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         void *vvalue = NULL;    /* If non-NULL, we used vmalloc() */
 325         char kname[XATTR_NAME_MAX + 1];
 326
 327         if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
 328                 return -EINVAL;
 329
 330         error = strncpy_from_user(kname, name, sizeof(kname));
 331         if (error == 0 || error == sizeof(kname))
 332                 error = -ERANGE;
 333         if (error < 0)
 334                 return error;
 335
 336         if (size) {
 337                 if (size > XATTR_SIZE_MAX)
 338                         return -E2BIG;
 339                 kvalue = kmalloc(size, GFP_KERNEL | __GFP_NOWARN);
 340                 if (!kvalue) {
 341                         vvalue = vmalloc(size);
 342                         if (!vvalue)
 343                                 return -ENOMEM;
 344                         kvalue = vvalue;
 345                 }
 346                 if (copy_from_user(kvalue, value, size)) {
 347                         error = -EFAULT;
 348                         goto out;
 349                 }
 350         }
 351
 352         error = vfs_setxattr(d, kname, kvalue, size, flags);
 353 out:
 354         if (vvalue)
 355                 vfree(vvalue);
 356         else
 357                 kfree(kvalue);
 358         return error;
 359 }
 360
 361 SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
 362                 const char __user *, name, const void __user *, value,
 363                 size_t, size, int, flags)
 364 {
 365         struct path path;
 366         int error;
 367
 368         error = user_path(pathname, &path);
 369         if (error)
 370                 return error;
 371         error = mnt_want_write(path.mnt);
 372         if (!error) {
 373                 error = setxattr(path.dentry, name, value, size, flags);
 374                 mnt_drop_write(path.mnt);
 375         }
 376         path_put(&path);
 377         return error;
 378 }
 379
 380 SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
 381                 const char __user *, name, const void __user *, value,
 382                 size_t, size, int, flags)
 383 {
 384         struct path path;
 385         int error;
 386
 387         error = user_lpath(pathname, &path);
 388         if (error)
 389                 return error;
 390         error = mnt_want_write(path.mnt);
 391         if (!error) {
 392                 error = setxattr(path.dentry, name, value, size, flags);
 393                 mnt_drop_write(path.mnt);
 394         }
 395         path_put(&path);
 396         return error;
 397 }
 398
 399 SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
 400                 const void __user *,value, size_t, size, int, flags)
 401 {
 402         int fput_needed;
 403         struct file *f;
 404         struct dentry *dentry;
 405         int error = -EBADF;
 406
 407         f = fget_light(fd, &fput_needed);
 408         if (!f)
 409                 return error;
 410         dentry = f->f_path.dentry;
 411         audit_inode(NULL, dentry);
 412         error = mnt_want_write_file(f);
 413         if (!error) {
 414                 error = setxattr(dentry, name, value, size, flags);
 415                 mnt_drop_write_file(f);
 416         }
 417         fput_light(f, fput_needed);
 418         return error;
 419 }
 420
 421 /*
 422  * Extended attribute GET operations
 423  */
 424 static ssize_t
 425 getxattr(struct dentry *d, const char __user *name, void __user *value,
 426          size_t size)
 427 {
 428         ssize_t error;
 429         void *kvalue = NULL;
 430         char kname[XATTR_NAME_MAX + 1];
 431
 432         error = strncpy_from_user(kname, name, sizeof(kname));
 433         if (error == 0 || error == sizeof(kname))
 434                 error = -ERANGE;
 435         if (error < 0)
 436                 return error;
 437
 438         if (size) {
 439                 if (size > XATTR_SIZE_MAX)
 440                         size = XATTR_SIZE_MAX;
 441                 kvalue = kzalloc(size, GFP_KERNEL);
 442                 if (!kvalue)
 443                         return -ENOMEM;
 444         }
 445
 446         error = vfs_getxattr(d, kname, kvalue, size);
 447         if (error > 0) {
 448                 if (size && copy_to_user(value, kvalue, error))
 449                         error = -EFAULT;
 450         } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
 451                 /* The file system tried to returned a value bigger
 452                    than XATTR_SIZE_MAX bytes. Not possible. */
 453                 error = -E2BIG;
 454         }
 455         kfree(kvalue);
 456         return error;
 457 }
 458
 459 SYSCALL_DEFINE4(getxattr, 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_path(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(lgetxattr, const char __user *, pathname,
 474                 const char __user *, name, void __user *, value, size_t, size)
 475 {
 476         struct path path;
 477         ssize_t error;
 478
 479         error = user_lpath(pathname, &path);
 480         if (error)
 481                 return error;
 482         error = getxattr(path.dentry, name, value, size);
 483         path_put(&path);
 484         return error;
 485 }
 486
 487 SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
 488                 void __user *, value, size_t, size)
 489 {
 490         int fput_needed;
 491         struct file *f;
 492         ssize_t error = -EBADF;
 493
 494         f = fget_light(fd, &fput_needed);
 495         if (!f)
 496                 return error;
 497         audit_inode(NULL, f->f_path.dentry);
 498         error = getxattr(f->f_path.dentry, name, value, size);
 499         fput_light(f, fput_needed);
 500         return error;
 501 }
 502
 503 /*
 504  * Extended attribute LIST operations
 505  */
 506 static ssize_t
 507 listxattr(struct dentry *d, char __user *list, size_t size)
 508 {
 509         ssize_t error;
 510         char *klist = NULL;
 511         char *vlist = NULL;     /* If non-NULL, we used vmalloc() */
 512
 513         if (size) {
 514                 if (size > XATTR_LIST_MAX)
 515                         size = XATTR_LIST_MAX;
 516                 klist = kmalloc(size, __GFP_NOWARN | GFP_KERNEL);
 517                 if (!klist) {
 518                         vlist = vmalloc(size);
 519                         if (!vlist)
 520                                 return -ENOMEM;
 521                         klist = vlist;
 522                 }
 523         }
 524
 525         error = vfs_listxattr(d, klist, size);
 526         if (error > 0) {
 527                 if (size && copy_to_user(list, klist, error))
 528                         error = -EFAULT;
 529         } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
 530                 /* The file system tried to returned a list bigger
 531                    than XATTR_LIST_MAX bytes. Not possible. */
 532                 error = -E2BIG;
 533         }
 534         if (vlist)
 535                 vfree(vlist);
 536         else
 537                 kfree(klist);
 538         return error;
 539 }
 540
 541 SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
 542                 size_t, size)
 543 {
 544         struct path path;
 545         ssize_t error;
 546
 547         error = user_path(pathname, &path);
 548         if (error)
 549                 return error;
 550         error = listxattr(path.dentry, list, size);
 551         path_put(&path);
 552         return error;
 553 }
 554
 555 SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
 556                 size_t, size)
 557 {
 558         struct path path;
 559         ssize_t error;
 560
 561         error = user_lpath(pathname, &path);
 562         if (error)
 563                 return error;
 564         error = listxattr(path.dentry, list, size);
 565         path_put(&path);
 566         return error;
 567 }
 568
 569 SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
 570 {
 571         int fput_needed;
 572         struct file *f;
 573         ssize_t error = -EBADF;
 574
 575         f = fget_light(fd, &fput_needed);
 576         if (!f)
 577                 return error;
 578         audit_inode(NULL, f->f_path.dentry);
 579         error = listxattr(f->f_path.dentry, list, size);
 580         fput_light(f, fput_needed);
 581         return error;
 582 }
 583
 584 /*
 585  * Extended attribute REMOVE operations
 586  */
 587 static long
 588 removexattr(struct dentry *d, const char __user *name)
 589 {
 590         int error;
 591         char kname[XATTR_NAME_MAX + 1];
 592
 593         error = strncpy_from_user(kname, name, sizeof(kname));
 594         if (error == 0 || error == sizeof(kname))
 595                 error = -ERANGE;
 596         if (error < 0)
 597                 return error;
 598
 599         return vfs_removexattr(d, kname);
 600 }
 601
 602 SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
 603                 const char __user *, name)
 604 {
 605         struct path path;
 606         int error;
 607
 608         error = user_path(pathname, &path);
 609         if (error)
 610                 return error;
 611         error = mnt_want_write(path.mnt);
 612         if (!error) {
 613                 error = removexattr(path.dentry, name);
 614                 mnt_drop_write(path.mnt);
 615         }
 616         path_put(&path);
 617         return error;
 618 }
 619
 620 SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
 621                 const char __user *, name)
 622 {
 623         struct path path;
 624         int error;
 625
 626         error = user_lpath(pathname, &path);
 627         if (error)
 628                 return error;
 629         error = mnt_want_write(path.mnt);
 630         if (!error) {
 631                 error = removexattr(path.dentry, name);
 632                 mnt_drop_write(path.mnt);
 633         }
 634         path_put(&path);
 635         return error;
 636 }
 637
 638 SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
 639 {
 640         int fput_needed;
 641         struct file *f;
 642         struct dentry *dentry;
 643         int error = -EBADF;
 644
 645         f = fget_light(fd, &fput_needed);
 646         if (!f)
 647                 return error;
 648         dentry = f->f_path.dentry;
 649         audit_inode(NULL, dentry);
 650         error = mnt_want_write_file(f);
 651         if (!error) {
 652                 error = removexattr(dentry, name);
 653                 mnt_drop_write_file(f);
 654         }
 655         fput_light(f, fput_needed);
 656         return error;
 657 }
 658
 659
 660 static const char *
 661 strcmp_prefix(const char *a, const char *a_prefix)
 662 {
 663         while (*a_prefix && *a == *a_prefix) {
 664                 a++;
 665                 a_prefix++;
 666         }
 667         return *a_prefix ? NULL : a;
 668 }
 669
 670 /*
 671  * In order to implement different sets of xattr operations for each xattr
 672  * prefix with the generic xattr API, a filesystem should create a
 673  * null-terminated array of struct xattr_handler (one for each prefix) and
 674  * hang a pointer to it off of the s_xattr field of the superblock.
 675  *
 676  * The generic_fooxattr() functions will use this list to dispatch xattr
 677  * operations to the correct xattr_handler.
 678  */
 679 #define for_each_xattr_handler(handlers, handler)               \
 680                 for ((handler) = *(handlers)++;                 \
 681                         (handler) != NULL;                      \
 682                         (handler) = *(handlers)++)
 683
 684 /*
 685  * Find the xattr_handler with the matching prefix.
 686  */
 687 static const struct xattr_handler *
 688 xattr_resolve_name(const struct xattr_handler **handlers, const char **name)
 689 {
 690         const struct xattr_handler *handler;
 691
 692         if (!*name)
 693                 return NULL;
 694
 695         for_each_xattr_handler(handlers, handler) {
 696                 const char *n = strcmp_prefix(*name, handler->prefix);
 697                 if (n) {
 698                         *name = n;
 699                         break;
 700                 }
 701         }
 702         return handler;
 703 }
 704
 705 /*
 706  * Find the handler for the prefix and dispatch its get() operation.
 707  */
 708 ssize_t
 709 generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size)
 710 {
 711         const struct xattr_handler *handler;
 712
 713         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 714         if (!handler)
 715                 return -EOPNOTSUPP;
 716         return handler->get(dentry, name, buffer, size, handler->flags);
 717 }
 718
 719 /*
 720  * Combine the results of the list() operation from every xattr_handler in the
 721  * list.
 722  */
 723 ssize_t
 724 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 725 {
 726         const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
 727         unsigned int size = 0;
 728
 729         if (!buffer) {
 730                 for_each_xattr_handler(handlers, handler) {
 731                         size += handler->list(dentry, NULL, 0, NULL, 0,
 732                                               handler->flags);
 733                 }
 734         } else {
 735                 char *buf = buffer;
 736
 737                 for_each_xattr_handler(handlers, handler) {
 738                         size = handler->list(dentry, buf, buffer_size,
 739                                              NULL, 0, handler->flags);
 740                         if (size > buffer_size)
 741                                 return -ERANGE;
 742                         buf += size;
 743                         buffer_size -= size;
 744                 }
 745                 size = buf - buffer;
 746         }
 747         return size;
 748 }
 749
 750 /*
 751  * Find the handler for the prefix and dispatch its set() operation.
 752  */
 753 int
 754 generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags)
 755 {
 756         const struct xattr_handler *handler;
 757
 758         if (size == 0)
 759                 value = "";  /* empty EA, do not remove */
 760         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 761         if (!handler)
 762                 return -EOPNOTSUPP;
 763         return handler->set(dentry, name, value, size, flags, handler->flags);
 764 }
 765
 766 /*
 767  * Find the handler for the prefix and dispatch its set() operation to remove
 768  * any associated extended attribute.
 769  */
 770 int
 771 generic_removexattr(struct dentry *dentry, const char *name)
 772 {
 773         const struct xattr_handler *handler;
 774
 775         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 776         if (!handler)
 777                 return -EOPNOTSUPP;
 778         return handler->set(dentry, name, NULL, 0,
 779                             XATTR_REPLACE, handler->flags);
 780 }
 781
 782 EXPORT_SYMBOL(generic_getxattr);
 783 EXPORT_SYMBOL(generic_listxattr);
 784 EXPORT_SYMBOL(generic_setxattr);
 785 EXPORT_SYMBOL(generic_removexattr);