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         void *vvalue = NULL;
 431         char kname[XATTR_NAME_MAX + 1];
 432
 433         error = strncpy_from_user(kname, name, sizeof(kname));
 434         if (error == 0 || error == sizeof(kname))
 435                 error = -ERANGE;
 436         if (error < 0)
 437                 return error;
 438
 439         if (size) {
 440                 if (size > XATTR_SIZE_MAX)
 441                         size = XATTR_SIZE_MAX;
 442                 kvalue = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
 443                 if (!kvalue) {
 444                         vvalue = vmalloc(size);
 445                         if (!vvalue)
 446                                 return -ENOMEM;
 447                         kvalue = vvalue;
 448                 }
 449         }
 450
 451         error = vfs_getxattr(d, kname, kvalue, size);
 452         if (error > 0) {
 453                 if (size && copy_to_user(value, kvalue, error))
 454                         error = -EFAULT;
 455         } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
 456                 /* The file system tried to returned a value bigger
 457                    than XATTR_SIZE_MAX bytes. Not possible. */
 458                 error = -E2BIG;
 459         }
 460         if (vvalue)
 461                 vfree(vvalue);
 462         else
 463                 kfree(kvalue);
 464         return error;
 465 }
 466
 467 SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
 468                 const char __user *, name, void __user *, value, size_t, size)
 469 {
 470         struct path path;
 471         ssize_t error;
 472
 473         error = user_path(pathname, &path);
 474         if (error)
 475                 return error;
 476         error = getxattr(path.dentry, name, value, size);
 477         path_put(&path);
 478         return error;
 479 }
 480
 481 SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
 482                 const char __user *, name, void __user *, value, size_t, size)
 483 {
 484         struct path path;
 485         ssize_t error;
 486
 487         error = user_lpath(pathname, &path);
 488         if (error)
 489                 return error;
 490         error = getxattr(path.dentry, name, value, size);
 491         path_put(&path);
 492         return error;
 493 }
 494
 495 SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
 496                 void __user *, value, size_t, size)
 497 {
 498         int fput_needed;
 499         struct file *f;
 500         ssize_t error = -EBADF;
 501
 502         f = fget_light(fd, &fput_needed);
 503         if (!f)
 504                 return error;
 505         audit_inode(NULL, f->f_path.dentry);
 506         error = getxattr(f->f_path.dentry, name, value, size);
 507         fput_light(f, fput_needed);
 508         return error;
 509 }
 510
 511 /*
 512  * Extended attribute LIST operations
 513  */
 514 static ssize_t
 515 listxattr(struct dentry *d, char __user *list, size_t size)
 516 {
 517         ssize_t error;
 518         char *klist = NULL;
 519         char *vlist = NULL;     /* If non-NULL, we used vmalloc() */
 520
 521         if (size) {
 522                 if (size > XATTR_LIST_MAX)
 523                         size = XATTR_LIST_MAX;
 524                 klist = kmalloc(size, __GFP_NOWARN | GFP_KERNEL);
 525                 if (!klist) {
 526                         vlist = vmalloc(size);
 527                         if (!vlist)
 528                                 return -ENOMEM;
 529                         klist = vlist;
 530                 }
 531         }
 532
 533         error = vfs_listxattr(d, klist, size);
 534         if (error > 0) {
 535                 if (size && copy_to_user(list, klist, error))
 536                         error = -EFAULT;
 537         } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
 538                 /* The file system tried to returned a list bigger
 539                    than XATTR_LIST_MAX bytes. Not possible. */
 540                 error = -E2BIG;
 541         }
 542         if (vlist)
 543                 vfree(vlist);
 544         else
 545                 kfree(klist);
 546         return error;
 547 }
 548
 549 SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
 550                 size_t, size)
 551 {
 552         struct path path;
 553         ssize_t error;
 554
 555         error = user_path(pathname, &path);
 556         if (error)
 557                 return error;
 558         error = listxattr(path.dentry, list, size);
 559         path_put(&path);
 560         return error;
 561 }
 562
 563 SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
 564                 size_t, size)
 565 {
 566         struct path path;
 567         ssize_t error;
 568
 569         error = user_lpath(pathname, &path);
 570         if (error)
 571                 return error;
 572         error = listxattr(path.dentry, list, size);
 573         path_put(&path);
 574         return error;
 575 }
 576
 577 SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
 578 {
 579         int fput_needed;
 580         struct file *f;
 581         ssize_t error = -EBADF;
 582
 583         f = fget_light(fd, &fput_needed);
 584         if (!f)
 585                 return error;
 586         audit_inode(NULL, f->f_path.dentry);
 587         error = listxattr(f->f_path.dentry, list, size);
 588         fput_light(f, fput_needed);
 589         return error;
 590 }
 591
 592 /*
 593  * Extended attribute REMOVE operations
 594  */
 595 static long
 596 removexattr(struct dentry *d, const char __user *name)
 597 {
 598         int error;
 599         char kname[XATTR_NAME_MAX + 1];
 600
 601         error = strncpy_from_user(kname, name, sizeof(kname));
 602         if (error == 0 || error == sizeof(kname))
 603                 error = -ERANGE;
 604         if (error < 0)
 605                 return error;
 606
 607         return vfs_removexattr(d, kname);
 608 }
 609
 610 SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
 611                 const char __user *, name)
 612 {
 613         struct path path;
 614         int error;
 615
 616         error = user_path(pathname, &path);
 617         if (error)
 618                 return error;
 619         error = mnt_want_write(path.mnt);
 620         if (!error) {
 621                 error = removexattr(path.dentry, name);
 622                 mnt_drop_write(path.mnt);
 623         }
 624         path_put(&path);
 625         return error;
 626 }
 627
 628 SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
 629                 const char __user *, name)
 630 {
 631         struct path path;
 632         int error;
 633
 634         error = user_lpath(pathname, &path);
 635         if (error)
 636                 return error;
 637         error = mnt_want_write(path.mnt);
 638         if (!error) {
 639                 error = removexattr(path.dentry, name);
 640                 mnt_drop_write(path.mnt);
 641         }
 642         path_put(&path);
 643         return error;
 644 }
 645
 646 SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
 647 {
 648         int fput_needed;
 649         struct file *f;
 650         struct dentry *dentry;
 651         int error = -EBADF;
 652
 653         f = fget_light(fd, &fput_needed);
 654         if (!f)
 655                 return error;
 656         dentry = f->f_path.dentry;
 657         audit_inode(NULL, dentry);
 658         error = mnt_want_write_file(f);
 659         if (!error) {
 660                 error = removexattr(dentry, name);
 661                 mnt_drop_write_file(f);
 662         }
 663         fput_light(f, fput_needed);
 664         return error;
 665 }
 666
 667
 668 static const char *
 669 strcmp_prefix(const char *a, const char *a_prefix)
 670 {
 671         while (*a_prefix && *a == *a_prefix) {
 672                 a++;
 673                 a_prefix++;
 674         }
 675         return *a_prefix ? NULL : a;
 676 }
 677
 678 /*
 679  * In order to implement different sets of xattr operations for each xattr
 680  * prefix with the generic xattr API, a filesystem should create a
 681  * null-terminated array of struct xattr_handler (one for each prefix) and
 682  * hang a pointer to it off of the s_xattr field of the superblock.
 683  *
 684  * The generic_fooxattr() functions will use this list to dispatch xattr
 685  * operations to the correct xattr_handler.
 686  */
 687 #define for_each_xattr_handler(handlers, handler)               \
 688                 for ((handler) = *(handlers)++;                 \
 689                         (handler) != NULL;                      \
 690                         (handler) = *(handlers)++)
 691
 692 /*
 693  * Find the xattr_handler with the matching prefix.
 694  */
 695 static const struct xattr_handler *
 696 xattr_resolve_name(const struct xattr_handler **handlers, const char **name)
 697 {
 698         const struct xattr_handler *handler;
 699
 700         if (!*name)
 701                 return NULL;
 702
 703         for_each_xattr_handler(handlers, handler) {
 704                 const char *n = strcmp_prefix(*name, handler->prefix);
 705                 if (n) {
 706                         *name = n;
 707                         break;
 708                 }
 709         }
 710         return handler;
 711 }
 712
 713 /*
 714  * Find the handler for the prefix and dispatch its get() operation.
 715  */
 716 ssize_t
 717 generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size)
 718 {
 719         const struct xattr_handler *handler;
 720
 721         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 722         if (!handler)
 723                 return -EOPNOTSUPP;
 724         return handler->get(dentry, name, buffer, size, handler->flags);
 725 }
 726
 727 /*
 728  * Combine the results of the list() operation from every xattr_handler in the
 729  * list.
 730  */
 731 ssize_t
 732 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 733 {
 734         const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
 735         unsigned int size = 0;
 736
 737         if (!buffer) {
 738                 for_each_xattr_handler(handlers, handler) {
 739                         size += handler->list(dentry, NULL, 0, NULL, 0,
 740                                               handler->flags);
 741                 }
 742         } else {
 743                 char *buf = buffer;
 744
 745                 for_each_xattr_handler(handlers, handler) {
 746                         size = handler->list(dentry, buf, buffer_size,
 747                                              NULL, 0, handler->flags);
 748                         if (size > buffer_size)
 749                                 return -ERANGE;
 750                         buf += size;
 751                         buffer_size -= size;
 752                 }
 753                 size = buf - buffer;
 754         }
 755         return size;
 756 }
 757
 758 /*
 759  * Find the handler for the prefix and dispatch its set() operation.
 760  */
 761 int
 762 generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags)
 763 {
 764         const struct xattr_handler *handler;
 765
 766         if (size == 0)
 767                 value = "";  /* empty EA, do not remove */
 768         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 769         if (!handler)
 770                 return -EOPNOTSUPP;
 771         return handler->set(dentry, name, value, size, flags, handler->flags);
 772 }
 773
 774 /*
 775  * Find the handler for the prefix and dispatch its set() operation to remove
 776  * any associated extended attribute.
 777  */
 778 int
 779 generic_removexattr(struct dentry *dentry, const char *name)
 780 {
 781         const struct xattr_handler *handler;
 782
 783         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 784         if (!handler)
 785                 return -EOPNOTSUPP;
 786         return handler->set(dentry, name, NULL, 0,
 787                             XATTR_REPLACE, handler->flags);
 788 }
 789
 790 EXPORT_SYMBOL(generic_getxattr);
 791 EXPORT_SYMBOL(generic_listxattr);
 792 EXPORT_SYMBOL(generic_setxattr);
 793 EXPORT_SYMBOL(generic_removexattr);