| 1 | /* -*- linux-c -*- --------------------------------------------------------- * |
| 2 | * |
| 3 | * linux/fs/devpts/inode.c |
| 4 | * |
| 5 | * Copyright 1998-2004 H. Peter Anvin -- All Rights Reserved |
| 6 | * |
| 7 | * This file is part of the Linux kernel and is made available under |
| 8 | * the terms of the GNU General Public License, version 2, or at your |
| 9 | * option, any later version, incorporated herein by reference. |
| 10 | * |
| 11 | * ------------------------------------------------------------------------- */ |
| 12 | |
| 13 | #include <linux/module.h> |
| 14 | #include <linux/init.h> |
| 15 | #include <linux/fs.h> |
| 16 | #include <linux/sched.h> |
| 17 | #include <linux/namei.h> |
| 18 | #include <linux/slab.h> |
| 19 | #include <linux/mount.h> |
| 20 | #include <linux/tty.h> |
| 21 | #include <linux/mutex.h> |
| 22 | #include <linux/magic.h> |
| 23 | #include <linux/idr.h> |
| 24 | #include <linux/devpts_fs.h> |
| 25 | #include <linux/parser.h> |
| 26 | #include <linux/fsnotify.h> |
| 27 | #include <linux/seq_file.h> |
| 28 | |
| 29 | #define DEVPTS_DEFAULT_MODE 0600 |
| 30 | /* |
| 31 | * ptmx is a new node in /dev/pts and will be unused in legacy (single- |
| 32 | * instance) mode. To prevent surprises in user space, set permissions of |
| 33 | * ptmx to 0. Use 'chmod' or remount with '-o ptmxmode' to set meaningful |
| 34 | * permissions. |
| 35 | */ |
| 36 | #define DEVPTS_DEFAULT_PTMX_MODE 0000 |
| 37 | #define PTMX_MINOR 2 |
| 38 | |
| 39 | /* |
| 40 | * sysctl support for setting limits on the number of Unix98 ptys allocated. |
| 41 | * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly. |
| 42 | */ |
| 43 | static int pty_limit = NR_UNIX98_PTY_DEFAULT; |
| 44 | static int pty_reserve = NR_UNIX98_PTY_RESERVE; |
| 45 | static int pty_limit_min; |
| 46 | static int pty_limit_max = INT_MAX; |
| 47 | static int pty_count; |
| 48 | |
| 49 | static struct ctl_table pty_table[] = { |
| 50 | { |
| 51 | .procname = "max", |
| 52 | .maxlen = sizeof(int), |
| 53 | .mode = 0644, |
| 54 | .data = &pty_limit, |
| 55 | .proc_handler = proc_dointvec_minmax, |
| 56 | .extra1 = &pty_limit_min, |
| 57 | .extra2 = &pty_limit_max, |
| 58 | }, { |
| 59 | .procname = "reserve", |
| 60 | .maxlen = sizeof(int), |
| 61 | .mode = 0644, |
| 62 | .data = &pty_reserve, |
| 63 | .proc_handler = proc_dointvec_minmax, |
| 64 | .extra1 = &pty_limit_min, |
| 65 | .extra2 = &pty_limit_max, |
| 66 | }, { |
| 67 | .procname = "nr", |
| 68 | .maxlen = sizeof(int), |
| 69 | .mode = 0444, |
| 70 | .data = &pty_count, |
| 71 | .proc_handler = proc_dointvec, |
| 72 | }, |
| 73 | {} |
| 74 | }; |
| 75 | |
| 76 | static struct ctl_table pty_kern_table[] = { |
| 77 | { |
| 78 | .procname = "pty", |
| 79 | .mode = 0555, |
| 80 | .child = pty_table, |
| 81 | }, |
| 82 | {} |
| 83 | }; |
| 84 | |
| 85 | static struct ctl_table pty_root_table[] = { |
| 86 | { |
| 87 | .procname = "kernel", |
| 88 | .mode = 0555, |
| 89 | .child = pty_kern_table, |
| 90 | }, |
| 91 | {} |
| 92 | }; |
| 93 | |
| 94 | static DEFINE_MUTEX(allocated_ptys_lock); |
| 95 | |
| 96 | static struct vfsmount *devpts_mnt; |
| 97 | |
| 98 | struct pts_mount_opts { |
| 99 | int setuid; |
| 100 | int setgid; |
| 101 | kuid_t uid; |
| 102 | kgid_t gid; |
| 103 | umode_t mode; |
| 104 | umode_t ptmxmode; |
| 105 | int newinstance; |
| 106 | int max; |
| 107 | }; |
| 108 | |
| 109 | enum { |
| 110 | Opt_uid, Opt_gid, Opt_mode, Opt_ptmxmode, Opt_newinstance, Opt_max, |
| 111 | Opt_err |
| 112 | }; |
| 113 | |
| 114 | static const match_table_t tokens = { |
| 115 | {Opt_uid, "uid=%u"}, |
| 116 | {Opt_gid, "gid=%u"}, |
| 117 | {Opt_mode, "mode=%o"}, |
| 118 | #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES |
| 119 | {Opt_ptmxmode, "ptmxmode=%o"}, |
| 120 | {Opt_newinstance, "newinstance"}, |
| 121 | {Opt_max, "max=%d"}, |
| 122 | #endif |
| 123 | {Opt_err, NULL} |
| 124 | }; |
| 125 | |
| 126 | struct pts_fs_info { |
| 127 | struct ida allocated_ptys; |
| 128 | struct pts_mount_opts mount_opts; |
| 129 | struct dentry *ptmx_dentry; |
| 130 | }; |
| 131 | |
| 132 | static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb) |
| 133 | { |
| 134 | return sb->s_fs_info; |
| 135 | } |
| 136 | |
| 137 | static inline struct super_block *pts_sb_from_inode(struct inode *inode) |
| 138 | { |
| 139 | #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES |
| 140 | if (inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC) |
| 141 | return inode->i_sb; |
| 142 | #endif |
| 143 | return devpts_mnt->mnt_sb; |
| 144 | } |
| 145 | |
| 146 | #define PARSE_MOUNT 0 |
| 147 | #define PARSE_REMOUNT 1 |
| 148 | |
| 149 | /* |
| 150 | * parse_mount_options(): |
| 151 | * Set @opts to mount options specified in @data. If an option is not |
| 152 | * specified in @data, set it to its default value. The exception is |
| 153 | * 'newinstance' option which can only be set/cleared on a mount (i.e. |
| 154 | * cannot be changed during remount). |
| 155 | * |
| 156 | * Note: @data may be NULL (in which case all options are set to default). |
| 157 | */ |
| 158 | static int parse_mount_options(char *data, int op, struct pts_mount_opts *opts) |
| 159 | { |
| 160 | char *p; |
| 161 | kuid_t uid; |
| 162 | kgid_t gid; |
| 163 | |
| 164 | opts->setuid = 0; |
| 165 | opts->setgid = 0; |
| 166 | opts->uid = GLOBAL_ROOT_UID; |
| 167 | opts->gid = GLOBAL_ROOT_GID; |
| 168 | opts->mode = DEVPTS_DEFAULT_MODE; |
| 169 | opts->ptmxmode = DEVPTS_DEFAULT_PTMX_MODE; |
| 170 | opts->max = NR_UNIX98_PTY_MAX; |
| 171 | |
| 172 | /* newinstance makes sense only on initial mount */ |
| 173 | if (op == PARSE_MOUNT) |
| 174 | opts->newinstance = 0; |
| 175 | |
| 176 | while ((p = strsep(&data, ",")) != NULL) { |
| 177 | substring_t args[MAX_OPT_ARGS]; |
| 178 | int token; |
| 179 | int option; |
| 180 | |
| 181 | if (!*p) |
| 182 | continue; |
| 183 | |
| 184 | token = match_token(p, tokens, args); |
| 185 | switch (token) { |
| 186 | case Opt_uid: |
| 187 | if (match_int(&args[0], &option)) |
| 188 | return -EINVAL; |
| 189 | uid = make_kuid(current_user_ns(), option); |
| 190 | if (!uid_valid(uid)) |
| 191 | return -EINVAL; |
| 192 | opts->uid = uid; |
| 193 | opts->setuid = 1; |
| 194 | break; |
| 195 | case Opt_gid: |
| 196 | if (match_int(&args[0], &option)) |
| 197 | return -EINVAL; |
| 198 | gid = make_kgid(current_user_ns(), option); |
| 199 | if (!gid_valid(gid)) |
| 200 | return -EINVAL; |
| 201 | opts->gid = gid; |
| 202 | opts->setgid = 1; |
| 203 | break; |
| 204 | case Opt_mode: |
| 205 | if (match_octal(&args[0], &option)) |
| 206 | return -EINVAL; |
| 207 | opts->mode = option & S_IALLUGO; |
| 208 | break; |
| 209 | #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES |
| 210 | case Opt_ptmxmode: |
| 211 | if (match_octal(&args[0], &option)) |
| 212 | return -EINVAL; |
| 213 | opts->ptmxmode = option & S_IALLUGO; |
| 214 | break; |
| 215 | case Opt_newinstance: |
| 216 | /* newinstance makes sense only on initial mount */ |
| 217 | if (op == PARSE_MOUNT) |
| 218 | opts->newinstance = 1; |
| 219 | break; |
| 220 | case Opt_max: |
| 221 | if (match_int(&args[0], &option) || |
| 222 | option < 0 || option > NR_UNIX98_PTY_MAX) |
| 223 | return -EINVAL; |
| 224 | opts->max = option; |
| 225 | break; |
| 226 | #endif |
| 227 | default: |
| 228 | printk(KERN_ERR "devpts: called with bogus options\n"); |
| 229 | return -EINVAL; |
| 230 | } |
| 231 | } |
| 232 | |
| 233 | return 0; |
| 234 | } |
| 235 | |
| 236 | #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES |
| 237 | static int mknod_ptmx(struct super_block *sb) |
| 238 | { |
| 239 | int mode; |
| 240 | int rc = -ENOMEM; |
| 241 | struct dentry *dentry; |
| 242 | struct inode *inode; |
| 243 | struct dentry *root = sb->s_root; |
| 244 | struct pts_fs_info *fsi = DEVPTS_SB(sb); |
| 245 | struct pts_mount_opts *opts = &fsi->mount_opts; |
| 246 | kuid_t root_uid; |
| 247 | kgid_t root_gid; |
| 248 | |
| 249 | root_uid = make_kuid(current_user_ns(), 0); |
| 250 | root_gid = make_kgid(current_user_ns(), 0); |
| 251 | if (!uid_valid(root_uid) || !gid_valid(root_gid)) |
| 252 | return -EINVAL; |
| 253 | |
| 254 | mutex_lock(&root->d_inode->i_mutex); |
| 255 | |
| 256 | /* If we have already created ptmx node, return */ |
| 257 | if (fsi->ptmx_dentry) { |
| 258 | rc = 0; |
| 259 | goto out; |
| 260 | } |
| 261 | |
| 262 | dentry = d_alloc_name(root, "ptmx"); |
| 263 | if (!dentry) { |
| 264 | printk(KERN_NOTICE "Unable to alloc dentry for ptmx node\n"); |
| 265 | goto out; |
| 266 | } |
| 267 | |
| 268 | /* |
| 269 | * Create a new 'ptmx' node in this mount of devpts. |
| 270 | */ |
| 271 | inode = new_inode(sb); |
| 272 | if (!inode) { |
| 273 | printk(KERN_ERR "Unable to alloc inode for ptmx node\n"); |
| 274 | dput(dentry); |
| 275 | goto out; |
| 276 | } |
| 277 | |
| 278 | inode->i_ino = 2; |
| 279 | inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; |
| 280 | |
| 281 | mode = S_IFCHR|opts->ptmxmode; |
| 282 | init_special_inode(inode, mode, MKDEV(TTYAUX_MAJOR, 2)); |
| 283 | inode->i_uid = root_uid; |
| 284 | inode->i_gid = root_gid; |
| 285 | |
| 286 | d_add(dentry, inode); |
| 287 | |
| 288 | fsi->ptmx_dentry = dentry; |
| 289 | rc = 0; |
| 290 | out: |
| 291 | mutex_unlock(&root->d_inode->i_mutex); |
| 292 | return rc; |
| 293 | } |
| 294 | |
| 295 | static void update_ptmx_mode(struct pts_fs_info *fsi) |
| 296 | { |
| 297 | struct inode *inode; |
| 298 | if (fsi->ptmx_dentry) { |
| 299 | inode = fsi->ptmx_dentry->d_inode; |
| 300 | inode->i_mode = S_IFCHR|fsi->mount_opts.ptmxmode; |
| 301 | } |
| 302 | } |
| 303 | #else |
| 304 | static inline void update_ptmx_mode(struct pts_fs_info *fsi) |
| 305 | { |
| 306 | return; |
| 307 | } |
| 308 | #endif |
| 309 | |
| 310 | static int devpts_remount(struct super_block *sb, int *flags, char *data) |
| 311 | { |
| 312 | int err; |
| 313 | struct pts_fs_info *fsi = DEVPTS_SB(sb); |
| 314 | struct pts_mount_opts *opts = &fsi->mount_opts; |
| 315 | |
| 316 | err = parse_mount_options(data, PARSE_REMOUNT, opts); |
| 317 | |
| 318 | /* |
| 319 | * parse_mount_options() restores options to default values |
| 320 | * before parsing and may have changed ptmxmode. So, update the |
| 321 | * mode in the inode too. Bogus options don't fail the remount, |
| 322 | * so do this even on error return. |
| 323 | */ |
| 324 | update_ptmx_mode(fsi); |
| 325 | |
| 326 | return err; |
| 327 | } |
| 328 | |
| 329 | static int devpts_show_options(struct seq_file *seq, struct dentry *root) |
| 330 | { |
| 331 | struct pts_fs_info *fsi = DEVPTS_SB(root->d_sb); |
| 332 | struct pts_mount_opts *opts = &fsi->mount_opts; |
| 333 | |
| 334 | if (opts->setuid) |
| 335 | seq_printf(seq, ",uid=%u", from_kuid_munged(&init_user_ns, opts->uid)); |
| 336 | if (opts->setgid) |
| 337 | seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, opts->gid)); |
| 338 | seq_printf(seq, ",mode=%03o", opts->mode); |
| 339 | #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES |
| 340 | seq_printf(seq, ",ptmxmode=%03o", opts->ptmxmode); |
| 341 | if (opts->max < NR_UNIX98_PTY_MAX) |
| 342 | seq_printf(seq, ",max=%d", opts->max); |
| 343 | #endif |
| 344 | |
| 345 | return 0; |
| 346 | } |
| 347 | |
| 348 | static const struct super_operations devpts_sops = { |
| 349 | .statfs = simple_statfs, |
| 350 | .remount_fs = devpts_remount, |
| 351 | .show_options = devpts_show_options, |
| 352 | }; |
| 353 | |
| 354 | static void *new_pts_fs_info(void) |
| 355 | { |
| 356 | struct pts_fs_info *fsi; |
| 357 | |
| 358 | fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL); |
| 359 | if (!fsi) |
| 360 | return NULL; |
| 361 | |
| 362 | ida_init(&fsi->allocated_ptys); |
| 363 | fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE; |
| 364 | fsi->mount_opts.ptmxmode = DEVPTS_DEFAULT_PTMX_MODE; |
| 365 | |
| 366 | return fsi; |
| 367 | } |
| 368 | |
| 369 | static int |
| 370 | devpts_fill_super(struct super_block *s, void *data, int silent) |
| 371 | { |
| 372 | struct inode *inode; |
| 373 | |
| 374 | s->s_blocksize = 1024; |
| 375 | s->s_blocksize_bits = 10; |
| 376 | s->s_magic = DEVPTS_SUPER_MAGIC; |
| 377 | s->s_op = &devpts_sops; |
| 378 | s->s_time_gran = 1; |
| 379 | |
| 380 | s->s_fs_info = new_pts_fs_info(); |
| 381 | if (!s->s_fs_info) |
| 382 | goto fail; |
| 383 | |
| 384 | inode = new_inode(s); |
| 385 | if (!inode) |
| 386 | goto fail; |
| 387 | inode->i_ino = 1; |
| 388 | inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; |
| 389 | inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR; |
| 390 | inode->i_op = &simple_dir_inode_operations; |
| 391 | inode->i_fop = &simple_dir_operations; |
| 392 | set_nlink(inode, 2); |
| 393 | |
| 394 | s->s_root = d_make_root(inode); |
| 395 | if (s->s_root) |
| 396 | return 0; |
| 397 | |
| 398 | printk(KERN_ERR "devpts: get root dentry failed\n"); |
| 399 | |
| 400 | fail: |
| 401 | return -ENOMEM; |
| 402 | } |
| 403 | |
| 404 | #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES |
| 405 | static int compare_init_pts_sb(struct super_block *s, void *p) |
| 406 | { |
| 407 | if (devpts_mnt) |
| 408 | return devpts_mnt->mnt_sb == s; |
| 409 | return 0; |
| 410 | } |
| 411 | |
| 412 | /* |
| 413 | * devpts_mount() |
| 414 | * |
| 415 | * If the '-o newinstance' mount option was specified, mount a new |
| 416 | * (private) instance of devpts. PTYs created in this instance are |
| 417 | * independent of the PTYs in other devpts instances. |
| 418 | * |
| 419 | * If the '-o newinstance' option was not specified, mount/remount the |
| 420 | * initial kernel mount of devpts. This type of mount gives the |
| 421 | * legacy, single-instance semantics. |
| 422 | * |
| 423 | * The 'newinstance' option is needed to support multiple namespace |
| 424 | * semantics in devpts while preserving backward compatibility of the |
| 425 | * current 'single-namespace' semantics. i.e all mounts of devpts |
| 426 | * without the 'newinstance' mount option should bind to the initial |
| 427 | * kernel mount, like mount_single(). |
| 428 | * |
| 429 | * Mounts with 'newinstance' option create a new, private namespace. |
| 430 | * |
| 431 | * NOTE: |
| 432 | * |
| 433 | * For single-mount semantics, devpts cannot use mount_single(), |
| 434 | * because mount_single()/sget() find and use the super-block from |
| 435 | * the most recent mount of devpts. But that recent mount may be a |
| 436 | * 'newinstance' mount and mount_single() would pick the newinstance |
| 437 | * super-block instead of the initial super-block. |
| 438 | */ |
| 439 | static struct dentry *devpts_mount(struct file_system_type *fs_type, |
| 440 | int flags, const char *dev_name, void *data) |
| 441 | { |
| 442 | int error; |
| 443 | struct pts_mount_opts opts; |
| 444 | struct super_block *s; |
| 445 | |
| 446 | error = parse_mount_options(data, PARSE_MOUNT, &opts); |
| 447 | if (error) |
| 448 | return ERR_PTR(error); |
| 449 | |
| 450 | /* Require newinstance for all user namespace mounts to ensure |
| 451 | * the mount options are not changed. |
| 452 | */ |
| 453 | if ((current_user_ns() != &init_user_ns) && !opts.newinstance) |
| 454 | return ERR_PTR(-EINVAL); |
| 455 | |
| 456 | if (opts.newinstance) |
| 457 | s = sget(fs_type, NULL, set_anon_super, flags, NULL); |
| 458 | else |
| 459 | s = sget(fs_type, compare_init_pts_sb, set_anon_super, flags, |
| 460 | NULL); |
| 461 | |
| 462 | if (IS_ERR(s)) |
| 463 | return ERR_CAST(s); |
| 464 | |
| 465 | if (!s->s_root) { |
| 466 | error = devpts_fill_super(s, data, flags & MS_SILENT ? 1 : 0); |
| 467 | if (error) |
| 468 | goto out_undo_sget; |
| 469 | s->s_flags |= MS_ACTIVE; |
| 470 | } |
| 471 | |
| 472 | memcpy(&(DEVPTS_SB(s))->mount_opts, &opts, sizeof(opts)); |
| 473 | |
| 474 | error = mknod_ptmx(s); |
| 475 | if (error) |
| 476 | goto out_undo_sget; |
| 477 | |
| 478 | return dget(s->s_root); |
| 479 | |
| 480 | out_undo_sget: |
| 481 | deactivate_locked_super(s); |
| 482 | return ERR_PTR(error); |
| 483 | } |
| 484 | |
| 485 | #else |
| 486 | /* |
| 487 | * This supports only the legacy single-instance semantics (no |
| 488 | * multiple-instance semantics) |
| 489 | */ |
| 490 | static struct dentry *devpts_mount(struct file_system_type *fs_type, int flags, |
| 491 | const char *dev_name, void *data) |
| 492 | { |
| 493 | return mount_single(fs_type, flags, data, devpts_fill_super); |
| 494 | } |
| 495 | #endif |
| 496 | |
| 497 | static void devpts_kill_sb(struct super_block *sb) |
| 498 | { |
| 499 | struct pts_fs_info *fsi = DEVPTS_SB(sb); |
| 500 | |
| 501 | ida_destroy(&fsi->allocated_ptys); |
| 502 | kfree(fsi); |
| 503 | kill_litter_super(sb); |
| 504 | } |
| 505 | |
| 506 | static struct file_system_type devpts_fs_type = { |
| 507 | .name = "devpts", |
| 508 | .mount = devpts_mount, |
| 509 | .kill_sb = devpts_kill_sb, |
| 510 | #ifdef CONFIG_DEVPTS_MULTIPLE_INSTANCES |
| 511 | .fs_flags = FS_USERNS_MOUNT | FS_USERNS_DEV_MOUNT, |
| 512 | #endif |
| 513 | }; |
| 514 | |
| 515 | /* |
| 516 | * The normal naming convention is simply /dev/pts/<number>; this conforms |
| 517 | * to the System V naming convention |
| 518 | */ |
| 519 | |
| 520 | int devpts_new_index(struct inode *ptmx_inode) |
| 521 | { |
| 522 | struct super_block *sb = pts_sb_from_inode(ptmx_inode); |
| 523 | struct pts_fs_info *fsi = DEVPTS_SB(sb); |
| 524 | int index; |
| 525 | int ida_ret; |
| 526 | |
| 527 | retry: |
| 528 | if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL)) |
| 529 | return -ENOMEM; |
| 530 | |
| 531 | mutex_lock(&allocated_ptys_lock); |
| 532 | if (pty_count >= pty_limit - |
| 533 | (fsi->mount_opts.newinstance ? pty_reserve : 0)) { |
| 534 | mutex_unlock(&allocated_ptys_lock); |
| 535 | return -ENOSPC; |
| 536 | } |
| 537 | |
| 538 | ida_ret = ida_get_new(&fsi->allocated_ptys, &index); |
| 539 | if (ida_ret < 0) { |
| 540 | mutex_unlock(&allocated_ptys_lock); |
| 541 | if (ida_ret == -EAGAIN) |
| 542 | goto retry; |
| 543 | return -EIO; |
| 544 | } |
| 545 | |
| 546 | if (index >= fsi->mount_opts.max) { |
| 547 | ida_remove(&fsi->allocated_ptys, index); |
| 548 | mutex_unlock(&allocated_ptys_lock); |
| 549 | return -ENOSPC; |
| 550 | } |
| 551 | pty_count++; |
| 552 | mutex_unlock(&allocated_ptys_lock); |
| 553 | return index; |
| 554 | } |
| 555 | |
| 556 | void devpts_kill_index(struct inode *ptmx_inode, int idx) |
| 557 | { |
| 558 | struct super_block *sb = pts_sb_from_inode(ptmx_inode); |
| 559 | struct pts_fs_info *fsi = DEVPTS_SB(sb); |
| 560 | |
| 561 | mutex_lock(&allocated_ptys_lock); |
| 562 | ida_remove(&fsi->allocated_ptys, idx); |
| 563 | pty_count--; |
| 564 | mutex_unlock(&allocated_ptys_lock); |
| 565 | } |
| 566 | |
| 567 | /** |
| 568 | * devpts_pty_new -- create a new inode in /dev/pts/ |
| 569 | * @ptmx_inode: inode of the master |
| 570 | * @device: major+minor of the node to be created |
| 571 | * @index: used as a name of the node |
| 572 | * @priv: what's given back by devpts_get_priv |
| 573 | * |
| 574 | * The created inode is returned. Remove it from /dev/pts/ by devpts_pty_kill. |
| 575 | */ |
| 576 | struct inode *devpts_pty_new(struct inode *ptmx_inode, dev_t device, int index, |
| 577 | void *priv) |
| 578 | { |
| 579 | struct dentry *dentry; |
| 580 | struct super_block *sb = pts_sb_from_inode(ptmx_inode); |
| 581 | struct inode *inode; |
| 582 | struct dentry *root = sb->s_root; |
| 583 | struct pts_fs_info *fsi = DEVPTS_SB(sb); |
| 584 | struct pts_mount_opts *opts = &fsi->mount_opts; |
| 585 | char s[12]; |
| 586 | |
| 587 | inode = new_inode(sb); |
| 588 | if (!inode) |
| 589 | return ERR_PTR(-ENOMEM); |
| 590 | |
| 591 | inode->i_ino = index + 3; |
| 592 | inode->i_uid = opts->setuid ? opts->uid : current_fsuid(); |
| 593 | inode->i_gid = opts->setgid ? opts->gid : current_fsgid(); |
| 594 | inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME; |
| 595 | init_special_inode(inode, S_IFCHR|opts->mode, device); |
| 596 | inode->i_private = priv; |
| 597 | |
| 598 | sprintf(s, "%d", index); |
| 599 | |
| 600 | mutex_lock(&root->d_inode->i_mutex); |
| 601 | |
| 602 | dentry = d_alloc_name(root, s); |
| 603 | if (dentry) { |
| 604 | d_add(dentry, inode); |
| 605 | fsnotify_create(root->d_inode, dentry); |
| 606 | } else { |
| 607 | iput(inode); |
| 608 | inode = ERR_PTR(-ENOMEM); |
| 609 | } |
| 610 | |
| 611 | mutex_unlock(&root->d_inode->i_mutex); |
| 612 | |
| 613 | return inode; |
| 614 | } |
| 615 | |
| 616 | /** |
| 617 | * devpts_get_priv -- get private data for a slave |
| 618 | * @pts_inode: inode of the slave |
| 619 | * |
| 620 | * Returns whatever was passed as priv in devpts_pty_new for a given inode. |
| 621 | */ |
| 622 | void *devpts_get_priv(struct inode *pts_inode) |
| 623 | { |
| 624 | struct dentry *dentry; |
| 625 | void *priv = NULL; |
| 626 | |
| 627 | BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR)); |
| 628 | |
| 629 | /* Ensure dentry has not been deleted by devpts_pty_kill() */ |
| 630 | dentry = d_find_alias(pts_inode); |
| 631 | if (!dentry) |
| 632 | return NULL; |
| 633 | |
| 634 | if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC) |
| 635 | priv = pts_inode->i_private; |
| 636 | |
| 637 | dput(dentry); |
| 638 | |
| 639 | return priv; |
| 640 | } |
| 641 | |
| 642 | /** |
| 643 | * devpts_pty_kill -- remove inode form /dev/pts/ |
| 644 | * @inode: inode of the slave to be removed |
| 645 | * |
| 646 | * This is an inverse operation of devpts_pty_new. |
| 647 | */ |
| 648 | void devpts_pty_kill(struct inode *inode) |
| 649 | { |
| 650 | struct super_block *sb = pts_sb_from_inode(inode); |
| 651 | struct dentry *root = sb->s_root; |
| 652 | struct dentry *dentry; |
| 653 | |
| 654 | BUG_ON(inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR)); |
| 655 | |
| 656 | mutex_lock(&root->d_inode->i_mutex); |
| 657 | |
| 658 | dentry = d_find_alias(inode); |
| 659 | |
| 660 | drop_nlink(inode); |
| 661 | d_delete(dentry); |
| 662 | dput(dentry); /* d_alloc_name() in devpts_pty_new() */ |
| 663 | dput(dentry); /* d_find_alias above */ |
| 664 | |
| 665 | mutex_unlock(&root->d_inode->i_mutex); |
| 666 | } |
| 667 | |
| 668 | static int __init init_devpts_fs(void) |
| 669 | { |
| 670 | int err = register_filesystem(&devpts_fs_type); |
| 671 | struct ctl_table_header *table; |
| 672 | |
| 673 | if (!err) { |
| 674 | table = register_sysctl_table(pty_root_table); |
| 675 | devpts_mnt = kern_mount(&devpts_fs_type); |
| 676 | if (IS_ERR(devpts_mnt)) { |
| 677 | err = PTR_ERR(devpts_mnt); |
| 678 | unregister_filesystem(&devpts_fs_type); |
| 679 | unregister_sysctl_table(table); |
| 680 | } |
| 681 | } |
| 682 | return err; |
| 683 | } |
| 684 | module_init(init_devpts_fs) |