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
  24 #include <asm/uaccess.h>
  25
  26 /*
  27  * Check permissions for extended attribute access.  This is a bit complicated
  28  * because different namespaces have very different rules.
  29  */
  30 static int
  31 xattr_permission(struct inode *inode, const char *name, int mask)
  32 {
  33         /*
  34          * We can never set or remove an extended attribute on a read-only
  35          * filesystem  or on an immutable / append-only inode.
  36          */
  37         if (mask & MAY_WRITE) {
  38                 if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
  39                         return -EPERM;
  40         }
  41
  42         /*
  43          * No restriction for security.* and system.* from the VFS.  Decision
  44          * on these is left to the underlying filesystem / security module.
  45          */
  46         if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||
  47             !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
  48                 return 0;
  49
  50         /*
  51          * The trusted.* namespace can only be accessed by privileged users.
  52          */
  53         if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
  54                 if (!capable(CAP_SYS_ADMIN))
  55                         return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
  56                 return 0;
  57         }
  58
  59         /*
  60          * In the user.* namespace, only regular files and directories can have
  61          * extended attributes. For sticky directories, only the owner and
  62          * privileged users can write attributes.
  63          */
  64         if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
  65                 if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
  66                         return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
  67                 if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&
  68                     (mask & MAY_WRITE) && !inode_owner_or_capable(inode))
  69                         return -EPERM;
  70         }
  71
  72         return inode_permission(inode, mask);
  73 }
  74
  75 /**
  76  *  __vfs_setxattr_noperm - perform setxattr operation without performing
  77  *  permission checks.
  78  *
  79  *  @dentry - object to perform setxattr on
  80  *  @name - xattr name to set
  81  *  @value - value to set @name to
  82  *  @size - size of @value
  83  *  @flags - flags to pass into filesystem operations
  84  *
  85  *  returns the result of the internal setxattr or setsecurity operations.
  86  *
  87  *  This function requires the caller to lock the inode's i_mutex before it
  88  *  is executed. It also assumes that the caller will make the appropriate
  89  *  permission checks.
  90  */
  91 int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
  92                 const void *value, size_t size, int flags)
  93 {
  94         struct inode *inode = dentry->d_inode;
  95         int error = -EOPNOTSUPP;
  96         int issec = !strncmp(name, XATTR_SECURITY_PREFIX,
  97                                    XATTR_SECURITY_PREFIX_LEN);
  98
  99         if (issec)
 100                 inode->i_flags &= ~S_NOSEC;
 101         if (inode->i_op->setxattr) {
 102                 error = inode->i_op->setxattr(dentry, name, value, size, flags);
 103                 if (!error) {
 104                         fsnotify_xattr(dentry);
 105                         security_inode_post_setxattr(dentry, name, value,
 106                                                      size, flags);
 107                 }
 108         } else if (issec) {
 109                 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
 110                 error = security_inode_setsecurity(inode, suffix, value,
 111                                                    size, flags);
 112                 if (!error)
 113                         fsnotify_xattr(dentry);
 114         }
 115
 116         return error;
 117 }
 118
 119
 120 int
 121 vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
 122                 size_t size, int flags)
 123 {
 124         struct inode *inode = dentry->d_inode;
 125         int error;
 126
 127         error = xattr_permission(inode, name, MAY_WRITE);
 128         if (error)
 129                 return error;
 130
 131         mutex_lock(&inode->i_mutex);
 132         error = security_inode_setxattr(dentry, name, value, size, flags);
 133         if (error)
 134                 goto out;
 135
 136         error = __vfs_setxattr_noperm(dentry, name, value, size, flags);
 137
 138 out:
 139         mutex_unlock(&inode->i_mutex);
 140         return error;
 141 }
 142 EXPORT_SYMBOL_GPL(vfs_setxattr);
 143
 144 ssize_t
 145 xattr_getsecurity(struct inode *inode, const char *name, void *value,
 146                         size_t size)
 147 {
 148         void *buffer = NULL;
 149         ssize_t len;
 150
 151         if (!value || !size) {
 152                 len = security_inode_getsecurity(inode, name, &buffer, false);
 153                 goto out_noalloc;
 154         }
 155
 156         len = security_inode_getsecurity(inode, name, &buffer, true);
 157         if (len < 0)
 158                 return len;
 159         if (size < len) {
 160                 len = -ERANGE;
 161                 goto out;
 162         }
 163         memcpy(value, buffer, len);
 164 out:
 165         security_release_secctx(buffer, len);
 166 out_noalloc:
 167         return len;
 168 }
 169 EXPORT_SYMBOL_GPL(xattr_getsecurity);
 170
 171 /*
 172  * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
 173  *
 174  * Allocate memory, if not already allocated, or re-allocate correct size,
 175  * before retrieving the extended attribute.
 176  *
 177  * Returns the result of alloc, if failed, or the getxattr operation.
 178  */
 179 ssize_t
 180 vfs_getxattr_alloc(struct dentry *dentry, const char *name, char **xattr_value,
 181                    size_t xattr_size, gfp_t flags)
 182 {
 183         struct inode *inode = dentry->d_inode;
 184         char *value = *xattr_value;
 185         int error;
 186
 187         error = xattr_permission(inode, name, MAY_READ);
 188         if (error)
 189                 return error;
 190
 191         if (!inode->i_op->getxattr)
 192                 return -EOPNOTSUPP;
 193
 194         error = inode->i_op->getxattr(dentry, name, NULL, 0);
 195         if (error < 0)
 196                 return error;
 197
 198         if (!value || (error > xattr_size)) {
 199                 value = krealloc(*xattr_value, error + 1, flags);
 200                 if (!value)
 201                         return -ENOMEM;
 202                 memset(value, 0, error + 1);
 203         }
 204
 205         error = inode->i_op->getxattr(dentry, name, value, error);
 206         *xattr_value = value;
 207         return error;
 208 }
 209
 210 /* Compare an extended attribute value with the given value */
 211 int vfs_xattr_cmp(struct dentry *dentry, const char *xattr_name,
 212                   const char *value, size_t size, gfp_t flags)
 213 {
 214         char *xattr_value = NULL;
 215         int rc;
 216
 217         rc = vfs_getxattr_alloc(dentry, xattr_name, &xattr_value, 0, flags);
 218         if (rc < 0)
 219                 return rc;
 220
 221         if ((rc != size) || (memcmp(xattr_value, value, rc) != 0))
 222                 rc = -EINVAL;
 223         else
 224                 rc = 0;
 225         kfree(xattr_value);
 226         return rc;
 227 }
 228
 229 ssize_t
 230 vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
 231 {
 232         struct inode *inode = dentry->d_inode;
 233         int error;
 234
 235         error = xattr_permission(inode, name, MAY_READ);
 236         if (error)
 237                 return error;
 238
 239         error = security_inode_getxattr(dentry, name);
 240         if (error)
 241                 return error;
 242
 243         if (!strncmp(name, XATTR_SECURITY_PREFIX,
 244                                 XATTR_SECURITY_PREFIX_LEN)) {
 245                 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
 246                 int ret = xattr_getsecurity(inode, suffix, value, size);
 247                 /*
 248                  * Only overwrite the return value if a security module
 249                  * is actually active.
 250                  */
 251                 if (ret == -EOPNOTSUPP)
 252                         goto nolsm;
 253                 return ret;
 254         }
 255 nolsm:
 256         if (inode->i_op->getxattr)
 257                 error = inode->i_op->getxattr(dentry, name, value, size);
 258         else
 259                 error = -EOPNOTSUPP;
 260
 261         return error;
 262 }
 263 EXPORT_SYMBOL_GPL(vfs_getxattr);
 264
 265 ssize_t
 266 vfs_listxattr(struct dentry *d, char *list, size_t size)
 267 {
 268         ssize_t error;
 269
 270         error = security_inode_listxattr(d);
 271         if (error)
 272                 return error;
 273         error = -EOPNOTSUPP;
 274         if (d->d_inode->i_op->listxattr) {
 275                 error = d->d_inode->i_op->listxattr(d, list, size);
 276         } else {
 277                 error = security_inode_listsecurity(d->d_inode, list, size);
 278                 if (size && error > size)
 279                         error = -ERANGE;
 280         }
 281         return error;
 282 }
 283 EXPORT_SYMBOL_GPL(vfs_listxattr);
 284
 285 int
 286 vfs_removexattr(struct dentry *dentry, const char *name)
 287 {
 288         struct inode *inode = dentry->d_inode;
 289         int error;
 290
 291         if (!inode->i_op->removexattr)
 292                 return -EOPNOTSUPP;
 293
 294         error = xattr_permission(inode, name, MAY_WRITE);
 295         if (error)
 296                 return error;
 297
 298         error = security_inode_removexattr(dentry, name);
 299         if (error)
 300                 return error;
 301
 302         mutex_lock(&inode->i_mutex);
 303         error = inode->i_op->removexattr(dentry, name);
 304         mutex_unlock(&inode->i_mutex);
 305
 306         if (!error) {
 307                 fsnotify_xattr(dentry);
 308                 evm_inode_post_removexattr(dentry, name);
 309         }
 310         return error;
 311 }
 312 EXPORT_SYMBOL_GPL(vfs_removexattr);
 313
 314
 315 /*
 316  * Extended attribute SET operations
 317  */
 318 static long
 319 setxattr(struct dentry *d, const char __user *name, const void __user *value,
 320          size_t size, int flags)
 321 {
 322         int error;
 323         void *kvalue = NULL;
 324         char kname[XATTR_NAME_MAX + 1];
 325
 326         if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
 327                 return -EINVAL;
 328
 329         error = strncpy_from_user(kname, name, sizeof(kname));
 330         if (error == 0 || error == sizeof(kname))
 331                 error = -ERANGE;
 332         if (error < 0)
 333                 return error;
 334
 335         if (size) {
 336                 if (size > XATTR_SIZE_MAX)
 337                         return -E2BIG;
 338                 kvalue = memdup_user(value, size);
 339                 if (IS_ERR(kvalue))
 340                         return PTR_ERR(kvalue);
 341         }
 342
 343         error = vfs_setxattr(d, kname, kvalue, size, flags);
 344         kfree(kvalue);
 345         return error;
 346 }
 347
 348 SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
 349                 const char __user *, name, const void __user *, value,
 350                 size_t, size, int, flags)
 351 {
 352         struct path path;
 353         int error;
 354
 355         error = user_path(pathname, &path);
 356         if (error)
 357                 return error;
 358         error = mnt_want_write(path.mnt);
 359         if (!error) {
 360                 error = setxattr(path.dentry, name, value, size, flags);
 361                 mnt_drop_write(path.mnt);
 362         }
 363         path_put(&path);
 364         return error;
 365 }
 366
 367 SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
 368                 const char __user *, name, const void __user *, value,
 369                 size_t, size, int, flags)
 370 {
 371         struct path path;
 372         int error;
 373
 374         error = user_lpath(pathname, &path);
 375         if (error)
 376                 return error;
 377         error = mnt_want_write(path.mnt);
 378         if (!error) {
 379                 error = setxattr(path.dentry, name, value, size, flags);
 380                 mnt_drop_write(path.mnt);
 381         }
 382         path_put(&path);
 383         return error;
 384 }
 385
 386 SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
 387                 const void __user *,value, size_t, size, int, flags)
 388 {
 389         struct file *f;
 390         struct dentry *dentry;
 391         int error = -EBADF;
 392
 393         f = fget(fd);
 394         if (!f)
 395                 return error;
 396         dentry = f->f_path.dentry;
 397         audit_inode(NULL, dentry);
 398         error = mnt_want_write_file(f);
 399         if (!error) {
 400                 error = setxattr(dentry, name, value, size, flags);
 401                 mnt_drop_write_file(f);
 402         }
 403         fput(f);
 404         return error;
 405 }
 406
 407 /*
 408  * Extended attribute GET operations
 409  */
 410 static ssize_t
 411 getxattr(struct dentry *d, const char __user *name, void __user *value,
 412          size_t size)
 413 {
 414         ssize_t error;
 415         void *kvalue = NULL;
 416         char kname[XATTR_NAME_MAX + 1];
 417
 418         error = strncpy_from_user(kname, name, sizeof(kname));
 419         if (error == 0 || error == sizeof(kname))
 420                 error = -ERANGE;
 421         if (error < 0)
 422                 return error;
 423
 424         if (size) {
 425                 if (size > XATTR_SIZE_MAX)
 426                         size = XATTR_SIZE_MAX;
 427                 kvalue = kzalloc(size, GFP_KERNEL);
 428                 if (!kvalue)
 429                         return -ENOMEM;
 430         }
 431
 432         error = vfs_getxattr(d, kname, kvalue, size);
 433         if (error > 0) {
 434                 if (size && copy_to_user(value, kvalue, error))
 435                         error = -EFAULT;
 436         } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
 437                 /* The file system tried to returned a value bigger
 438                    than XATTR_SIZE_MAX bytes. Not possible. */
 439                 error = -E2BIG;
 440         }
 441         kfree(kvalue);
 442         return error;
 443 }
 444
 445 SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
 446                 const char __user *, name, void __user *, value, size_t, size)
 447 {
 448         struct path path;
 449         ssize_t error;
 450
 451         error = user_path(pathname, &path);
 452         if (error)
 453                 return error;
 454         error = getxattr(path.dentry, name, value, size);
 455         path_put(&path);
 456         return error;
 457 }
 458
 459 SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
 460                 const char __user *, name, void __user *, value, size_t, size)
 461 {
 462         struct path path;
 463         ssize_t error;
 464
 465         error = user_lpath(pathname, &path);
 466         if (error)
 467                 return error;
 468         error = getxattr(path.dentry, name, value, size);
 469         path_put(&path);
 470         return error;
 471 }
 472
 473 SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
 474                 void __user *, value, size_t, size)
 475 {
 476         struct file *f;
 477         ssize_t error = -EBADF;
 478
 479         f = fget(fd);
 480         if (!f)
 481                 return error;
 482         audit_inode(NULL, f->f_path.dentry);
 483         error = getxattr(f->f_path.dentry, name, value, size);
 484         fput(f);
 485         return error;
 486 }
 487
 488 /*
 489  * Extended attribute LIST operations
 490  */
 491 static ssize_t
 492 listxattr(struct dentry *d, char __user *list, size_t size)
 493 {
 494         ssize_t error;
 495         char *klist = NULL;
 496         char *vlist = NULL;     /* If non-NULL, we used vmalloc() */
 497
 498         if (size) {
 499                 if (size > XATTR_LIST_MAX)
 500                         size = XATTR_LIST_MAX;
 501                 klist = kmalloc(size, __GFP_NOWARN | GFP_KERNEL);
 502                 if (!klist) {
 503                         vlist = vmalloc(size);
 504                         if (!vlist)
 505                                 return -ENOMEM;
 506                         klist = vlist;
 507                 }
 508         }
 509
 510         error = vfs_listxattr(d, klist, size);
 511         if (error > 0) {
 512                 if (size && copy_to_user(list, klist, error))
 513                         error = -EFAULT;
 514         } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
 515                 /* The file system tried to returned a list bigger
 516                    than XATTR_LIST_MAX bytes. Not possible. */
 517                 error = -E2BIG;
 518         }
 519         if (vlist)
 520                 vfree(vlist);
 521         else
 522                 kfree(klist);
 523         return error;
 524 }
 525
 526 SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
 527                 size_t, size)
 528 {
 529         struct path path;
 530         ssize_t error;
 531
 532         error = user_path(pathname, &path);
 533         if (error)
 534                 return error;
 535         error = listxattr(path.dentry, list, size);
 536         path_put(&path);
 537         return error;
 538 }
 539
 540 SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
 541                 size_t, size)
 542 {
 543         struct path path;
 544         ssize_t error;
 545
 546         error = user_lpath(pathname, &path);
 547         if (error)
 548                 return error;
 549         error = listxattr(path.dentry, list, size);
 550         path_put(&path);
 551         return error;
 552 }
 553
 554 SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
 555 {
 556         struct file *f;
 557         ssize_t error = -EBADF;
 558
 559         f = fget(fd);
 560         if (!f)
 561                 return error;
 562         audit_inode(NULL, f->f_path.dentry);
 563         error = listxattr(f->f_path.dentry, list, size);
 564         fput(f);
 565         return error;
 566 }
 567
 568 /*
 569  * Extended attribute REMOVE operations
 570  */
 571 static long
 572 removexattr(struct dentry *d, const char __user *name)
 573 {
 574         int error;
 575         char kname[XATTR_NAME_MAX + 1];
 576
 577         error = strncpy_from_user(kname, name, sizeof(kname));
 578         if (error == 0 || error == sizeof(kname))
 579                 error = -ERANGE;
 580         if (error < 0)
 581                 return error;
 582
 583         return vfs_removexattr(d, kname);
 584 }
 585
 586 SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
 587                 const char __user *, name)
 588 {
 589         struct path path;
 590         int error;
 591
 592         error = user_path(pathname, &path);
 593         if (error)
 594                 return error;
 595         error = mnt_want_write(path.mnt);
 596         if (!error) {
 597                 error = removexattr(path.dentry, name);
 598                 mnt_drop_write(path.mnt);
 599         }
 600         path_put(&path);
 601         return error;
 602 }
 603
 604 SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
 605                 const char __user *, name)
 606 {
 607         struct path path;
 608         int error;
 609
 610         error = user_lpath(pathname, &path);
 611         if (error)
 612                 return error;
 613         error = mnt_want_write(path.mnt);
 614         if (!error) {
 615                 error = removexattr(path.dentry, name);
 616                 mnt_drop_write(path.mnt);
 617         }
 618         path_put(&path);
 619         return error;
 620 }
 621
 622 SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
 623 {
 624         struct file *f;
 625         struct dentry *dentry;
 626         int error = -EBADF;
 627
 628         f = fget(fd);
 629         if (!f)
 630                 return error;
 631         dentry = f->f_path.dentry;
 632         audit_inode(NULL, dentry);
 633         error = mnt_want_write_file(f);
 634         if (!error) {
 635                 error = removexattr(dentry, name);
 636                 mnt_drop_write_file(f);
 637         }
 638         fput(f);
 639         return error;
 640 }
 641
 642
 643 static const char *
 644 strcmp_prefix(const char *a, const char *a_prefix)
 645 {
 646         while (*a_prefix && *a == *a_prefix) {
 647                 a++;
 648                 a_prefix++;
 649         }
 650         return *a_prefix ? NULL : a;
 651 }
 652
 653 /*
 654  * In order to implement different sets of xattr operations for each xattr
 655  * prefix with the generic xattr API, a filesystem should create a
 656  * null-terminated array of struct xattr_handler (one for each prefix) and
 657  * hang a pointer to it off of the s_xattr field of the superblock.
 658  *
 659  * The generic_fooxattr() functions will use this list to dispatch xattr
 660  * operations to the correct xattr_handler.
 661  */
 662 #define for_each_xattr_handler(handlers, handler)               \
 663                 for ((handler) = *(handlers)++;                 \
 664                         (handler) != NULL;                      \
 665                         (handler) = *(handlers)++)
 666
 667 /*
 668  * Find the xattr_handler with the matching prefix.
 669  */
 670 static const struct xattr_handler *
 671 xattr_resolve_name(const struct xattr_handler **handlers, const char **name)
 672 {
 673         const struct xattr_handler *handler;
 674
 675         if (!*name)
 676                 return NULL;
 677
 678         for_each_xattr_handler(handlers, handler) {
 679                 const char *n = strcmp_prefix(*name, handler->prefix);
 680                 if (n) {
 681                         *name = n;
 682                         break;
 683                 }
 684         }
 685         return handler;
 686 }
 687
 688 /*
 689  * Find the handler for the prefix and dispatch its get() operation.
 690  */
 691 ssize_t
 692 generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size)
 693 {
 694         const struct xattr_handler *handler;
 695
 696         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 697         if (!handler)
 698                 return -EOPNOTSUPP;
 699         return handler->get(dentry, name, buffer, size, handler->flags);
 700 }
 701
 702 /*
 703  * Combine the results of the list() operation from every xattr_handler in the
 704  * list.
 705  */
 706 ssize_t
 707 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 708 {
 709         const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
 710         unsigned int size = 0;
 711
 712         if (!buffer) {
 713                 for_each_xattr_handler(handlers, handler) {
 714                         size += handler->list(dentry, NULL, 0, NULL, 0,
 715                                               handler->flags);
 716                 }
 717         } else {
 718                 char *buf = buffer;
 719
 720                 for_each_xattr_handler(handlers, handler) {
 721                         size = handler->list(dentry, buf, buffer_size,
 722                                              NULL, 0, handler->flags);
 723                         if (size > buffer_size)
 724                                 return -ERANGE;
 725                         buf += size;
 726                         buffer_size -= size;
 727                 }
 728                 size = buf - buffer;
 729         }
 730         return size;
 731 }
 732
 733 /*
 734  * Find the handler for the prefix and dispatch its set() operation.
 735  */
 736 int
 737 generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags)
 738 {
 739         const struct xattr_handler *handler;
 740
 741         if (size == 0)
 742                 value = "";  /* empty EA, do not remove */
 743         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 744         if (!handler)
 745                 return -EOPNOTSUPP;
 746         return handler->set(dentry, name, value, size, flags, handler->flags);
 747 }
 748
 749 /*
 750  * Find the handler for the prefix and dispatch its set() operation to remove
 751  * any associated extended attribute.
 752  */
 753 int
 754 generic_removexattr(struct dentry *dentry, const char *name)
 755 {
 756         const struct xattr_handler *handler;
 757
 758         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 759         if (!handler)
 760                 return -EOPNOTSUPP;
 761         return handler->set(dentry, name, NULL, 0,
 762                             XATTR_REPLACE, handler->flags);
 763 }
 764
 765 EXPORT_SYMBOL(generic_getxattr);
 766 EXPORT_SYMBOL(generic_listxattr);
 767 EXPORT_SYMBOL(generic_setxattr);
 768 EXPORT_SYMBOL(generic_removexattr);