fs/xattr.c

   1 /*
   2   File: fs/xattr.c
   3
   4   Extended attribute handling.
   5
   6   Copyright (C) 2001 by Andreas Gruenbacher <a.gruenbacher@computer.org>
   7   Copyright (C) 2001 SGI - Silicon Graphics, Inc <linux-xfs@oss.sgi.com>
   8   Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
   9  */
  10 #include <linux/fs.h>
  11 #include <linux/slab.h>
  12 #include <linux/file.h>
  13 #include <linux/xattr.h>
  14 #include <linux/mount.h>
  15 #include <linux/namei.h>
  16 #include <linux/security.h>
  17 #include <linux/evm.h>
  18 #include <linux/syscalls.h>
  19 #include <linux/export.h>
  20 #include <linux/fsnotify.h>
  21 #include <linux/audit.h>
  22 #include <linux/vmalloc.h>
  23 #include <linux/posix_acl_xattr.h>
  24
  25 #include <asm/uaccess.h>
  26
  27 /*
  28  * Check permissions for extended attribute access.  This is a bit complicated
  29  * because different namespaces have very different rules.
  30  */
  31 static int
  32 xattr_permission(struct inode *inode, const char *name, int mask)
  33 {
  34         /*
  35          * We can never set or remove an extended attribute on a read-only
  36          * filesystem  or on an immutable / append-only inode.
  37          */
  38         if (mask & MAY_WRITE) {
  39                 if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
  40                         return -EPERM;
  41         }
  42
  43         /*
  44          * No restriction for security.* and system.* from the VFS.  Decision
  45          * on these is left to the underlying filesystem / security module.
  46          */
  47         if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||
  48             !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
  49                 return 0;
  50
  51         /*
  52          * The trusted.* namespace can only be accessed by privileged users.
  53          */
  54         if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
  55                 if (!capable(CAP_SYS_ADMIN))
  56                         return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
  57                 return 0;
  58         }
  59
  60         /*
  61          * In the user.* namespace, only regular files and directories can have
  62          * extended attributes. For sticky directories, only the owner and
  63          * privileged users can write attributes.
  64          */
  65         if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
  66                 if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
  67                         return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
  68                 if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&
  69                     (mask & MAY_WRITE) && !inode_owner_or_capable(inode))
  70                         return -EPERM;
  71         }
  72
  73         return inode_permission(inode, mask);
  74 }
  75
  76 /**
  77  *  __vfs_setxattr_noperm - perform setxattr operation without performing
  78  *  permission checks.
  79  *
  80  *  @dentry - object to perform setxattr on
  81  *  @name - xattr name to set
  82  *  @value - value to set @name to
  83  *  @size - size of @value
  84  *  @flags - flags to pass into filesystem operations
  85  *
  86  *  returns the result of the internal setxattr or setsecurity operations.
  87  *
  88  *  This function requires the caller to lock the inode's i_mutex before it
  89  *  is executed. It also assumes that the caller will make the appropriate
  90  *  permission checks.
  91  */
  92 int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
  93                 const void *value, size_t size, int flags)
  94 {
  95         struct inode *inode = dentry->d_inode;
  96         int error = -EOPNOTSUPP;
  97         int issec = !strncmp(name, XATTR_SECURITY_PREFIX,
  98                                    XATTR_SECURITY_PREFIX_LEN);
  99
 100         if (issec)
 101                 inode->i_flags &= ~S_NOSEC;
 102         if (inode->i_op->setxattr) {
 103                 error = inode->i_op->setxattr(dentry, name, value, size, flags);
 104                 if (!error) {
 105                         fsnotify_xattr(dentry);
 106                         security_inode_post_setxattr(dentry, name, value,
 107                                                      size, flags);
 108                 }
 109         } else if (issec) {
 110                 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
 111                 error = security_inode_setsecurity(inode, suffix, value,
 112                                                    size, flags);
 113                 if (!error)
 114                         fsnotify_xattr(dentry);
 115         }
 116
 117         return error;
 118 }
 119
 120
 121 int
 122 vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
 123                 size_t size, int flags)
 124 {
 125         struct inode *inode = dentry->d_inode;
 126         int error;
 127
 128         error = xattr_permission(inode, name, MAY_WRITE);
 129         if (error)
 130                 return error;
 131
 132         mutex_lock(&inode->i_mutex);
 133         error = security_inode_setxattr(dentry, name, value, size, flags);
 134         if (error)
 135                 goto out;
 136
 137         error = __vfs_setxattr_noperm(dentry, name, value, size, flags);
 138
 139 out:
 140         mutex_unlock(&inode->i_mutex);
 141         return error;
 142 }
 143 EXPORT_SYMBOL_GPL(vfs_setxattr);
 144
 145 ssize_t
 146 xattr_getsecurity(struct inode *inode, const char *name, void *value,
 147                         size_t size)
 148 {
 149         void *buffer = NULL;
 150         ssize_t len;
 151
 152         if (!value || !size) {
 153                 len = security_inode_getsecurity(inode, name, &buffer, false);
 154                 goto out_noalloc;
 155         }
 156
 157         len = security_inode_getsecurity(inode, name, &buffer, true);
 158         if (len < 0)
 159                 return len;
 160         if (size < len) {
 161                 len = -ERANGE;
 162                 goto out;
 163         }
 164         memcpy(value, buffer, len);
 165 out:
 166         security_release_secctx(buffer, len);
 167 out_noalloc:
 168         return len;
 169 }
 170 EXPORT_SYMBOL_GPL(xattr_getsecurity);
 171
 172 /*
 173  * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
 174  *
 175  * Allocate memory, if not already allocated, or re-allocate correct size,
 176  * before retrieving the extended attribute.
 177  *
 178  * Returns the result of alloc, if failed, or the getxattr operation.
 179  */
 180 ssize_t
 181 vfs_getxattr_alloc(struct dentry *dentry, const char *name, char **xattr_value,
 182                    size_t xattr_size, gfp_t flags)
 183 {
 184         struct inode *inode = dentry->d_inode;
 185         char *value = *xattr_value;
 186         int error;
 187
 188         error = xattr_permission(inode, name, MAY_READ);
 189         if (error)
 190                 return error;
 191
 192         if (!inode->i_op->getxattr)
 193                 return -EOPNOTSUPP;
 194
 195         error = inode->i_op->getxattr(dentry, name, NULL, 0);
 196         if (error < 0)
 197                 return error;
 198
 199         if (!value || (error > xattr_size)) {
 200                 value = krealloc(*xattr_value, error + 1, flags);
 201                 if (!value)
 202                         return -ENOMEM;
 203                 memset(value, 0, error + 1);
 204         }
 205
 206         error = inode->i_op->getxattr(dentry, name, value, error);
 207         *xattr_value = value;
 208         return error;
 209 }
 210
 211 /* Compare an extended attribute value with the given value */
 212 int vfs_xattr_cmp(struct dentry *dentry, const char *xattr_name,
 213                   const char *value, size_t size, gfp_t flags)
 214 {
 215         char *xattr_value = NULL;
 216         int rc;
 217
 218         rc = vfs_getxattr_alloc(dentry, xattr_name, &xattr_value, 0, flags);
 219         if (rc < 0)
 220                 return rc;
 221
 222         if ((rc != size) || (memcmp(xattr_value, value, rc) != 0))
 223                 rc = -EINVAL;
 224         else
 225                 rc = 0;
 226         kfree(xattr_value);
 227         return rc;
 228 }
 229
 230 ssize_t
 231 vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
 232 {
 233         struct inode *inode = dentry->d_inode;
 234         int error;
 235
 236         error = xattr_permission(inode, name, MAY_READ);
 237         if (error)
 238                 return error;
 239
 240         error = security_inode_getxattr(dentry, name);
 241         if (error)
 242                 return error;
 243
 244         if (!strncmp(name, XATTR_SECURITY_PREFIX,
 245                                 XATTR_SECURITY_PREFIX_LEN)) {
 246                 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
 247                 int ret = xattr_getsecurity(inode, suffix, value, size);
 248                 /*
 249                  * Only overwrite the return value if a security module
 250                  * is actually active.
 251                  */
 252                 if (ret == -EOPNOTSUPP)
 253                         goto nolsm;
 254                 return ret;
 255         }
 256 nolsm:
 257         if (inode->i_op->getxattr)
 258                 error = inode->i_op->getxattr(dentry, name, value, size);
 259         else
 260                 error = -EOPNOTSUPP;
 261
 262         return error;
 263 }
 264 EXPORT_SYMBOL_GPL(vfs_getxattr);
 265
 266 ssize_t
 267 vfs_listxattr(struct dentry *d, char *list, size_t size)
 268 {
 269         ssize_t error;
 270
 271         error = security_inode_listxattr(d);
 272         if (error)
 273                 return error;
 274         error = -EOPNOTSUPP;
 275         if (d->d_inode->i_op->listxattr) {
 276                 error = d->d_inode->i_op->listxattr(d, list, size);
 277         } else {
 278                 error = security_inode_listsecurity(d->d_inode, list, size);
 279                 if (size && error > size)
 280                         error = -ERANGE;
 281         }
 282         return error;
 283 }
 284 EXPORT_SYMBOL_GPL(vfs_listxattr);
 285
 286 int
 287 vfs_removexattr(struct dentry *dentry, const char *name)
 288 {
 289         struct inode *inode = dentry->d_inode;
 290         int error;
 291
 292         if (!inode->i_op->removexattr)
 293                 return -EOPNOTSUPP;
 294
 295         error = xattr_permission(inode, name, MAY_WRITE);
 296         if (error)
 297                 return error;
 298
 299         error = security_inode_removexattr(dentry, name);
 300         if (error)
 301                 return error;
 302
 303         mutex_lock(&inode->i_mutex);
 304         error = inode->i_op->removexattr(dentry, name);
 305         mutex_unlock(&inode->i_mutex);
 306
 307         if (!error) {
 308                 fsnotify_xattr(dentry);
 309                 evm_inode_post_removexattr(dentry, name);
 310         }
 311         return error;
 312 }
 313 EXPORT_SYMBOL_GPL(vfs_removexattr);
 314
 315
 316 /*
 317  * Extended attribute SET operations
 318  */
 319 static long
 320 setxattr(struct dentry *d, const char __user *name, const void __user *value,
 321          size_t size, int flags)
 322 {
 323         int error;
 324         void *kvalue = NULL;
 325         void *vvalue = NULL;    /* If non-NULL, we used vmalloc() */
 326         char kname[XATTR_NAME_MAX + 1];
 327
 328         if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
 329                 return -EINVAL;
 330
 331         error = strncpy_from_user(kname, name, sizeof(kname));
 332         if (error == 0 || error == sizeof(kname))
 333                 error = -ERANGE;
 334         if (error < 0)
 335                 return error;
 336
 337         if (size) {
 338                 if (size > XATTR_SIZE_MAX)
 339                         return -E2BIG;
 340                 kvalue = kmalloc(size, GFP_KERNEL | __GFP_NOWARN);
 341                 if (!kvalue) {
 342                         vvalue = vmalloc(size);
 343                         if (!vvalue)
 344                                 return -ENOMEM;
 345                         kvalue = vvalue;
 346                 }
 347                 if (copy_from_user(kvalue, value, size)) {
 348                         error = -EFAULT;
 349                         goto out;
 350                 }
 351                 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
 352                     (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
 353                         posix_acl_fix_xattr_from_user(kvalue, size);
 354         }
 355
 356         error = vfs_setxattr(d, kname, kvalue, size, flags);
 357 out:
 358         if (vvalue)
 359                 vfree(vvalue);
 360         else
 361                 kfree(kvalue);
 362         return error;
 363 }
 364
 365 SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
 366                 const char __user *, name, const void __user *, value,
 367                 size_t, size, int, flags)
 368 {
 369         struct path path;
 370         int error;
 371
 372         error = user_path(pathname, &path);
 373         if (error)
 374                 return error;
 375         error = mnt_want_write(path.mnt);
 376         if (!error) {
 377                 error = setxattr(path.dentry, name, value, size, flags);
 378                 mnt_drop_write(path.mnt);
 379         }
 380         path_put(&path);
 381         return error;
 382 }
 383
 384 SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
 385                 const char __user *, name, const void __user *, value,
 386                 size_t, size, int, flags)
 387 {
 388         struct path path;
 389         int error;
 390
 391         error = user_lpath(pathname, &path);
 392         if (error)
 393                 return error;
 394         error = mnt_want_write(path.mnt);
 395         if (!error) {
 396                 error = setxattr(path.dentry, name, value, size, flags);
 397                 mnt_drop_write(path.mnt);
 398         }
 399         path_put(&path);
 400         return error;
 401 }
 402
 403 SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
 404                 const void __user *,value, size_t, size, int, flags)
 405 {
 406         struct fd f = fdget(fd);
 407         struct dentry *dentry;
 408         int error = -EBADF;
 409
 410         if (!f.file)
 411                 return error;
 412         dentry = f.file->f_path.dentry;
 413         audit_inode(NULL, dentry);
 414         error = mnt_want_write_file(f.file);
 415         if (!error) {
 416                 error = setxattr(dentry, name, value, size, flags);
 417                 mnt_drop_write_file(f.file);
 418         }
 419         fdput(f);
 420         return error;
 421 }
 422
 423 /*
 424  * Extended attribute GET operations
 425  */
 426 static ssize_t
 427 getxattr(struct dentry *d, const char __user *name, void __user *value,
 428          size_t size)
 429 {
 430         ssize_t error;
 431         void *kvalue = NULL;
 432         void *vvalue = NULL;
 433         char kname[XATTR_NAME_MAX + 1];
 434
 435         error = strncpy_from_user(kname, name, sizeof(kname));
 436         if (error == 0 || error == sizeof(kname))
 437                 error = -ERANGE;
 438         if (error < 0)
 439                 return error;
 440
 441         if (size) {
 442                 if (size > XATTR_SIZE_MAX)
 443                         size = XATTR_SIZE_MAX;
 444                 kvalue = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
 445                 if (!kvalue) {
 446                         vvalue = vmalloc(size);
 447                         if (!vvalue)
 448                                 return -ENOMEM;
 449                         kvalue = vvalue;
 450                 }
 451         }
 452
 453         error = vfs_getxattr(d, kname, kvalue, size);
 454         if (error > 0) {
 455                 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
 456                     (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
 457                         posix_acl_fix_xattr_to_user(kvalue, size);
 458                 if (size && copy_to_user(value, kvalue, error))
 459                         error = -EFAULT;
 460         } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
 461                 /* The file system tried to returned a value bigger
 462                    than XATTR_SIZE_MAX bytes. Not possible. */
 463                 error = -E2BIG;
 464         }
 465         if (vvalue)
 466                 vfree(vvalue);
 467         else
 468                 kfree(kvalue);
 469         return error;
 470 }
 471
 472 SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
 473                 const char __user *, name, void __user *, value, size_t, size)
 474 {
 475         struct path path;
 476         ssize_t error;
 477
 478         error = user_path(pathname, &path);
 479         if (error)
 480                 return error;
 481         error = getxattr(path.dentry, name, value, size);
 482         path_put(&path);
 483         return error;
 484 }
 485
 486 SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
 487                 const char __user *, name, void __user *, value, size_t, size)
 488 {
 489         struct path path;
 490         ssize_t error;
 491
 492         error = user_lpath(pathname, &path);
 493         if (error)
 494                 return error;
 495         error = getxattr(path.dentry, name, value, size);
 496         path_put(&path);
 497         return error;
 498 }
 499
 500 SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
 501                 void __user *, value, size_t, size)
 502 {
 503         struct fd f = fdget(fd);
 504         ssize_t error = -EBADF;
 505
 506         if (!f.file)
 507                 return error;
 508         audit_inode(NULL, f.file->f_path.dentry);
 509         error = getxattr(f.file->f_path.dentry, name, value, size);
 510         fdput(f);
 511         return error;
 512 }
 513
 514 /*
 515  * Extended attribute LIST operations
 516  */
 517 static ssize_t
 518 listxattr(struct dentry *d, char __user *list, size_t size)
 519 {
 520         ssize_t error;
 521         char *klist = NULL;
 522         char *vlist = NULL;     /* If non-NULL, we used vmalloc() */
 523
 524         if (size) {
 525                 if (size > XATTR_LIST_MAX)
 526                         size = XATTR_LIST_MAX;
 527                 klist = kmalloc(size, __GFP_NOWARN | GFP_KERNEL);
 528                 if (!klist) {
 529                         vlist = vmalloc(size);
 530                         if (!vlist)
 531                                 return -ENOMEM;
 532                         klist = vlist;
 533                 }
 534         }
 535
 536         error = vfs_listxattr(d, klist, size);
 537         if (error > 0) {
 538                 if (size && copy_to_user(list, klist, error))
 539                         error = -EFAULT;
 540         } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
 541                 /* The file system tried to returned a list bigger
 542                    than XATTR_LIST_MAX bytes. Not possible. */
 543                 error = -E2BIG;
 544         }
 545         if (vlist)
 546                 vfree(vlist);
 547         else
 548                 kfree(klist);
 549         return error;
 550 }
 551
 552 SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
 553                 size_t, size)
 554 {
 555         struct path path;
 556         ssize_t error;
 557
 558         error = user_path(pathname, &path);
 559         if (error)
 560                 return error;
 561         error = listxattr(path.dentry, list, size);
 562         path_put(&path);
 563         return error;
 564 }
 565
 566 SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
 567                 size_t, size)
 568 {
 569         struct path path;
 570         ssize_t error;
 571
 572         error = user_lpath(pathname, &path);
 573         if (error)
 574                 return error;
 575         error = listxattr(path.dentry, list, size);
 576         path_put(&path);
 577         return error;
 578 }
 579
 580 SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
 581 {
 582         struct fd f = fdget(fd);
 583         ssize_t error = -EBADF;
 584
 585         if (!f.file)
 586                 return error;
 587         audit_inode(NULL, f.file->f_path.dentry);
 588         error = listxattr(f.file->f_path.dentry, list, size);
 589         fdput(f);
 590         return error;
 591 }
 592
 593 /*
 594  * Extended attribute REMOVE operations
 595  */
 596 static long
 597 removexattr(struct dentry *d, const char __user *name)
 598 {
 599         int error;
 600         char kname[XATTR_NAME_MAX + 1];
 601
 602         error = strncpy_from_user(kname, name, sizeof(kname));
 603         if (error == 0 || error == sizeof(kname))
 604                 error = -ERANGE;
 605         if (error < 0)
 606                 return error;
 607
 608         return vfs_removexattr(d, kname);
 609 }
 610
 611 SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
 612                 const char __user *, name)
 613 {
 614         struct path path;
 615         int error;
 616
 617         error = user_path(pathname, &path);
 618         if (error)
 619                 return error;
 620         error = mnt_want_write(path.mnt);
 621         if (!error) {
 622                 error = removexattr(path.dentry, name);
 623                 mnt_drop_write(path.mnt);
 624         }
 625         path_put(&path);
 626         return error;
 627 }
 628
 629 SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
 630                 const char __user *, name)
 631 {
 632         struct path path;
 633         int error;
 634
 635         error = user_lpath(pathname, &path);
 636         if (error)
 637                 return error;
 638         error = mnt_want_write(path.mnt);
 639         if (!error) {
 640                 error = removexattr(path.dentry, name);
 641                 mnt_drop_write(path.mnt);
 642         }
 643         path_put(&path);
 644         return error;
 645 }
 646
 647 SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
 648 {
 649         struct fd f = fdget(fd);
 650         struct dentry *dentry;
 651         int error = -EBADF;
 652
 653         if (!f.file)
 654                 return error;
 655         dentry = f.file->f_path.dentry;
 656         audit_inode(NULL, dentry);
 657         error = mnt_want_write_file(f.file);
 658         if (!error) {
 659                 error = removexattr(dentry, name);
 660                 mnt_drop_write_file(f.file);
 661         }
 662         fdput(f);
 663         return error;
 664 }
 665
 666
 667 static const char *
 668 strcmp_prefix(const char *a, const char *a_prefix)
 669 {
 670         while (*a_prefix && *a == *a_prefix) {
 671                 a++;
 672                 a_prefix++;
 673         }
 674         return *a_prefix ? NULL : a;
 675 }
 676
 677 /*
 678  * In order to implement different sets of xattr operations for each xattr
 679  * prefix with the generic xattr API, a filesystem should create a
 680  * null-terminated array of struct xattr_handler (one for each prefix) and
 681  * hang a pointer to it off of the s_xattr field of the superblock.
 682  *
 683  * The generic_fooxattr() functions will use this list to dispatch xattr
 684  * operations to the correct xattr_handler.
 685  */
 686 #define for_each_xattr_handler(handlers, handler)               \
 687                 for ((handler) = *(handlers)++;                 \
 688                         (handler) != NULL;                      \
 689                         (handler) = *(handlers)++)
 690
 691 /*
 692  * Find the xattr_handler with the matching prefix.
 693  */
 694 static const struct xattr_handler *
 695 xattr_resolve_name(const struct xattr_handler **handlers, const char **name)
 696 {
 697         const struct xattr_handler *handler;
 698
 699         if (!*name)
 700                 return NULL;
 701
 702         for_each_xattr_handler(handlers, handler) {
 703                 const char *n = strcmp_prefix(*name, handler->prefix);
 704                 if (n) {
 705                         *name = n;
 706                         break;
 707                 }
 708         }
 709         return handler;
 710 }
 711
 712 /*
 713  * Find the handler for the prefix and dispatch its get() operation.
 714  */
 715 ssize_t
 716 generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size)
 717 {
 718         const struct xattr_handler *handler;
 719
 720         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 721         if (!handler)
 722                 return -EOPNOTSUPP;
 723         return handler->get(dentry, name, buffer, size, handler->flags);
 724 }
 725
 726 /*
 727  * Combine the results of the list() operation from every xattr_handler in the
 728  * list.
 729  */
 730 ssize_t
 731 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 732 {
 733         const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
 734         unsigned int size = 0;
 735
 736         if (!buffer) {
 737                 for_each_xattr_handler(handlers, handler) {
 738                         size += handler->list(dentry, NULL, 0, NULL, 0,
 739                                               handler->flags);
 740                 }
 741         } else {
 742                 char *buf = buffer;
 743
 744                 for_each_xattr_handler(handlers, handler) {
 745                         size = handler->list(dentry, buf, buffer_size,
 746                                              NULL, 0, handler->flags);
 747                         if (size > buffer_size)
 748                                 return -ERANGE;
 749                         buf += size;
 750                         buffer_size -= size;
 751                 }
 752                 size = buf - buffer;
 753         }
 754         return size;
 755 }
 756
 757 /*
 758  * Find the handler for the prefix and dispatch its set() operation.
 759  */
 760 int
 761 generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags)
 762 {
 763         const struct xattr_handler *handler;
 764
 765         if (size == 0)
 766                 value = "";  /* empty EA, do not remove */
 767         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 768         if (!handler)
 769                 return -EOPNOTSUPP;
 770         return handler->set(dentry, name, value, size, flags, handler->flags);
 771 }
 772
 773 /*
 774  * Find the handler for the prefix and dispatch its set() operation to remove
 775  * any associated extended attribute.
 776  */
 777 int
 778 generic_removexattr(struct dentry *dentry, const char *name)
 779 {
 780         const struct xattr_handler *handler;
 781
 782         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 783         if (!handler)
 784                 return -EOPNOTSUPP;
 785         return handler->set(dentry, name, NULL, 0,
 786                             XATTR_REPLACE, handler->flags);
 787 }
 788
 789 EXPORT_SYMBOL(generic_getxattr);
 790 EXPORT_SYMBOL(generic_listxattr);
 791 EXPORT_SYMBOL(generic_setxattr);
 792 EXPORT_SYMBOL(generic_removexattr);
 793
 794 /*
 795  * Allocate new xattr and copy in the value; but leave the name to callers.
 796  */
 797 struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
 798 {
 799         struct simple_xattr *new_xattr;
 800         size_t len;
 801
 802         /* wrap around? */
 803         len = sizeof(*new_xattr) + size;
 804         if (len <= sizeof(*new_xattr))
 805                 return NULL;
 806
 807         new_xattr = kmalloc(len, GFP_KERNEL);
 808         if (!new_xattr)
 809                 return NULL;
 810
 811         new_xattr->size = size;
 812         memcpy(new_xattr->value, value, size);
 813         return new_xattr;
 814 }
 815
 816 /*
 817  * xattr GET operation for in-memory/pseudo filesystems
 818  */
 819 int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
 820                      void *buffer, size_t size)
 821 {
 822         struct simple_xattr *xattr;
 823         int ret = -ENODATA;
 824
 825         spin_lock(&xattrs->lock);
 826         list_for_each_entry(xattr, &xattrs->head, list) {
 827                 if (strcmp(name, xattr->name))
 828                         continue;
 829
 830                 ret = xattr->size;
 831                 if (buffer) {
 832                         if (size < xattr->size)
 833                                 ret = -ERANGE;
 834                         else
 835                                 memcpy(buffer, xattr->value, xattr->size);
 836                 }
 837                 break;
 838         }
 839         spin_unlock(&xattrs->lock);
 840         return ret;
 841 }
 842
 843 static int __simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
 844                               const void *value, size_t size, int flags)
 845 {
 846         struct simple_xattr *xattr;
 847         struct simple_xattr *uninitialized_var(new_xattr);
 848         int err = 0;
 849
 850         /* value == NULL means remove */
 851         if (value) {
 852                 new_xattr = simple_xattr_alloc(value, size);
 853                 if (!new_xattr)
 854                         return -ENOMEM;
 855
 856                 new_xattr->name = kstrdup(name, GFP_KERNEL);
 857                 if (!new_xattr->name) {
 858                         kfree(new_xattr);
 859                         return -ENOMEM;
 860                 }
 861         }
 862
 863         spin_lock(&xattrs->lock);
 864         list_for_each_entry(xattr, &xattrs->head, list) {
 865                 if (!strcmp(name, xattr->name)) {
 866                         if (flags & XATTR_CREATE) {
 867                                 xattr = new_xattr;
 868                                 err = -EEXIST;
 869                         } else if (new_xattr) {
 870                                 list_replace(&xattr->list, &new_xattr->list);
 871                         } else {
 872                                 list_del(&xattr->list);
 873                         }
 874                         goto out;
 875                 }
 876         }
 877         if (flags & XATTR_REPLACE) {
 878                 xattr = new_xattr;
 879                 err = -ENODATA;
 880         } else {
 881                 list_add(&new_xattr->list, &xattrs->head);
 882                 xattr = NULL;
 883         }
 884 out:
 885         spin_unlock(&xattrs->lock);
 886         if (xattr) {
 887                 kfree(xattr->name);
 888                 kfree(xattr);
 889         }
 890         return err;
 891
 892 }
 893
 894 /**
 895  * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
 896  * @xattrs: target simple_xattr list
 897  * @name: name of the new extended attribute
 898  * @value: value of the new xattr. If %NULL, will remove the attribute
 899  * @size: size of the new xattr
 900  * @flags: %XATTR_{CREATE|REPLACE}
 901  *
 902  * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
 903  * with -EEXIST.  If %XATTR_REPLACE is set, the xattr should exist;
 904  * otherwise, fails with -ENODATA.
 905  *
 906  * Returns 0 on success, -errno on failure.
 907  */
 908 int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
 909                      const void *value, size_t size, int flags)
 910 {
 911         if (size == 0)
 912                 value = ""; /* empty EA, do not remove */
 913         return __simple_xattr_set(xattrs, name, value, size, flags);
 914 }
 915
 916 /*
 917  * xattr REMOVE operation for in-memory/pseudo filesystems
 918  */
 919 int simple_xattr_remove(struct simple_xattrs *xattrs, const char *name)
 920 {
 921         return __simple_xattr_set(xattrs, name, NULL, 0, XATTR_REPLACE);
 922 }
 923
 924 static bool xattr_is_trusted(const char *name)
 925 {
 926         return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
 927 }
 928
 929 /*
 930  * xattr LIST operation for in-memory/pseudo filesystems
 931  */
 932 ssize_t simple_xattr_list(struct simple_xattrs *xattrs, char *buffer,
 933                           size_t size)
 934 {
 935         bool trusted = capable(CAP_SYS_ADMIN);
 936         struct simple_xattr *xattr;
 937         size_t used = 0;
 938
 939         spin_lock(&xattrs->lock);
 940         list_for_each_entry(xattr, &xattrs->head, list) {
 941                 size_t len;
 942
 943                 /* skip "trusted." attributes for unprivileged callers */
 944                 if (!trusted && xattr_is_trusted(xattr->name))
 945                         continue;
 946
 947                 len = strlen(xattr->name) + 1;
 948                 used += len;
 949                 if (buffer) {
 950                         if (size < used) {
 951                                 used = -ERANGE;
 952                                 break;
 953                         }
 954                         memcpy(buffer, xattr->name, len);
 955                         buffer += len;
 956                 }
 957         }
 958         spin_unlock(&xattrs->lock);
 959
 960         return used;
 961 }
 962
 963 /*
 964  * Adds an extended attribute to the list
 965  */
 966 void simple_xattr_list_add(struct simple_xattrs *xattrs,
 967                            struct simple_xattr *new_xattr)
 968 {
 969         spin_lock(&xattrs->lock);
 970         list_add(&new_xattr->list, &xattrs->head);
 971         spin_unlock(&xattrs->lock);
 972 }