } |
| 2886 | out_no_open: |
| 2887 | path->dentry = dentry; |
| 2888 | path->mnt = nd->path.mnt; |
| 2889 | return 1; |
| 2890 | |
| 2891 | out_dput: |
| 2892 | dput(dentry); |
| 2893 | return error; |
| 2894 | } |
| 2895 | |
| 2896 | /* |
| 2897 | * Handle the last step of open() |
| 2898 | */ |
| 2899 | static int do_last(struct nameidata *nd, struct path *path, |
| 2900 | struct file *file, const struct open_flags *op, |
| 2901 | int *opened, struct filename *name) |
| 2902 | { |
| 2903 | struct dentry *dir = nd->path.dentry; |
| 2904 | int open_flag = op->open_flag; |
| 2905 | bool will_truncate = (open_flag & O_TRUNC) != 0; |
| 2906 | bool got_write = false; |
| 2907 | int acc_mode = op->acc_mode; |
| 2908 | struct inode *inode; |
| 2909 | bool symlink_ok = false; |
| 2910 | struct path save_parent = { .dentry = NULL, .mnt = NULL }; |
| 2911 | bool retried = false; |
| 2912 | int error; |
| 2913 | |
| 2914 | nd->flags &= ~LOOKUP_PARENT; |
| 2915 | nd->flags |= op->intent; |
| 2916 | |
| 2917 | if (nd->last_type != LAST_NORM) { |
| 2918 | error = handle_dots(nd, nd->last_type); |
| 2919 | if (error) |
| 2920 | return error; |
| 2921 | goto finish_open; |
| 2922 | } |
| 2923 | |
| 2924 | if (!(open_flag & O_CREAT)) { |
| 2925 | if (nd->last.name[nd->last.len]) |
| 2926 | nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; |
| 2927 | if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW)) |
| 2928 | symlink_ok = true; |
| 2929 | /* we _can_ be in RCU mode here */ |
| 2930 | error = lookup_fast(nd, path, &inode); |
| 2931 | if (likely(!error)) |
| 2932 | goto finish_lookup; |
| 2933 | |
| 2934 | if (error < 0) |
| 2935 | goto out; |
| 2936 | |
| 2937 | BUG_ON(nd->inode != dir->d_inode); |
| 2938 | } else { |
| 2939 | /* create side of things */ |
| 2940 | /* |
| 2941 | * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED |
| 2942 | * has been cleared when we got to the last component we are |
| 2943 | * about to look up |
| 2944 | */ |
| 2945 | error = complete_walk(nd); |
| 2946 | if (error) |
| 2947 | return error; |
| 2948 | |
| 2949 | audit_inode(name, dir, LOOKUP_PARENT); |
| 2950 | error = -EISDIR; |
| 2951 | /* trailing slashes? */ |
| 2952 | if (nd->last.name[nd->last.len]) |
| 2953 | goto out; |
| 2954 | } |
| 2955 | |
| 2956 | retry_lookup: |
| 2957 | if (op->open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) { |
| 2958 | error = mnt_want_write(nd->path.mnt); |
| 2959 | if (!error) |
| 2960 | got_write = true; |
| 2961 | /* |
| 2962 | * do _not_ fail yet - we might not need that or fail with |
| 2963 | * a different error; let lookup_open() decide; we'll be |
| 2964 | * dropping this one anyway. |
| 2965 | */ |
| 2966 | } |
| 2967 | mutex_lock(&dir->d_inode->i_mutex); |
| 2968 | error = lookup_open(nd, path, file, op, got_write, opened); |
| 2969 | mutex_unlock(&dir->d_inode->i_mutex); |
| 2970 | |
| 2971 | if (error <= 0) { |
| 2972 | if (error) |
| 2973 | goto out; |
| 2974 | |
| 2975 | if ((*opened & FILE_CREATED) || |
| 2976 | !S_ISREG(file_inode(file)->i_mode)) |
| 2977 | will_truncate = false; |
| 2978 | |
| 2979 | audit_inode(name, file->f_path.dentry, 0); |
| 2980 | goto opened; |
| 2981 | } |
| 2982 | |
| 2983 | if (*opened & FILE_CREATED) { |
| 2984 | /* Don't check for write permission, don't truncate */ |
| 2985 | open_flag &= ~O_TRUNC; |
| 2986 | will_truncate = false; |
| 2987 | acc_mode = MAY_OPEN; |
| 2988 | path_to_nameidata(path, nd); |
| 2989 | goto finish_open_created; |
| 2990 | } |
| 2991 | |
| 2992 | /* |
| 2993 | * create/update audit record if it already exists. |
| 2994 | */ |
| 2995 | if (d_is_positive(path->dentry)) |
| 2996 | audit_inode(name, path->dentry, 0); |
| 2997 | |
| 2998 | /* |
| 2999 | * If atomic_open() acquired write access it is dropped now due to |
| 3000 | * possible mount and symlink following (this might be optimized away if |
| 3001 | * necessary...) |
| 3002 | */ |
| 3003 | if (got_write) { |
| 3004 | mnt_drop_write(nd->path.mnt); |
| 3005 | got_write = false; |
| 3006 | } |
| 3007 | |
| 3008 | error = -EEXIST; |
| 3009 | if ((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT)) |
| 3010 | goto exit_dput; |
| 3011 | |
| 3012 | error = follow_managed(path, nd->flags); |
| 3013 | if (error < 0) |
| 3014 | goto exit_dput; |
| 3015 | |
| 3016 | if (error) |
| 3017 | nd->flags |= LOOKUP_JUMPED; |
| 3018 | |
| 3019 | BUG_ON(nd->flags & LOOKUP_RCU); |
| 3020 | inode = path->dentry->d_inode; |
| 3021 | finish_lookup: |
| 3022 | /* we _can_ be in RCU mode here */ |
| 3023 | error = -ENOENT; |
| 3024 | if (!inode || d_is_negative(path->dentry)) { |
| 3025 | path_to_nameidata(path, nd); |
| 3026 | goto out; |
| 3027 | } |
| 3028 | |
| 3029 | if (should_follow_link(path->dentry, !symlink_ok)) { |
| 3030 | if (nd->flags & LOOKUP_RCU) { |
| 3031 | if (unlikely(unlazy_walk(nd, path->dentry))) { |
| 3032 | error = -ECHILD; |
| 3033 | goto out; |
| 3034 | } |
| 3035 | } |
| 3036 | BUG_ON(inode != path->dentry->d_inode); |
| 3037 | return 1; |
| 3038 | } |
| 3039 | |
| 3040 | if ((nd->flags & LOOKUP_RCU) || nd->path.mnt != path->mnt) { |
| 3041 | path_to_nameidata(path, nd); |
| 3042 | } else { |
| 3043 | save_parent.dentry = nd->path.dentry; |
| 3044 | save_parent.mnt = mntget(path->mnt); |
| 3045 | nd->path.dentry = path->dentry; |
| 3046 | |
| 3047 | } |
| 3048 | nd->inode = inode; |
| 3049 | /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */ |
| 3050 | finish_open: |
| 3051 | error = complete_walk(nd); |
| 3052 | if (error) { |
| 3053 | path_put(&save_parent); |
| 3054 | return error; |
| 3055 | } |
| 3056 | audit_inode(name, nd->path.dentry, 0); |
| 3057 | error = -EISDIR; |
| 3058 | if ((open_flag & O_CREAT) && d_is_dir(nd->path.dentry)) |
| 3059 | goto out; |
| 3060 | error = -ENOTDIR; |
| 3061 | if ((nd->flags & LOOKUP_DIRECTORY) && !d_can_lookup(nd->path.dentry)) |
| 3062 | goto out; |
| 3063 | if (!S_ISREG(nd->inode->i_mode)) |
| 3064 | will_truncate = false; |
| 3065 | |
| 3066 | if (will_truncate) { |
| 3067 | error = mnt_want_write(nd->path.mnt); |
| 3068 | if (error) |
| 3069 | goto out; |
| 3070 | got_write = true; |
| 3071 | } |
| 3072 | finish_open_created: |
| 3073 | error = may_open(&nd->path, acc_mode, open_flag); |
| 3074 | if (error) |
| 3075 | goto out; |
| 3076 | |
| 3077 | BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */ |
| 3078 | error = vfs_open(&nd->path, file, current_cred()); |
| 3079 | if (!error) { |
| 3080 | *opened |= FILE_OPENED; |
| 3081 | } else { |
| 3082 | if (error == -EOPENSTALE) |
| 3083 | goto stale_open; |
| 3084 | goto out; |
| 3085 | } |
| 3086 | opened: |
| 3087 | error = open_check_o_direct(file); |
| 3088 | if (error) |
| 3089 | goto exit_fput; |
| 3090 | error = ima_file_check(file, op->acc_mode, *opened); |
| 3091 | if (error) |
| 3092 | goto exit_fput; |
| 3093 | |
| 3094 | if (will_truncate) { |
| 3095 | error = handle_truncate(file); |
| 3096 | if (error) |
| 3097 | goto exit_fput; |
| 3098 | } |
| 3099 | out: |
| 3100 | if (got_write) |
| 3101 | mnt_drop_write(nd->path.mnt); |
| 3102 | path_put(&save_parent); |
| 3103 | terminate_walk(nd); |
| 3104 | return error; |
| 3105 | |
| 3106 | exit_dput: |
| 3107 | path_put_conditional(path, nd); |
| 3108 | goto out; |
| 3109 | exit_fput: |
| 3110 | fput(file); |
| 3111 | goto out; |
| 3112 | |
| 3113 | stale_open: |
| 3114 | /* If no saved parent or already retried then can't retry */ |
| 3115 | if (!save_parent.dentry || retried) |
| 3116 | goto out; |
| 3117 | |
| 3118 | BUG_ON(save_parent.dentry != dir); |
| 3119 | path_put(&nd->path); |
| 3120 | nd->path = save_parent; |
| 3121 | nd->inode = dir->d_inode; |
| 3122 | save_parent.mnt = NULL; |
| 3123 | save_parent.dentry = NULL; |
| 3124 | if (got_write) { |
| 3125 | mnt_drop_write(nd->path.mnt); |
| 3126 | got_write = false; |
| 3127 | } |
| 3128 | retried = true; |
| 3129 | goto retry_lookup; |
| 3130 | } |
| 3131 | |
| 3132 | static int do_tmpfile(int dfd, struct filename *pathname, |
| 3133 | struct nameidata *nd, int flags, |
| 3134 | const struct open_flags *op, |
| 3135 | struct file *file, int *opened) |
| 3136 | { |
| 3137 | static const struct qstr name = QSTR_INIT("/", 1); |
| 3138 | struct dentry *dentry, *child; |
| 3139 | struct inode *dir; |
| 3140 | int error = path_lookupat(dfd, pathname->name, |
| 3141 | flags | LOOKUP_DIRECTORY, nd); |
| 3142 | if (unlikely(error)) |
| 3143 | return error; |
| 3144 | error = mnt_want_write(nd->path.mnt); |
| 3145 | if (unlikely(error)) |
| 3146 | goto out; |
| 3147 | /* we want directory to be writable */ |
| 3148 | error = inode_permission(nd->inode, MAY_WRITE | MAY_EXEC); |
| 3149 | if (error) |
| 3150 | goto out2; |
| 3151 | dentry = nd->path.dentry; |
| 3152 | dir = dentry->d_inode; |
| 3153 | if (!dir->i_op->tmpfile) { |
| 3154 | error = -EOPNOTSUPP; |
| 3155 | goto out2; |
| 3156 | } |
| 3157 | child = d_alloc(dentry, &name); |
| 3158 | if (unlikely(!child)) { |
| 3159 | error = -ENOMEM; |
| 3160 | goto out2; |
| 3161 | } |
| 3162 | nd->flags &= ~LOOKUP_DIRECTORY; |
| 3163 | nd->flags |= op->intent; |
| 3164 | dput(nd->path.dentry); |
| 3165 | nd->path.dentry = child; |
| 3166 | error = dir->i_op->tmpfile(dir, nd->path.dentry, op->mode); |
| 3167 | if (error) |
| 3168 | goto out2; |
| 3169 | audit_inode(pathname, nd->path.dentry, 0); |
| 3170 | /* Don't check for other permissions, the inode was just created */ |
| 3171 | error = may_open(&nd->path, MAY_OPEN, op->open_flag); |
| 3172 | if (error) |
| 3173 | goto out2; |
| 3174 | file->f_path.mnt = nd->path.mnt; |
| 3175 | error = finish_open(file, nd->path.dentry, NULL, opened); |
| 3176 | if (error) |
| 3177 | goto out2; |
| 3178 | error = open_check_o_direct(file); |
| 3179 | if (error) { |
| 3180 | fput(file); |
| 3181 | } else if (!(op->open_flag & O_EXCL)) { |
| 3182 | struct inode *inode = file_inode(file); |
| 3183 | spin_lock(&inode->i_lock); |
| 3184 | inode->i_state |= I_LINKABLE; |
| 3185 | spin_unlock(&inode->i_lock); |
| 3186 | } |
| 3187 | out2: |
| 3188 | mnt_drop_write(nd->path.mnt); |
| 3189 | out: |
| 3190 | path_put(&nd->path); |
| 3191 | return error; |
| 3192 | } |
| 3193 | |
| 3194 | static struct file *path_openat(int dfd, struct filename *pathname, |
| 3195 | struct nameidata *nd, const struct open_flags *op, int flags) |
| 3196 | { |
| 3197 | struct file *file; |
| 3198 | struct path path; |
| 3199 | int opened = 0; |
| 3200 | int error; |
| 3201 | |
| 3202 | file = get_empty_filp(); |
| 3203 | if (IS_ERR(file)) |
| 3204 | return file; |
| 3205 | |
| 3206 | file->f_flags = op->open_flag; |
| 3207 | |
| 3208 | if (unlikely(file->f_flags & __O_TMPFILE)) { |
| 3209 | error = do_tmpfile(dfd, pathname, nd, flags, op, file, &opened); |
| 3210 | goto out; |
| 3211 | } |
| 3212 | |
| 3213 | error = path_init(dfd, pathname->name, flags, nd); |
| 3214 | if (unlikely(error)) |
| 3215 | goto out; |
| 3216 | |
| 3217 | error = do_last(nd, &path, file, op, &opened, pathname); |
| 3218 | while (unlikely(error > 0)) { /* trailing symlink */ |
| 3219 | struct path link = path; |
| 3220 | void *cookie; |
| 3221 | if (!(nd->flags & LOOKUP_FOLLOW)) { |
| 3222 | path_put_conditional(&path, nd); |
| 3223 | path_put(&nd->path); |
| 3224 | error = -ELOOP; |
| 3225 | break; |
| 3226 | } |
| 3227 | error = may_follow_link(&link, nd); |
| 3228 | if (unlikely(error)) |
| 3229 | break; |
| 3230 | nd->flags |= LOOKUP_PARENT; |
| 3231 | nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL); |
| 3232 | error = follow_link(&link, nd, &cookie); |
| 3233 | if (unlikely(error)) |
| 3234 | break; |
| 3235 | error = do_last(nd, &path, file, op, &opened, pathname); |
| 3236 | put_link(nd, &link, cookie); |
| 3237 | } |
| 3238 | out: |
| 3239 | path_cleanup(nd); |
| 3240 | if (!(opened & FILE_OPENED)) { |
| 3241 | BUG_ON(!error); |
| 3242 | put_filp(file); |
| 3243 | } |
| 3244 | if (unlikely(error)) { |
| 3245 | if (error == -EOPENSTALE) { |
| 3246 | if (flags & LOOKUP_RCU) |
| 3247 | error = -ECHILD; |
| 3248 | else |
| 3249 | error = -ESTALE; |
| 3250 | } |
| 3251 | file = ERR_PTR(error); |
| 3252 | } |
| 3253 | return file; |
| 3254 | } |
| 3255 | |
| 3256 | struct file *do_filp_open(int dfd, struct filename *pathname, |
| 3257 | const struct open_flags *op) |
| 3258 | { |
| 3259 | struct nameidata nd; |
| 3260 | int flags = op->lookup_flags; |
| 3261 | struct file *filp; |
| 3262 | |
| 3263 | filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_RCU); |
| 3264 | if (unlikely(filp == ERR_PTR(-ECHILD))) |
| 3265 | filp = path_openat(dfd, pathname, &nd, op, flags); |
| 3266 | if (unlikely(filp == ERR_PTR(-ESTALE))) |
| 3267 | filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_REVAL); |
| 3268 | return filp; |
| 3269 | } |
| 3270 | |
| 3271 | struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt, |
| 3272 | const char *name, const struct open_flags *op) |
| 3273 | { |
| 3274 | struct nameidata nd; |
| 3275 | struct file *file; |
| 3276 | struct filename filename = { .name = name }; |
| 3277 | int flags = op->lookup_flags | LOOKUP_ROOT; |
| 3278 | |
| 3279 | nd.root.mnt = mnt; |
| 3280 | nd.root.dentry = dentry; |
| 3281 | |
| 3282 | if (d_is_symlink(dentry) && op->intent & LOOKUP_OPEN) |
| 3283 | return ERR_PTR(-ELOOP); |
| 3284 | |
| 3285 | file = path_openat(-1, &filename, &nd, op, flags | LOOKUP_RCU); |
| 3286 | if (unlikely(file == ERR_PTR(-ECHILD))) |
| 3287 | file = path_openat(-1, &filename, &nd, op, flags); |
| 3288 | if (unlikely(file == ERR_PTR(-ESTALE))) |
| 3289 | file = path_openat(-1, &filename, &nd, op, flags | LOOKUP_REVAL); |
| 3290 | return file; |
| 3291 | } |
| 3292 | |
| 3293 | struct dentry *kern_path_create(int dfd, const char *pathname, |
| 3294 | struct path *path, unsigned int lookup_flags) |
| 3295 | { |
| 3296 | struct dentry *dentry = ERR_PTR(-EEXIST); |
| 3297 | struct nameidata nd; |
| 3298 | int err2; |
| 3299 | int error; |
| 3300 | bool is_dir = (lookup_flags & LOOKUP_DIRECTORY); |
| 3301 | |
| 3302 | /* |
| 3303 | * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any |
| 3304 | * other flags passed in are ignored! |
| 3305 | */ |
| 3306 | lookup_flags &= LOOKUP_REVAL; |
| 3307 | |
| 3308 | error = do_path_lookup(dfd, pathname, LOOKUP_PARENT|lookup_flags, &nd); |
| 3309 | if (error) |
| 3310 | return ERR_PTR(error); |
| 3311 | |
| 3312 | /* |
| 3313 | * Yucky last component or no last component at all? |
| 3314 | * (foo/., foo/.., /////) |
| 3315 | */ |
| 3316 | if (nd.last_type != LAST_NORM) |
| 3317 | goto out; |
| 3318 | nd.flags &= ~LOOKUP_PARENT; |
| 3319 | nd.flags |= LOOKUP_CREATE | LOOKUP_EXCL; |
| 3320 | |
| 3321 | /* don't fail immediately if it's r/o, at least try to report other errors */ |
| 3322 | err2 = mnt_want_write(nd.path.mnt); |
| 3323 | /* |
| 3324 | * Do the final lookup. |
| 3325 | */ |
| 3326 | mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); |
| 3327 | dentry = lookup_hash(&nd); |
| 3328 | if (IS_ERR(dentry)) |
| 3329 | goto unlock; |
| 3330 | |
| 3331 | error = -EEXIST; |
| 3332 | if (d_is_positive(dentry)) |
| 3333 | goto fail; |
| 3334 | |
| 3335 | /* |
| 3336 | * Special case - lookup gave negative, but... we had foo/bar/ |
| 3337 | * From the vfs_mknod() POV we just have a negative dentry - |
| 3338 | * all is fine. Let's be bastards - you had / on the end, you've |
| 3339 | * been asking for (non-existent) directory. -ENOENT for you. |
| 3340 | */ |
| 3341 | if (unlikely(!is_dir && nd.last.name[nd.last.len])) { |
| 3342 | error = -ENOENT; |
| 3343 | goto fail; |
| 3344 | } |
| 3345 | if (unlikely(err2)) { |
| 3346 | error = err2; |
| 3347 | goto fail; |
| 3348 | } |
| 3349 | *path = nd.path; |
| 3350 | return dentry; |
| 3351 | fail: |
| 3352 | dput(dentry); |
| 3353 | dentry = ERR_PTR(error); |
| 3354 | unlock: |
| 3355 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); |
| 3356 | if (!err2) |
| 3357 | mnt_drop_write(nd.path.mnt); |
| 3358 | out: |
| 3359 | path_put(&nd.path); |
| 3360 | return dentry; |
| 3361 | } |
| 3362 | EXPORT_SYMBOL(kern_path_create); |
| 3363 | |
| 3364 | void done_path_create(struct path *path, struct dentry *dentry) |
| 3365 | { |
| 3366 | dput(dentry); |
| 3367 | mutex_unlock(&path->dentry->d_inode->i_mutex); |
| 3368 | mnt_drop_write(path->mnt); |
| 3369 | path_put(path); |
| 3370 | } |
| 3371 | EXPORT_SYMBOL(done_path_create); |
| 3372 | |
| 3373 | struct dentry *user_path_create(int dfd, const char __user *pathname, |
| 3374 | struct path *path, unsigned int lookup_flags) |
| 3375 | { |
| 3376 | struct filename *tmp = getname(pathname); |
| 3377 | struct dentry *res; |
| 3378 | if (IS_ERR(tmp)) |
| 3379 | return ERR_CAST(tmp); |
| 3380 | res = kern_path_create(dfd, tmp->name, path, lookup_flags); |
| 3381 | putname(tmp); |
| 3382 | return res; |
| 3383 | } |
| 3384 | EXPORT_SYMBOL(user_path_create); |
| 3385 | |
| 3386 | int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev) |
| 3387 | { |
| 3388 | int error = may_create(dir, dentry); |
| 3389 | |
| 3390 | if (error) |
| 3391 | return error; |
| 3392 | |
| 3393 | if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD)) |
| 3394 | return -EPERM; |
| 3395 | |
| 3396 | if (!dir->i_op->mknod) |
| 3397 | return -EPERM; |
| 3398 | |
| 3399 | error = devcgroup_inode_mknod(mode, dev); |
| 3400 | if (error) |
| 3401 | return error; |
| 3402 | |
| 3403 | error = security_inode_mknod(dir, dentry, mode, dev); |
| 3404 | if (error) |
| 3405 | return error; |
| 3406 | |
| 3407 | error = dir->i_op->mknod(dir, dentry, mode, dev); |
| 3408 | if (!error) |
| 3409 | fsnotify_create(dir, dentry); |
| 3410 | return error; |
| 3411 | } |
| 3412 | EXPORT_SYMBOL(vfs_mknod); |
| 3413 | |
| 3414 | static int may_mknod(umode_t mode) |
| 3415 | { |
| 3416 | switch (mode & S_IFMT) { |
| 3417 | case S_IFREG: |
| 3418 | case S_IFCHR: |
| 3419 | case S_IFBLK: |
| 3420 | case S_IFIFO: |
| 3421 | case S_IFSOCK: |
| 3422 | case 0: /* zero mode translates to S_IFREG */ |
| 3423 | return 0; |
| 3424 | case S_IFDIR: |
| 3425 | return -EPERM; |
| 3426 | default: |
| 3427 | return -EINVAL; |
| 3428 | } |
| 3429 | } |
| 3430 | |
| 3431 | SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode, |
| 3432 | unsigned, dev) |
| 3433 | { |
| 3434 | struct dentry *dentry; |
| 3435 | struct path path; |
| 3436 | int error; |
| 3437 | unsigned int lookup_flags = 0; |
| 3438 | |
| 3439 | error = may_mknod(mode); |
| 3440 | if (error) |
| 3441 | return error; |
| 3442 | retry: |
| 3443 | dentry = user_path_create(dfd, filename, &path, lookup_flags); |
| 3444 | if (IS_ERR(dentry)) |
| 3445 | return PTR_ERR(dentry); |
| 3446 | |
| 3447 | if (!IS_POSIXACL(path.dentry->d_inode)) |
| 3448 | mode &= ~current_umask(); |
| 3449 | error = security_path_mknod(&path, dentry, mode, dev); |
| 3450 | if (error) |
| 3451 | goto out; |
| 3452 | switch (mode & S_IFMT) { |
| 3453 | case 0: case S_IFREG: |
| 3454 | error = vfs_create(path.dentry->d_inode,dentry,mode,true); |
| 3455 | break; |
| 3456 | case S_IFCHR: case S_IFBLK: |
| 3457 | error = vfs_mknod(path.dentry->d_inode,dentry,mode, |
| 3458 | new_decode_dev(dev)); |
| 3459 | break; |
| 3460 | case S_IFIFO: case S_IFSOCK: |
| 3461 | error = vfs_mknod(path.dentry->d_inode,dentry,mode,0); |
| 3462 | break; |
| 3463 | } |
| 3464 | out: |
| 3465 | done_path_create(&path, dentry); |
| 3466 | if (retry_estale(error, lookup_flags)) { |
| 3467 | lookup_flags |= LOOKUP_REVAL; |
| 3468 | goto retry; |
| 3469 | } |
| 3470 | return error; |
| 3471 | } |
| 3472 | |
| 3473 | SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev) |
| 3474 | { |
| 3475 | return sys_mknodat(AT_FDCWD, filename, mode, dev); |
| 3476 | } |
| 3477 | |
| 3478 | int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode) |
| 3479 | { |
| 3480 | int error = may_create(dir, dentry); |
| 3481 | unsigned max_links = dir->i_sb->s_max_links; |
| 3482 | |
| 3483 | if (error) |
| 3484 | return error; |
| 3485 | |
| 3486 | if (!dir->i_op->mkdir) |
| 3487 | return -EPERM; |
| 3488 | |
| 3489 | mode &= (S_IRWXUGO|S_ISVTX); |
| 3490 | error = security_inode_mkdir(dir, dentry, mode); |
| 3491 | if (error) |
| 3492 | return error; |
| 3493 | |
| 3494 | if (max_links && dir->i_nlink >= max_links) |
| 3495 | return -EMLINK; |
| 3496 | |
| 3497 | error = dir->i_op->mkdir(dir, dentry, mode); |
| 3498 | if (!error) |
| 3499 | fsnotify_mkdir(dir, dentry); |
| 3500 | return error; |
| 3501 | } |
| 3502 | EXPORT_SYMBOL(vfs_mkdir); |
| 3503 | |
| 3504 | SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode) |
| 3505 | { |
| 3506 | struct dentry *dentry; |
| 3507 | struct path path; |
| 3508 | int error; |
| 3509 | unsigned int lookup_flags = LOOKUP_DIRECTORY; |
| 3510 | |
| 3511 | retry: |
| 3512 | dentry = user_path_create(dfd, pathname, &path, lookup_flags); |
| 3513 | if (IS_ERR(dentry)) |
| 3514 | return PTR_ERR(dentry); |
| 3515 | |
| 3516 | if (!IS_POSIXACL(path.dentry->d_inode)) |
| 3517 | mode &= ~current_umask(); |
| 3518 | error = security_path_mkdir(&path, dentry, mode); |
| 3519 | if (!error) |
| 3520 | error = vfs_mkdir(path.dentry->d_inode, dentry, mode); |
| 3521 | done_path_create(&path, dentry); |
| 3522 | if (retry_estale(error, lookup_flags)) { |
| 3523 | lookup_flags |= LOOKUP_REVAL; |
| 3524 | goto retry; |
| 3525 | } |
| 3526 | return error; |
| 3527 | } |
| 3528 | |
| 3529 | SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode) |
| 3530 | { |
| 3531 | return sys_mkdirat(AT_FDCWD, pathname, mode); |
| 3532 | } |
| 3533 | |
| 3534 | /* |
| 3535 | * The dentry_unhash() helper will try to drop the dentry early: we |
| 3536 | * should have a usage count of 1 if we're the only user of this |
| 3537 | * dentry, and if that is true (possibly after pruning the dcache), |
| 3538 | * then we drop the dentry now. |
| 3539 | * |
| 3540 | * A low-level filesystem can, if it choses, legally |
| 3541 | * do a |
| 3542 | * |
| 3543 | * if (!d_unhashed(dentry)) |
| 3544 | * return -EBUSY; |
| 3545 | * |
| 3546 | * if it cannot handle the case of removing a directory |
| 3547 | * that is still in use by something else.. |
| 3548 | */ |
| 3549 | void dentry_unhash(struct dentry *dentry) |
| 3550 | { |
| 3551 | shrink_dcache_parent(dentry); |
| 3552 | spin_lock(&dentry->d_lock); |
| 3553 | if (dentry->d_lockref.count == 1) |
| 3554 | __d_drop(dentry); |
| 3555 | spin_unlock(&dentry->d_lock); |
| 3556 | } |
| 3557 | EXPORT_SYMBOL(dentry_unhash); |
| 3558 | |
| 3559 | int vfs_rmdir(struct inode *dir, struct dentry *dentry) |
| 3560 | { |
| 3561 | int error = may_delete(dir, dentry, 1); |
| 3562 | |
| 3563 | if (error) |
| 3564 | return error; |
| 3565 | |
| 3566 | if (!dir->i_op->rmdir) |
| 3567 | return -EPERM; |
| 3568 | |
| 3569 | dget(dentry); |
| 3570 | mutex_lock(&dentry->d_inode->i_mutex); |
| 3571 | |
| 3572 | error = -EBUSY; |
| 3573 | if (is_local_mountpoint(dentry)) |
| 3574 | goto out; |
| 3575 | |
| 3576 | error = security_inode_rmdir(dir, dentry); |
| 3577 | if (error) |
| 3578 | goto out; |
| 3579 | |
| 3580 | shrink_dcache_parent(dentry); |
| 3581 | error = dir->i_op->rmdir(dir, dentry); |
| 3582 | if (error) |
| 3583 | goto out; |
| 3584 | |
| 3585 | dentry->d_inode->i_flags |= S_DEAD; |
| 3586 | dont_mount(dentry); |
| 3587 | detach_mounts(dentry); |
| 3588 | |
| 3589 | out: |
| 3590 | mutex_unlock(&dentry->d_inode->i_mutex); |
| 3591 | dput(dentry); |
| 3592 | if (!error) |
| 3593 | d_delete(dentry); |
| 3594 | return error; |
| 3595 | } |
| 3596 | EXPORT_SYMBOL(vfs_rmdir); |
| 3597 | |
| 3598 | static long do_rmdir(int dfd, const char __user *pathname) |
| 3599 | { |
| 3600 | int error = 0; |
| 3601 | struct filename *name; |
| 3602 | struct dentry *dentry; |
| 3603 | struct nameidata nd; |
| 3604 | unsigned int lookup_flags = 0; |
| 3605 | retry: |
| 3606 | name = user_path_parent(dfd, pathname, &nd, lookup_flags); |
| 3607 | if (IS_ERR(name)) |
| 3608 | return PTR_ERR(name); |
| 3609 | |
| 3610 | switch(nd.last_type) { |
| 3611 | case LAST_DOTDOT: |
| 3612 | error = -ENOTEMPTY; |
| 3613 | goto exit1; |
| 3614 | case LAST_DOT: |
| 3615 | error = -EINVAL; |
| 3616 | goto exit1; |
| 3617 | case LAST_ROOT: |
| 3618 | error = -EBUSY; |
| 3619 | goto exit1; |
| 3620 | } |
| 3621 | |
| 3622 | nd.flags &= ~LOOKUP_PARENT; |
| 3623 | error = mnt_want_write(nd.path.mnt); |
| 3624 | if (error) |
| 3625 | goto exit1; |
| 3626 | |
| 3627 | mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); |
| 3628 | dentry = lookup_hash(&nd); |
| 3629 | error = PTR_ERR(dentry); |
| 3630 | if (IS_ERR(dentry)) |
| 3631 | goto exit2; |
| 3632 | if (!dentry->d_inode) { |
| 3633 | error = -ENOENT; |
| 3634 | goto exit3; |
| 3635 | } |
| 3636 | error = security_path_rmdir(&nd.path, dentry); |
| 3637 | if (error) |
| 3638 | goto exit3; |
| 3639 | error = vfs_rmdir(nd.path.dentry->d_inode, dentry); |
| 3640 | exit3: |
| 3641 | dput(dentry); |
| 3642 | exit2: |
| 3643 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); |
| 3644 | mnt_drop_write(nd.path.mnt); |
| 3645 | exit1: |
| 3646 | path_put(&nd.path); |
| 3647 | putname(name); |
| 3648 | if (retry_estale(error, lookup_flags)) { |
| 3649 | lookup_flags |= LOOKUP_REVAL; |
| 3650 | goto retry; |
| 3651 | } |
| 3652 | return error; |
| 3653 | } |
| 3654 | |
| 3655 | SYSCALL_DEFINE1(rmdir, const char __user *, pathname) |
| 3656 | { |
| 3657 | return do_rmdir(AT_FDCWD, pathname); |
| 3658 | } |
| 3659 | |
| 3660 | /** |
| 3661 | * vfs_unlink - unlink a filesystem object |
| 3662 | * @dir: parent directory |
| 3663 | * @dentry: victim |
| 3664 | * @delegated_inode: returns victim inode, if the inode is delegated. |
| 3665 | * |
| 3666 | * The caller must hold dir->i_mutex. |
| 3667 | * |
| 3668 | * If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and |
| 3669 | * return a reference to the inode in delegated_inode. The caller |
| 3670 | * should then break the delegation on that inode and retry. Because |
| 3671 | * breaking a delegation may take a long time, the caller should drop |
| 3672 | * dir->i_mutex before doing so. |
| 3673 | * |
| 3674 | * Alternatively, a caller may pass NULL for delegated_inode. This may |
| 3675 | * be appropriate for callers that expect the underlying filesystem not |
| 3676 | * to be NFS exported. |
| 3677 | */ |
| 3678 | int vfs_unlink(struct inode *dir, struct dentry *dentry, struct inode **delegated_inode) |
| 3679 | { |
| 3680 | struct inode *target = dentry->d_inode; |
| 3681 | int error = may_delete(dir, dentry, 0); |
| 3682 | |
| 3683 | if (error) |
| 3684 | return error; |
| 3685 | |
| 3686 | if (!dir->i_op->unlink) |
| 3687 | return -EPERM; |
| 3688 | |
| 3689 | mutex_lock(&target->i_mutex); |
| 3690 | if (is_local_mountpoint(dentry)) |
| 3691 | error = -EBUSY; |
| 3692 | else { |
| 3693 | error = security_inode_unlink(dir, dentry); |
| 3694 | if (!error) { |
| 3695 | error = try_break_deleg(target, delegated_inode); |
| 3696 | if (error) |
| 3697 | goto out; |
| 3698 | error = dir->i_op->unlink(dir, dentry); |
| 3699 | if (!error) { |
| 3700 | dont_mount(dentry); |
| 3701 | detach_mounts(dentry); |
| 3702 | } |
| 3703 | } |
| 3704 | } |
| 3705 | out: |
| 3706 | mutex_unlock(&target->i_mutex); |
| 3707 | |
| 3708 | /* We don't d_delete() NFS sillyrenamed files--they still exist. */ |
| 3709 | if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) { |
| 3710 | fsnotify_link_count(target); |
| 3711 | d_delete(dentry); |
| 3712 | } |
| 3713 | |
| 3714 | return error; |
| 3715 | } |
| 3716 | EXPORT_SYMBOL(vfs_unlink); |
| 3717 | |
| 3718 | /* |
| 3719 | * Make sure that the actual truncation of the file will occur outside its |
| 3720 | * directory's i_mutex. Truncate can take a long time if there is a lot of |
| 3721 | * writeout happening, and we don't want to prevent access to the directory |
| 3722 | * while waiting on the I/O. |
| 3723 | */ |
| 3724 | static long do_unlinkat(int dfd, const char __user *pathname) |
| 3725 | { |
| 3726 | int error; |
| 3727 | struct filename *name; |
| 3728 | struct dentry *dentry; |
| 3729 | struct nameidata nd; |
| 3730 | struct inode *inode = NULL; |
| 3731 | struct inode *delegated_inode = NULL; |
| 3732 | unsigned int lookup_flags = 0; |
| 3733 | retry: |
| 3734 | name = user_path_parent(dfd, pathname, &nd, lookup_flags); |
| 3735 | if (IS_ERR(name)) |
| 3736 | return PTR_ERR(name); |
| 3737 | |
| 3738 | error = -EISDIR; |
| 3739 | if (nd.last_type != LAST_NORM) |
| 3740 | goto exit1; |
| 3741 | |
| 3742 | nd.flags &= ~LOOKUP_PARENT; |
| 3743 | error = mnt_want_write(nd.path.mnt); |
| 3744 | if (error) |
| 3745 | goto exit1; |
| 3746 | retry_deleg: |
| 3747 | mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); |
| 3748 | dentry = lookup_hash(&nd); |
| 3749 | error = PTR_ERR(dentry); |
| 3750 | if (!IS_ERR(dentry)) { |
| 3751 | /* Why not before? Because we want correct error value */ |
| 3752 | if (nd.last.name[nd.last.len]) |
| 3753 | goto slashes; |
| 3754 | inode = dentry->d_inode; |
| 3755 | if (d_is_negative(dentry)) |
| 3756 | goto slashes; |
| 3757 | ihold(inode); |
| 3758 | error = security_path_unlink(&nd.path, dentry); |
| 3759 | if (error) |
| 3760 | goto exit2; |
| 3761 | error = vfs_unlink(nd.path.dentry->d_inode, dentry, &delegated_inode); |
| 3762 | exit2: |
| 3763 | dput(dentry); |
| 3764 | } |
| 3765 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); |
| 3766 | if (inode) |
| 3767 | iput(inode); /* truncate the inode here */ |
| 3768 | inode = NULL; |
| 3769 | if (delegated_inode) { |
| 3770 | error = break_deleg_wait(&delegated_inode); |
| 3771 | if (!error) |
| 3772 | goto retry_deleg; |
| 3773 | } |
| 3774 | mnt_drop_write(nd.path.mnt); |
| 3775 | exit1: |
| 3776 | path_put(&nd.path); |
| 3777 | putname(name); |
| 3778 | if (retry_estale(error, lookup_flags)) { |
| 3779 | lookup_flags |= LOOKUP_REVAL; |
| 3780 | inode = NULL; |
| 3781 | goto retry; |
| 3782 | } |
| 3783 | return error; |
| 3784 | |
| 3785 | slashes: |
| 3786 | if (d_is_negative(dentry)) |
| 3787 | error = -ENOENT; |
| 3788 | else if (d_is_dir(dentry)) |
| 3789 | error = -EISDIR; |
| 3790 | else |
| 3791 | error = -ENOTDIR; |
| 3792 | goto exit2; |
| 3793 | } |
| 3794 | |
| 3795 | SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag) |
| 3796 | { |
| 3797 | if ((flag & ~AT_REMOVEDIR) != 0) |
| 3798 | return -EINVAL; |
| 3799 | |
| 3800 | if (flag & AT_REMOVEDIR) |
| 3801 | return do_rmdir(dfd, pathname); |
| 3802 | |
| 3803 | return do_unlinkat(dfd, pathname); |
| 3804 | } |
| 3805 | |
| 3806 | SYSCALL_DEFINE1(unlink, const char __user *, pathname) |
| 3807 | { |
| 3808 | return do_unlinkat(AT_FDCWD, pathname); |
| 3809 | } |
| 3810 | |
| 3811 | int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname) |
| 3812 | { |
| 3813 | int error = may_create(dir, dentry); |
| 3814 | |
| 3815 | if (error) |
| 3816 | return error; |
| 3817 | |
| 3818 | if (!dir->i_op->symlink) |
| 3819 | return -EPERM; |
| 3820 | |
| 3821 | error = security_inode_symlink(dir, dentry, oldname); |
| 3822 | if (error) |
| 3823 | return error; |
| 3824 | |
| 3825 | error = dir->i_op->symlink(dir, dentry, oldname); |
| 3826 | if (!error) |
| 3827 | fsnotify_create(dir, dentry); |
| 3828 | return error; |
| 3829 | } |
| 3830 | EXPORT_SYMBOL(vfs_symlink); |
| 3831 | |
| 3832 | SYSCALL_DEFINE3(symlinkat, const char __user *, oldname, |
| 3833 | int, newdfd, const char __user *, newname) |
| 3834 | { |
| 3835 | int error; |
| 3836 | struct filename *from; |
| 3837 | struct dentry *dentry; |
| 3838 | struct path path; |
| 3839 | unsigned int lookup_flags = 0; |
| 3840 | |
| 3841 | from = getname(oldname); |
| 3842 | if (IS_ERR(from)) |
| 3843 | return PTR_ERR(from); |
| 3844 | retry: |
| 3845 | dentry = user_path_create(newdfd, newname, &path, lookup_flags); |
| 3846 | error = PTR_ERR(dentry); |
| 3847 | if (IS_ERR(dentry)) |
| 3848 | goto out_putname; |
| 3849 | |
| 3850 | error = security_path_symlink(&path, dentry, from->name); |
| 3851 | if (!error) |
| 3852 | error = vfs_symlink(path.dentry->d_inode, dentry, from->name); |
| 3853 | done_path_create(&path, dentry); |
| 3854 | if (retry_estale(error, lookup_flags)) { |
| 3855 | lookup_flags |= LOOKUP_REVAL; |
| 3856 | goto retry; |
| 3857 | } |
| 3858 | out_putname: |
| 3859 | putname(from); |
| 3860 | return error; |
| 3861 | } |
| 3862 | |
| 3863 | SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname) |
| 3864 | { |
| 3865 | return sys_symlinkat(oldname, AT_FDCWD, newname); |
| 3866 | } |
| 3867 | |
| 3868 | /** |
| 3869 | * vfs_link - create a new link |
| 3870 | * @old_dentry: object to be linked |
| 3871 | * @dir: new parent |
| 3872 | * @new_dentry: where to create the new link |
| 3873 | * @delegated_inode: returns inode needing a delegation break |
| 3874 | * |
| 3875 | * The caller must hold dir->i_mutex |
| 3876 | * |
| 3877 | * If vfs_link discovers a delegation on the to-be-linked file in need |
| 3878 | * of breaking, it will return -EWOULDBLOCK and return a reference to the |
| 3879 | * inode in delegated_inode. The caller should then break the delegation |
| 3880 | * and retry. Because breaking a delegation may take a long time, the |
| 3881 | * caller should drop the i_mutex before doing so. |
| 3882 | * |
| 3883 | * Alternatively, a caller may pass NULL for delegated_inode. This may |
| 3884 | * be appropriate for callers that expect the underlying filesystem not |
| 3885 | * to be NFS exported. |
| 3886 | */ |
| 3887 | int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry, struct inode **delegated_inode) |
| 3888 | { |
| 3889 | struct inode *inode = old_dentry->d_inode; |
| 3890 | unsigned max_links = dir->i_sb->s_max_links; |
| 3891 | int error; |
| 3892 | |
| 3893 | if (!inode) |
| 3894 | return -ENOENT; |
| 3895 | |
| 3896 | error = may_create(dir, new_dentry); |
| 3897 | if (error) |
| 3898 | return error; |
| 3899 | |
| 3900 | if (dir->i_sb != inode->i_sb) |
| 3901 | return -EXDEV; |
| 3902 | |
| 3903 | /* |
| 3904 | * A link to an append-only or immutable file cannot be created. |
| 3905 | */ |
| 3906 | if (IS_APPEND(inode) || IS_IMMUTABLE(inode)) |
| 3907 | return -EPERM; |
| 3908 | if (!dir->i_op->link) |
| 3909 | return -EPERM; |
| 3910 | if (S_ISDIR(inode->i_mode)) |
| 3911 | return -EPERM; |
| 3912 | |
| 3913 | error = security_inode_link(old_dentry, dir, new_dentry); |
| 3914 | if (error) |
| 3915 | return error; |
| 3916 | |
| 3917 | mutex_lock(&inode->i_mutex); |
| 3918 | /* Make sure we don't allow creating hardlink to an unlinked file */ |
| 3919 | if (inode->i_nlink == 0 && !(inode->i_state & I_LINKABLE)) |
| 3920 | error = -ENOENT; |
| 3921 | else if (max_links && inode->i_nlink >= max_links) |
| 3922 | error = -EMLINK; |
| 3923 | else { |
| 3924 | error = try_break_deleg(inode, delegated_inode); |
| 3925 | if (!error) |
| 3926 | error = dir->i_op->link(old_dentry, dir, new_dentry); |
| 3927 | } |
| 3928 | |
| 3929 | if (!error && (inode->i_state & I_LINKABLE)) { |
| 3930 | spin_lock(&inode->i_lock); |
| 3931 | inode->i_state &= ~I_LINKABLE; |
| 3932 | spin_unlock(&inode->i_lock); |
| 3933 | } |
| 3934 | mutex_unlock(&inode->i_mutex); |
| 3935 | if (!error) |
| 3936 | fsnotify_link(dir, inode, new_dentry); |
| 3937 | return error; |
| 3938 | } |
| 3939 | EXPORT_SYMBOL(vfs_link); |
| 3940 | |
| 3941 | /* |
| 3942 | * Hardlinks are often used in delicate situations. We avoid |
| 3943 | * security-related surprises by not following symlinks on the |
| 3944 | * newname. --KAB |
| 3945 | * |
| 3946 | * We don't follow them on the oldname either to be compatible |
| 3947 | * with linux 2.0, and to avoid hard-linking to directories |
| 3948 | * and other special files. --ADM |
| 3949 | */ |
| 3950 | SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname, |
| 3951 | int, newdfd, const char __user *, newname, int, flags) |
| 3952 | { |
| 3953 | struct dentry *new_dentry; |
| 3954 | struct path old_path, new_path; |
| 3955 | struct inode *delegated_inode = NULL; |
| 3956 | int how = 0; |
| 3957 | int error; |
| 3958 | |
| 3959 | if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0) |
| 3960 | return -EINVAL; |
| 3961 | /* |
| 3962 | * To use null names we require CAP_DAC_READ_SEARCH |
| 3963 | * This ensures that not everyone will be able to create |
| 3964 | * handlink using the passed filedescriptor. |
| 3965 | */ |
| 3966 | if (flags & AT_EMPTY_PATH) { |
| 3967 | if (!capable(CAP_DAC_READ_SEARCH)) |
| 3968 | return -ENOENT; |
| 3969 | how = LOOKUP_EMPTY; |
| 3970 | } |
| 3971 | |
| 3972 | if (flags & AT_SYMLINK_FOLLOW) |
| 3973 | how |= LOOKUP_FOLLOW; |
| 3974 | retry: |
| 3975 | error = user_path_at(olddfd, oldname, how, &old_path); |
| 3976 | if (error) |
| 3977 | return error; |
| 3978 | |
| 3979 | new_dentry = user_path_create(newdfd, newname, &new_path, |
| 3980 | (how & LOOKUP_REVAL)); |
| 3981 | error = PTR_ERR(new_dentry); |
| 3982 | if (IS_ERR(new_dentry)) |
| 3983 | goto out; |
| 3984 | |
| 3985 | error = -EXDEV; |
| 3986 | if (old_path.mnt != new_path.mnt) |
| 3987 | goto out_dput; |
| 3988 | error = may_linkat(&old_path); |
| 3989 | if (unlikely(error)) |
| 3990 | goto out_dput; |
| 3991 | error = security_path_link(old_path.dentry, &new_path, new_dentry); |
| 3992 | if (error) |
| 3993 | goto out_dput; |
| 3994 | error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry, &delegated_inode); |
| 3995 | out_dput: |
| 3996 | done_path_create(&new_path, new_dentry); |
| 3997 | if (delegated_inode) { |
| 3998 | error = break_deleg_wait(&delegated_inode); |
| 3999 | if (!error) { |
| 4000 | path_put(&old_path); |
| 4001 | goto retry; |
| 4002 | } |
| 4003 | } |
| 4004 | if (retry_estale(error, how)) { |
| 4005 | path_put(&old_path); |
| 4006 | how |= LOOKUP_REVAL; |
| 4007 | goto retry; |
| 4008 | } |
| 4009 | out: |
| 4010 | path_put(&old_path); |
| 4011 | |
| 4012 | return error; |
| 4013 | } |
| 4014 | |
| 4015 | SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname) |
| 4016 | { |
| 4017 | return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0); |
| 4018 | } |
| 4019 | |
| 4020 | /** |
| 4021 | * vfs_rename - rename a filesystem object |
| 4022 | * @old_dir: parent of source |
| 4023 | * @old_dentry: source |
| 4024 | * @new_dir: parent of destination |
| 4025 | * @new_dentry: destination |
| 4026 | * @delegated_inode: returns an inode needing a delegation break |
| 4027 | * @flags: rename flags |
| 4028 | * |
| 4029 | * The caller must hold multiple mutexes--see lock_rename()). |
| 4030 | * |
| 4031 | * If vfs_rename discovers a delegation in need of breaking at either |
| 4032 | * the source or destination, it will return -EWOULDBLOCK and return a |
| 4033 | * reference to the inode in delegated_inode. The caller should then |
| 4034 | * break the delegation and retry. Because breaking a delegation may |
| 4035 | * take a long time, the caller should drop all locks before doing |
| 4036 | * so. |
| 4037 | * |
| 4038 | * Alternatively, a caller may pass NULL for delegated_inode. This may |
| 4039 | * be appropriate for callers that expect the underlying filesystem not |
| 4040 | * to be NFS exported. |
| 4041 | * |
| 4042 | * The worst of all namespace operations - renaming directory. "Perverted" |
| 4043 | * doesn't even start to describe it. Somebody in UCB had a heck of a trip... |
| 4044 | * Problems: |
| 4045 | * a) we can get into loop creation. |
| 4046 | * b) race potential - two innocent renames can create a loop together. |
| 4047 | * That's where 4.4 screws up. Current fix: serialization on |
| 4048 | * sb->s_vfs_rename_mutex. We might be more accurate, but that's another |
| 4049 | * story. |
| 4050 | * c) we have to lock _four_ objects - parents and victim (if it exists), |
| 4051 | * and source (if it is not a directory). |
| 4052 | * And that - after we got ->i_mutex on parents (until then we don't know |
| 4053 | * whether the target exists). Solution: try to be smart with locking |
| 4054 | * order for inodes. We rely on the fact that tree topology may change |
| 4055 | * only under ->s_vfs_rename_mutex _and_ that parent of the object we |
| 4056 | * move will be locked. Thus we can rank directories by the tree |
| 4057 | * (ancestors first) and rank all non-directories after them. |
| 4058 | * That works since everybody except rename does "lock parent, lookup, |
| 4059 | * lock child" and rename is under ->s_vfs_rename_mutex. |
| 4060 | * HOWEVER, it relies on the assumption that any object with ->lookup() |
| 4061 | * has no more than 1 dentry. If "hybrid" objects will ever appear, |
| 4062 | * we'd better make sure that there's no link(2) for them. |
| 4063 | * d) conversion from fhandle to dentry may come in the wrong moment - when |
| 4064 | * we are removing the target. Solution: we will have to grab ->i_mutex |
| 4065 | * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on |
| 4066 | * ->i_mutex on parents, which works but leads to some truly excessive |
| 4067 | * locking]. |
| 4068 | */ |
| 4069 | int vfs_rename(struct inode *old_dir, struct dentry *old_dentry, |
| 4070 | struct inode *new_dir, struct dentry *new_dentry, |
| 4071 | struct inode **delegated_inode, unsigned int flags) |
| 4072 | { |
| 4073 | int error; |
| 4074 | bool is_dir = d_is_dir(old_dentry); |
| 4075 | const unsigned char *old_name; |
| 4076 | struct inode *source = old_dentry->d_inode; |
| 4077 | struct inode *target = new_dentry->d_inode; |
| 4078 | bool new_is_dir = false; |
| 4079 | unsigned max_links = new_dir->i_sb->s_max_links; |
| 4080 | |
| 4081 | if (source == target) |
| 4082 | return 0; |
| 4083 | |
| 4084 | error = may_delete(old_dir, old_dentry, is_dir); |
| 4085 | if (error) |
| 4086 | return error; |
| 4087 | |
| 4088 | if (!target) { |
| 4089 | error = may_create(new_dir, new_dentry); |
| 4090 | } else { |
| 4091 | new_is_dir = d_is_dir(new_dentry); |
| 4092 | |
| 4093 | if (!(flags & RENAME_EXCHANGE)) |
| 4094 | error = may_delete(new_dir, new_dentry, is_dir); |
| 4095 | else |
| 4096 | error = may_delete(new_dir, new_dentry, new_is_dir); |
| 4097 | } |
| 4098 | if (error) |
| 4099 | return error; |
| 4100 | |
| 4101 | if (!old_dir->i_op->rename && !old_dir->i_op->rename2) |
| 4102 | return -EPERM; |
| 4103 | |
| 4104 | if (flags && !old_dir->i_op->rename2) |
| 4105 | return -EINVAL; |
| 4106 | |
| 4107 | /* |
| 4108 | * If we are going to change the parent - check write permissions, |
| 4109 | * we'll need to flip '..'. |
| 4110 | */ |
| 4111 | if (new_dir != old_dir) { |
| 4112 | if (is_dir) { |
| 4113 | error = inode_permission(source, MAY_WRITE); |
| 4114 | if (error) |
| 4115 | return error; |
| 4116 | } |
| 4117 | if ((flags & RENAME_EXCHANGE) && new_is_dir) { |
| 4118 | error = inode_permission(target, MAY_WRITE); |
| 4119 | if (error) |
| 4120 | return error; |
| 4121 | } |
| 4122 | } |
| 4123 | |
| 4124 | error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry, |
| 4125 | flags); |
| 4126 | if (error) |
| 4127 | return error; |
| 4128 | |
| 4129 | old_name = fsnotify_oldname_init(old_dentry->d_name.name); |
| 4130 | dget(new_dentry); |
| 4131 | if (!is_dir || (flags & RENAME_EXCHANGE)) |
| 4132 | lock_two_nondirectories(source, target); |
| 4133 | else if (target) |
| 4134 | mutex_lock(&target->i_mutex); |
| 4135 | |
| 4136 | error = -EBUSY; |
| 4137 | if (is_local_mountpoint(old_dentry) || is_local_mountpoint(new_dentry)) |
| 4138 | goto out; |
| 4139 | |
| 4140 | if (max_links && new_dir != old_dir) { |
| 4141 | error = -EMLINK; |
| 4142 | if (is_dir && !new_is_dir && new_dir->i_nlink >= max_links) |
| 4143 | goto out; |
| 4144 | if ((flags & RENAME_EXCHANGE) && !is_dir && new_is_dir && |
| 4145 | old_dir->i_nlink >= max_links) |
| 4146 | goto out; |
| 4147 | } |
| 4148 | if (is_dir && !(flags & RENAME_EXCHANGE) && target) |
| 4149 | shrink_dcache_parent(new_dentry); |
| 4150 | if (!is_dir) { |
| 4151 | error = try_break_deleg(source, delegated_inode); |
| 4152 | if (error) |
| 4153 | goto out; |
| 4154 | } |
| 4155 | if (target && !new_is_dir) { |
| 4156 | error = try_break_deleg(target, delegated_inode); |
| 4157 | if (error) |
| 4158 | goto out; |
| 4159 | } |
| 4160 | if (!old_dir->i_op->rename2) { |
| 4161 | error = old_dir->i_op->rename(old_dir, old_dentry, |
| 4162 | new_dir, new_dentry); |
| 4163 | } else { |
| 4164 | WARN_ON(old_dir->i_op->rename != NULL); |
| 4165 | error = old_dir->i_op->rename2(old_dir, old_dentry, |
| 4166 | new_dir, new_dentry, flags); |
| 4167 | } |
| 4168 | if (error) |
| 4169 | goto out; |
| 4170 | |
| 4171 | if (!(flags & RENAME_EXCHANGE) && target) { |
| 4172 | if (is_dir) |
| 4173 | target->i_flags |= S_DEAD; |
| 4174 | dont_mount(new_dentry); |
| 4175 | detach_mounts(new_dentry); |
| 4176 | } |
| 4177 | if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) { |
| 4178 | if (!(flags & RENAME_EXCHANGE)) |
| 4179 | d_move(old_dentry, new_dentry); |
| 4180 | else |
| 4181 | d_exchange(old_dentry, new_dentry); |
| 4182 | } |
| 4183 | out: |
| 4184 | if (!is_dir || (flags & RENAME_EXCHANGE)) |
| 4185 | unlock_two_nondirectories(source, target); |
| 4186 | else if (target) |
| 4187 | mutex_unlock(&target->i_mutex); |
| 4188 | dput(new_dentry); |
| 4189 | if (!error) { |
| 4190 | fsnotify_move(old_dir, new_dir, old_name, is_dir, |
| 4191 | !(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry); |
| 4192 | if (flags & RENAME_EXCHANGE) { |
| 4193 | fsnotify_move(new_dir, old_dir, old_dentry->d_name.name, |
| 4194 | new_is_dir, NULL, new_dentry); |
| 4195 | } |
| 4196 | } |
| 4197 | fsnotify_oldname_free(old_name); |
| 4198 | |
| 4199 | return error; |
| 4200 | } |
| 4201 | EXPORT_SYMBOL(vfs_rename); |
| 4202 | |
| 4203 | SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname, |
| 4204 | int, newdfd, const char __user *, newname, unsigned int, flags) |
| 4205 | { |
| 4206 | struct dentry *old_dir, *new_dir; |
| 4207 | struct dentry *old_dentry, *new_dentry; |
| 4208 | struct dentry *trap; |
| 4209 | struct nameidata oldnd, newnd; |
| 4210 | struct inode *delegated_inode = NULL; |
| 4211 | struct filename *from; |
| 4212 | struct filename *to; |
| 4213 | unsigned int lookup_flags = 0; |
| 4214 | bool should_retry = false; |
| 4215 | int error; |
| 4216 | |
| 4217 | if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT)) |
| 4218 | return -EINVAL; |
| 4219 | |
| 4220 | if ((flags & (RENAME_NOREPLACE | RENAME_WHITEOUT)) && |
| 4221 | (flags & RENAME_EXCHANGE)) |
| 4222 | return -EINVAL; |
| 4223 | |
| 4224 | if ((flags & RENAME_WHITEOUT) && !capable(CAP_MKNOD)) |
| 4225 | return -EPERM; |
| 4226 | |
| 4227 | retry: |
| 4228 | from = user_path_parent(olddfd, oldname, &oldnd, lookup_flags); |
| 4229 | if (IS_ERR(from)) { |
| 4230 | error = PTR_ERR(from); |
| 4231 | goto exit; |
| 4232 | } |
| 4233 | |
| 4234 | to = user_path_parent(newdfd, newname, &newnd, lookup_flags); |
| 4235 | if (IS_ERR(to)) { |
| 4236 | error = PTR_ERR(to); |
| 4237 | goto exit1; |
| 4238 | } |
| 4239 | |
| 4240 | error = -EXDEV; |
| 4241 | if (oldnd.path.mnt != newnd.path.mnt) |
| 4242 | goto exit2; |
| 4243 | |
| 4244 | old_dir = oldnd.path.dentry; |
| 4245 | error = -EBUSY; |
| 4246 | if (oldnd.last_type != LAST_NORM) |
| 4247 | goto exit2; |
| 4248 | |
| 4249 | new_dir = newnd.path.dentry; |
| 4250 | if (flags & RENAME_NOREPLACE) |
| 4251 | error = -EEXIST; |
| 4252 | if (newnd.last_type != LAST_NORM) |
| 4253 | goto exit2; |
| 4254 | |
| 4255 | error = mnt_want_write(oldnd.path.mnt); |
| 4256 | if (error) |
| 4257 | goto exit2; |
| 4258 | |
| 4259 | oldnd.flags &= ~LOOKUP_PARENT; |
| 4260 | newnd.flags &= ~LOOKUP_PARENT; |
| 4261 | if (!(flags & RENAME_EXCHANGE)) |
| 4262 | newnd.flags |= LOOKUP_RENAME_TARGET; |
| 4263 | |
| 4264 | retry_deleg: |
| 4265 | trap = lock_rename(new_dir, old_dir); |
| 4266 | |
| 4267 | old_dentry = lookup_hash(&oldnd); |
| 4268 | error = PTR_ERR(old_dentry); |
| 4269 | if (IS_ERR(old_dentry)) |
| 4270 | goto exit3; |
| 4271 | /* source must exist */ |
| 4272 | error = -ENOENT; |
| 4273 | if (d_is_negative(old_dentry)) |
| 4274 | goto exit4; |
| 4275 | new_dentry = lookup_hash(&newnd); |
| 4276 | error = PTR_ERR(new_dentry); |
| 4277 | if (IS_ERR(new_dentry)) |
| 4278 | goto exit4; |
| 4279 | error = -EEXIST; |
| 4280 | if ((flags & RENAME_NOREPLACE) && d_is_positive(new_dentry)) |
| 4281 | goto exit5; |
| 4282 | if (flags & RENAME_EXCHANGE) { |
| 4283 | error = -ENOENT; |
| 4284 | if (d_is_negative(new_dentry)) |
| 4285 | goto exit5; |
| 4286 | |
| 4287 | if (!d_is_dir(new_dentry)) { |
| 4288 | error = -ENOTDIR; |
| 4289 | if (newnd.last.name[newnd.last.len]) |
| 4290 | goto exit5; |
| 4291 | } |
| 4292 | } |
| 4293 | /* unless the source is a directory trailing slashes give -ENOTDIR */ |
| 4294 | if (!d_is_dir(old_dentry)) { |
| 4295 | error = -ENOTDIR; |
| 4296 | if (oldnd.last.name[oldnd.last.len]) |
| 4297 | goto exit5; |
| 4298 | if (!(flags & RENAME_EXCHANGE) && newnd.last.name[newnd.last.len]) |
| 4299 | goto exit5; |
| 4300 | } |
| 4301 | /* source should not be ancestor of target */ |
| 4302 | error = -EINVAL; |
| 4303 | if (old_dentry == trap) |
| 4304 | goto exit5; |
| 4305 | /* target should not be an ancestor of source */ |
| 4306 | if (!(flags & RENAME_EXCHANGE)) |
| 4307 | error = -ENOTEMPTY; |
| 4308 | if (new_dentry == trap) |
| 4309 | goto exit5; |
| 4310 | |
| 4311 | error = security_path_rename(&oldnd.path, old_dentry, |
| 4312 | &newnd.path, new_dentry, flags); |
| 4313 | if (error) |
| 4314 | goto exit5; |
| 4315 | error = vfs_rename(old_dir->d_inode, old_dentry, |
| 4316 | new_dir->d_inode, new_dentry, |
| 4317 | &delegated_inode, flags); |
| 4318 | exit5: |
| 4319 | dput(new_dentry); |
| 4320 | exit4: |
| 4321 | dput(old_dentry); |
| 4322 | exit3: |
| 4323 | unlock_rename(new_dir, old_dir); |
| 4324 | if (delegated_inode) { |
| 4325 | error = break_deleg_wait(&delegated_inode); |
| 4326 | if (!error) |
| 4327 | goto retry_deleg; |
| 4328 | } |
| 4329 | mnt_drop_write(oldnd.path.mnt); |
| 4330 | exit2: |
| 4331 | if (retry_estale(error, lookup_flags)) |
| 4332 | should_retry = true; |
| 4333 | path_put(&newnd.path); |
| 4334 | putname(to); |
| 4335 | exit1: |
| 4336 | path_put(&oldnd.path); |
| 4337 | putname(from); |
| 4338 | if (should_retry) { |
| 4339 | should_retry = false; |
| 4340 | lookup_flags |= LOOKUP_REVAL; |
| 4341 | goto retry; |
| 4342 | } |
| 4343 | exit: |
| 4344 | return error; |
| 4345 | } |
| 4346 | |
| 4347 | SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname, |
| 4348 | int, newdfd, const char __user *, newname) |
| 4349 | { |
| 4350 | return sys_renameat2(olddfd, oldname, newdfd, newname, 0); |
| 4351 | } |
| 4352 | |
| 4353 | SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname) |
| 4354 | { |
| 4355 | return sys_renameat2(AT_FDCWD, oldname, AT_FDCWD, newname, 0); |
| 4356 | } |
| 4357 | |
| 4358 | int vfs_whiteout(struct inode *dir, struct dentry *dentry) |
| 4359 | { |
| 4360 | int error = may_create(dir, dentry); |
| 4361 | if (error) |
| 4362 | return error; |
| 4363 | |
| 4364 | if (!dir->i_op->mknod) |
| 4365 | return -EPERM; |
| 4366 | |
| 4367 | return dir->i_op->mknod(dir, dentry, |
| 4368 | S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV); |
| 4369 | } |
| 4370 | EXPORT_SYMBOL(vfs_whiteout); |
| 4371 | |
| 4372 | int readlink_copy(char __user *buffer, int buflen, const char *link) |
| 4373 | { |
| 4374 | int len = PTR_ERR(link); |
| 4375 | if (IS_ERR(link)) |
| 4376 | goto out; |
| 4377 | |
| 4378 | len = strlen(link); |
| 4379 | if (len > (unsigned) buflen) |
| 4380 | len = buflen; |
| 4381 | if (copy_to_user(buffer, link, len)) |
| 4382 | len = -EFAULT; |
| 4383 | out: |
| 4384 | return len; |
| 4385 | } |
| 4386 | EXPORT_SYMBOL(readlink_copy); |
| 4387 | |
| 4388 | /* |
| 4389 | * A helper for ->readlink(). This should be used *ONLY* for symlinks that |
| 4390 | * have ->follow_link() touching nd only in nd_set_link(). Using (or not |
| 4391 | * using) it for any given inode is up to filesystem. |
| 4392 | */ |
| 4393 | int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen) |
| 4394 | { |
| 4395 | struct nameidata nd; |
| 4396 | void *cookie; |
| 4397 | int res; |
| 4398 | |
| 4399 | nd.depth = 0; |
| 4400 | cookie = dentry->d_inode->i_op->follow_link(dentry, &nd); |
| 4401 | if (IS_ERR(cookie)) |
| 4402 | return PTR_ERR(cookie); |
| 4403 | |
| 4404 | res = readlink_copy(buffer, buflen, nd_get_link(&nd)); |
| 4405 | if (dentry->d_inode->i_op->put_link) |
| 4406 | dentry->d_inode->i_op->put_link(dentry, &nd, cookie); |
| 4407 | return res; |
| 4408 | } |
| 4409 | EXPORT_SYMBOL(generic_readlink); |
| 4410 | |
| 4411 | /* get the link contents into pagecache */ |
| 4412 | static char *page_getlink(struct dentry * dentry, struct page **ppage) |
| 4413 | { |
| 4414 | char *kaddr; |
| 4415 | struct page *page; |
| 4416 | struct address_space *mapping = dentry->d_inode->i_mapping; |
| 4417 | page = read_mapping_page(mapping, 0, NULL); |
| 4418 | if (IS_ERR(page)) |
| 4419 | return (char*)page; |
| 4420 | *ppage = page; |
| 4421 | kaddr = kmap(page); |
| 4422 | nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1); |
| 4423 | return kaddr; |
| 4424 | } |
| 4425 | |
| 4426 | int page_readlink(struct dentry *dentry, char __user *buffer, int buflen) |
| 4427 | { |
| 4428 | struct page *page = NULL; |
| 4429 | int res = readlink_copy(buffer, buflen, page_getlink(dentry, &page)); |
| 4430 | if (page) { |
| 4431 | kunmap(page); |
| 4432 | page_cache_release(page); |
| 4433 | } |
| 4434 | return res; |
| 4435 | } |
| 4436 | EXPORT_SYMBOL(page_readlink); |
| 4437 | |
| 4438 | void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd) |
| 4439 | { |
| 4440 | struct page *page = NULL; |
| 4441 | nd_set_link(nd, page_getlink(dentry, &page)); |
| 4442 | return page; |
| 4443 | } |
| 4444 | EXPORT_SYMBOL(page_follow_link_light); |
| 4445 | |
| 4446 | void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie) |
| 4447 | { |
| 4448 | struct page *page = cookie; |
| 4449 | |
| 4450 | if (page) { |
| 4451 | kunmap(page); |
| 4452 | page_cache_release(page); |
| 4453 | } |
| 4454 | } |
| 4455 | EXPORT_SYMBOL(page_put_link); |
| 4456 | |
| 4457 | /* |
| 4458 | * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS |
| 4459 | */ |
| 4460 | int __page_symlink(struct inode *inode, const char *symname, int len, int nofs) |
| 4461 | { |
| 4462 | struct address_space *mapping = inode->i_mapping; |
| 4463 | struct page *page; |
| 4464 | void *fsdata; |
| 4465 | int err; |
| 4466 | char *kaddr; |
| 4467 | unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE; |
| 4468 | if (nofs) |
| 4469 | flags |= AOP_FLAG_NOFS; |
| 4470 | |
| 4471 | retry: |
| 4472 | err = pagecache_write_begin(NULL, mapping, 0, len-1, |
| 4473 | flags, &page, &fsdata); |
| 4474 | if (err) |
| 4475 | goto fail; |
| 4476 | |
| 4477 | kaddr = kmap_atomic(page); |
| 4478 | memcpy(kaddr, symname, len-1); |
| 4479 | kunmap_atomic(kaddr); |
| 4480 | |
| 4481 | err = pagecache_write_end(NULL, mapping, 0, len-1, len-1, |
| 4482 | page, fsdata); |
| 4483 | if (err < 0) |
| 4484 | goto fail; |
| 4485 | if (err < len-1) |
| 4486 | goto retry; |
| 4487 | |
| 4488 | mark_inode_dirty(inode); |
| 4489 | return 0; |
| 4490 | fail: |
| 4491 | return err; |
| 4492 | } |
| 4493 | EXPORT_SYMBOL(__page_symlink); |
| 4494 | |
| 4495 | int page_symlink(struct inode *inode, const char *symname, int len) |
| 4496 | { |
| 4497 | return __page_symlink(inode, symname, len, |
| 4498 | !(mapping_gfp_mask(inode->i_mapping) & __GFP_FS)); |
| 4499 | } |
| 4500 | EXPORT_SYMBOL(page_symlink); |
| 4501 | |
| 4502 | const struct inode_operations page_symlink_inode_operations = { |
| 4503 | .readlink = generic_readlink, |
| 4504 | .follow_link = page_follow_link_light, |
| 4505 | .put_link = page_put_link, |
| 4506 | }; |
| 4507 | EXPORT_SYMBOL(page_symlink_inode_operations); |