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         int fput_needed;
 407         struct file *f;
 408         struct dentry *dentry;
 409         int error = -EBADF;
 410
 411         f = fget_light(fd, &fput_needed);
 412         if (!f)
 413                 return error;
 414         dentry = f->f_path.dentry;
 415         audit_inode(NULL, dentry);
 416         error = mnt_want_write_file(f);
 417         if (!error) {
 418                 error = setxattr(dentry, name, value, size, flags);
 419                 mnt_drop_write_file(f);
 420         }
 421         fput_light(f, fput_needed);
 422         return error;
 423 }
 424
 425 /*
 426  * Extended attribute GET operations
 427  */
 428 static ssize_t
 429 getxattr(struct dentry *d, const char __user *name, void __user *value,
 430          size_t size)
 431 {
 432         ssize_t error;
 433         void *kvalue = NULL;
 434         void *vvalue = NULL;
 435         char kname[XATTR_NAME_MAX + 1];
 436
 437         error = strncpy_from_user(kname, name, sizeof(kname));
 438         if (error == 0 || error == sizeof(kname))
 439                 error = -ERANGE;
 440         if (error < 0)
 441                 return error;
 442
 443         if (size) {
 444                 if (size > XATTR_SIZE_MAX)
 445                         size = XATTR_SIZE_MAX;
 446                 kvalue = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
 447                 if (!kvalue) {
 448                         vvalue = vmalloc(size);
 449                         if (!vvalue)
 450                                 return -ENOMEM;
 451                         kvalue = vvalue;
 452                 }
 453         }
 454
 455         error = vfs_getxattr(d, kname, kvalue, size);
 456         if (error > 0) {
 457                 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
 458                     (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
 459                         posix_acl_fix_xattr_to_user(kvalue, size);
 460                 if (size && copy_to_user(value, kvalue, error))
 461                         error = -EFAULT;
 462         } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
 463                 /* The file system tried to returned a value bigger
 464                    than XATTR_SIZE_MAX bytes. Not possible. */
 465                 error = -E2BIG;
 466         }
 467         if (vvalue)
 468                 vfree(vvalue);
 469         else
 470                 kfree(kvalue);
 471         return error;
 472 }
 473
 474 SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
 475                 const char __user *, name, void __user *, value, size_t, size)
 476 {
 477         struct path path;
 478         ssize_t error;
 479
 480         error = user_path(pathname, &path);
 481         if (error)
 482                 return error;
 483         error = getxattr(path.dentry, name, value, size);
 484         path_put(&path);
 485         return error;
 486 }
 487
 488 SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
 489                 const char __user *, name, void __user *, value, size_t, size)
 490 {
 491         struct path path;
 492         ssize_t error;
 493
 494         error = user_lpath(pathname, &path);
 495         if (error)
 496                 return error;
 497         error = getxattr(path.dentry, name, value, size);
 498         path_put(&path);
 499         return error;
 500 }
 501
 502 SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
 503                 void __user *, value, size_t, size)
 504 {
 505         int fput_needed;
 506         struct file *f;
 507         ssize_t error = -EBADF;
 508
 509         f = fget_light(fd, &fput_needed);
 510         if (!f)
 511                 return error;
 512         audit_inode(NULL, f->f_path.dentry);
 513         error = getxattr(f->f_path.dentry, name, value, size);
 514         fput_light(f, fput_needed);
 515         return error;
 516 }
 517
 518 /*
 519  * Extended attribute LIST operations
 520  */
 521 static ssize_t
 522 listxattr(struct dentry *d, char __user *list, size_t size)
 523 {
 524         ssize_t error;
 525         char *klist = NULL;
 526         char *vlist = NULL;     /* If non-NULL, we used vmalloc() */
 527
 528         if (size) {
 529                 if (size > XATTR_LIST_MAX)
 530                         size = XATTR_LIST_MAX;
 531                 klist = kmalloc(size, __GFP_NOWARN | GFP_KERNEL);
 532                 if (!klist) {
 533                         vlist = vmalloc(size);
 534                         if (!vlist)
 535                                 return -ENOMEM;
 536                         klist = vlist;
 537                 }
 538         }
 539
 540         error = vfs_listxattr(d, klist, size);
 541         if (error > 0) {
 542                 if (size && copy_to_user(list, klist, error))
 543                         error = -EFAULT;
 544         } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
 545                 /* The file system tried to returned a list bigger
 546                    than XATTR_LIST_MAX bytes. Not possible. */
 547                 error = -E2BIG;
 548         }
 549         if (vlist)
 550                 vfree(vlist);
 551         else
 552                 kfree(klist);
 553         return error;
 554 }
 555
 556 SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
 557                 size_t, size)
 558 {
 559         struct path path;
 560         ssize_t error;
 561
 562         error = user_path(pathname, &path);
 563         if (error)
 564                 return error;
 565         error = listxattr(path.dentry, list, size);
 566         path_put(&path);
 567         return error;
 568 }
 569
 570 SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
 571                 size_t, size)
 572 {
 573         struct path path;
 574         ssize_t error;
 575
 576         error = user_lpath(pathname, &path);
 577         if (error)
 578                 return error;
 579         error = listxattr(path.dentry, list, size);
 580         path_put(&path);
 581         return error;
 582 }
 583
 584 SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
 585 {
 586         int fput_needed;
 587         struct file *f;
 588         ssize_t error = -EBADF;
 589
 590         f = fget_light(fd, &fput_needed);
 591         if (!f)
 592                 return error;
 593         audit_inode(NULL, f->f_path.dentry);
 594         error = listxattr(f->f_path.dentry, list, size);
 595         fput_light(f, fput_needed);
 596         return error;
 597 }
 598
 599 /*
 600  * Extended attribute REMOVE operations
 601  */
 602 static long
 603 removexattr(struct dentry *d, const char __user *name)
 604 {
 605         int error;
 606         char kname[XATTR_NAME_MAX + 1];
 607
 608         error = strncpy_from_user(kname, name, sizeof(kname));
 609         if (error == 0 || error == sizeof(kname))
 610                 error = -ERANGE;
 611         if (error < 0)
 612                 return error;
 613
 614         return vfs_removexattr(d, kname);
 615 }
 616
 617 SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
 618                 const char __user *, name)
 619 {
 620         struct path path;
 621         int error;
 622
 623         error = user_path(pathname, &path);
 624         if (error)
 625                 return error;
 626         error = mnt_want_write(path.mnt);
 627         if (!error) {
 628                 error = removexattr(path.dentry, name);
 629                 mnt_drop_write(path.mnt);
 630         }
 631         path_put(&path);
 632         return error;
 633 }
 634
 635 SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
 636                 const char __user *, name)
 637 {
 638         struct path path;
 639         int error;
 640
 641         error = user_lpath(pathname, &path);
 642         if (error)
 643                 return error;
 644         error = mnt_want_write(path.mnt);
 645         if (!error) {
 646                 error = removexattr(path.dentry, name);
 647                 mnt_drop_write(path.mnt);
 648         }
 649         path_put(&path);
 650         return error;
 651 }
 652
 653 SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
 654 {
 655         int fput_needed;
 656         struct file *f;
 657         struct dentry *dentry;
 658         int error = -EBADF;
 659
 660         f = fget_light(fd, &fput_needed);
 661         if (!f)
 662                 return error;
 663         dentry = f->f_path.dentry;
 664         audit_inode(NULL, dentry);
 665         error = mnt_want_write_file(f);
 666         if (!error) {
 667                 error = removexattr(dentry, name);
 668                 mnt_drop_write_file(f);
 669         }
 670         fput_light(f, fput_needed);
 671         return error;
 672 }
 673
 674
 675 static const char *
 676 strcmp_prefix(const char *a, const char *a_prefix)
 677 {
 678         while (*a_prefix && *a == *a_prefix) {
 679                 a++;
 680                 a_prefix++;
 681         }
 682         return *a_prefix ? NULL : a;
 683 }
 684
 685 /*
 686  * In order to implement different sets of xattr operations for each xattr
 687  * prefix with the generic xattr API, a filesystem should create a
 688  * null-terminated array of struct xattr_handler (one for each prefix) and
 689  * hang a pointer to it off of the s_xattr field of the superblock.
 690  *
 691  * The generic_fooxattr() functions will use this list to dispatch xattr
 692  * operations to the correct xattr_handler.
 693  */
 694 #define for_each_xattr_handler(handlers, handler)               \
 695                 for ((handler) = *(handlers)++;                 \
 696                         (handler) != NULL;                      \
 697                         (handler) = *(handlers)++)
 698
 699 /*
 700  * Find the xattr_handler with the matching prefix.
 701  */
 702 static const struct xattr_handler *
 703 xattr_resolve_name(const struct xattr_handler **handlers, const char **name)
 704 {
 705         const struct xattr_handler *handler;
 706
 707         if (!*name)
 708                 return NULL;
 709
 710         for_each_xattr_handler(handlers, handler) {
 711                 const char *n = strcmp_prefix(*name, handler->prefix);
 712                 if (n) {
 713                         *name = n;
 714                         break;
 715                 }
 716         }
 717         return handler;
 718 }
 719
 720 /*
 721  * Find the handler for the prefix and dispatch its get() operation.
 722  */
 723 ssize_t
 724 generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size)
 725 {
 726         const struct xattr_handler *handler;
 727
 728         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 729         if (!handler)
 730                 return -EOPNOTSUPP;
 731         return handler->get(dentry, name, buffer, size, handler->flags);
 732 }
 733
 734 /*
 735  * Combine the results of the list() operation from every xattr_handler in the
 736  * list.
 737  */
 738 ssize_t
 739 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 740 {
 741         const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
 742         unsigned int size = 0;
 743
 744         if (!buffer) {
 745                 for_each_xattr_handler(handlers, handler) {
 746                         size += handler->list(dentry, NULL, 0, NULL, 0,
 747                                               handler->flags);
 748                 }
 749         } else {
 750                 char *buf = buffer;
 751
 752                 for_each_xattr_handler(handlers, handler) {
 753                         size = handler->list(dentry, buf, buffer_size,
 754                                              NULL, 0, handler->flags);
 755                         if (size > buffer_size)
 756                                 return -ERANGE;
 757                         buf += size;
 758                         buffer_size -= size;
 759                 }
 760                 size = buf - buffer;
 761         }
 762         return size;
 763 }
 764
 765 /*
 766  * Find the handler for the prefix and dispatch its set() operation.
 767  */
 768 int
 769 generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags)
 770 {
 771         const struct xattr_handler *handler;
 772
 773         if (size == 0)
 774                 value = "";  /* empty EA, do not remove */
 775         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 776         if (!handler)
 777                 return -EOPNOTSUPP;
 778         return handler->set(dentry, name, value, size, flags, handler->flags);
 779 }
 780
 781 /*
 782  * Find the handler for the prefix and dispatch its set() operation to remove
 783  * any associated extended attribute.
 784  */
 785 int
 786 generic_removexattr(struct dentry *dentry, const char *name)
 787 {
 788         const struct xattr_handler *handler;
 789
 790         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 791         if (!handler)
 792                 return -EOPNOTSUPP;
 793         return handler->set(dentry, name, NULL, 0,
 794                             XATTR_REPLACE, handler->flags);
 795 }
 796
 797 EXPORT_SYMBOL(generic_getxattr);
 798 EXPORT_SYMBOL(generic_listxattr);
 799 EXPORT_SYMBOL(generic_setxattr);
 800 EXPORT_SYMBOL(generic_removexattr);