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         mutex_lock(&inode->i_mutex);
 299         error = security_inode_removexattr(dentry, name);
 300         if (error) {
 301                 mutex_unlock(&inode->i_mutex);
 302                 return error;
 303         }
 304
 305         error = inode->i_op->removexattr(dentry, name);
 306         mutex_unlock(&inode->i_mutex);
 307
 308         if (!error) {
 309                 fsnotify_xattr(dentry);
 310                 evm_inode_post_removexattr(dentry, name);
 311         }
 312         return error;
 313 }
 314 EXPORT_SYMBOL_GPL(vfs_removexattr);
 315
 316
 317 /*
 318  * Extended attribute SET operations
 319  */
 320 static long
 321 setxattr(struct dentry *d, const char __user *name, const void __user *value,
 322          size_t size, int flags)
 323 {
 324         int error;
 325         void *kvalue = NULL;
 326         void *vvalue = NULL;    /* If non-NULL, we used vmalloc() */
 327         char kname[XATTR_NAME_MAX + 1];
 328
 329         if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
 330                 return -EINVAL;
 331
 332         error = strncpy_from_user(kname, name, sizeof(kname));
 333         if (error == 0 || error == sizeof(kname))
 334                 error = -ERANGE;
 335         if (error < 0)
 336                 return error;
 337
 338         if (size) {
 339                 if (size > XATTR_SIZE_MAX)
 340                         return -E2BIG;
 341                 kvalue = kmalloc(size, GFP_KERNEL | __GFP_NOWARN);
 342                 if (!kvalue) {
 343                         vvalue = vmalloc(size);
 344                         if (!vvalue)
 345                                 return -ENOMEM;
 346                         kvalue = vvalue;
 347                 }
 348                 if (copy_from_user(kvalue, value, size)) {
 349                         error = -EFAULT;
 350                         goto out;
 351                 }
 352         }
 353
 354         error = vfs_setxattr(d, kname, kvalue, size, flags);
 355 out:
 356         if (vvalue)
 357                 vfree(vvalue);
 358         else
 359                 kfree(kvalue);
 360         return error;
 361 }
 362
 363 SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
 364                 const char __user *, name, const void __user *, value,
 365                 size_t, size, int, flags)
 366 {
 367         struct path path;
 368         int error;
 369
 370         error = user_path(pathname, &path);
 371         if (error)
 372                 return error;
 373         error = mnt_want_write(path.mnt);
 374         if (!error) {
 375                 error = setxattr(path.dentry, name, value, size, flags);
 376                 mnt_drop_write(path.mnt);
 377         }
 378         path_put(&path);
 379         return error;
 380 }
 381
 382 SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
 383                 const char __user *, name, const void __user *, value,
 384                 size_t, size, int, flags)
 385 {
 386         struct path path;
 387         int error;
 388
 389         error = user_lpath(pathname, &path);
 390         if (error)
 391                 return error;
 392         error = mnt_want_write(path.mnt);
 393         if (!error) {
 394                 error = setxattr(path.dentry, name, value, size, flags);
 395                 mnt_drop_write(path.mnt);
 396         }
 397         path_put(&path);
 398         return error;
 399 }
 400
 401 SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
 402                 const void __user *,value, size_t, size, int, flags)
 403 {
 404         int fput_needed;
 405         struct file *f;
 406         struct dentry *dentry;
 407         int error = -EBADF;
 408
 409         f = fget_light(fd, &fput_needed);
 410         if (!f)
 411                 return error;
 412         dentry = f->f_path.dentry;
 413         audit_inode(NULL, dentry);
 414         error = mnt_want_write_file(f);
 415         if (!error) {
 416                 error = setxattr(dentry, name, value, size, flags);
 417                 mnt_drop_write_file(f);
 418         }
 419         fput_light(f, fput_needed);
 420         return error;
 421 }
 422
 423 /*
 424  * Extended attribute GET operations
 425  */
 426 static ssize_t
 427 getxattr(struct dentry *d, const char __user *name, void __user *value,
 428          size_t size)
 429 {
 430         ssize_t error;
 431         void *kvalue = NULL;
 432         void *vvalue = NULL;
 433         char kname[XATTR_NAME_MAX + 1];
 434
 435         error = strncpy_from_user(kname, name, sizeof(kname));
 436         if (error == 0 || error == sizeof(kname))
 437                 error = -ERANGE;
 438         if (error < 0)
 439                 return error;
 440
 441         if (size) {
 442                 if (size > XATTR_SIZE_MAX)
 443                         size = XATTR_SIZE_MAX;
 444                 kvalue = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
 445                 if (!kvalue) {
 446                         vvalue = vmalloc(size);
 447                         if (!vvalue)
 448                                 return -ENOMEM;
 449                         kvalue = vvalue;
 450                 }
 451         }
 452
 453         error = vfs_getxattr(d, kname, kvalue, size);
 454         if (error > 0) {
 455                 if (size && copy_to_user(value, kvalue, error))
 456                         error = -EFAULT;
 457         } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
 458                 /* The file system tried to returned a value bigger
 459                    than XATTR_SIZE_MAX bytes. Not possible. */
 460                 error = -E2BIG;
 461         }
 462         if (vvalue)
 463                 vfree(vvalue);
 464         else
 465                 kfree(kvalue);
 466         return error;
 467 }
 468
 469 SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
 470                 const char __user *, name, void __user *, value, size_t, size)
 471 {
 472         struct path path;
 473         ssize_t error;
 474
 475         error = user_path(pathname, &path);
 476         if (error)
 477                 return error;
 478         error = getxattr(path.dentry, name, value, size);
 479         path_put(&path);
 480         return error;
 481 }
 482
 483 SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
 484                 const char __user *, name, void __user *, value, size_t, size)
 485 {
 486         struct path path;
 487         ssize_t error;
 488
 489         error = user_lpath(pathname, &path);
 490         if (error)
 491                 return error;
 492         error = getxattr(path.dentry, name, value, size);
 493         path_put(&path);
 494         return error;
 495 }
 496
 497 SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
 498                 void __user *, value, size_t, size)
 499 {
 500         int fput_needed;
 501         struct file *f;
 502         ssize_t error = -EBADF;
 503
 504         f = fget_light(fd, &fput_needed);
 505         if (!f)
 506                 return error;
 507         audit_inode(NULL, f->f_path.dentry);
 508         error = getxattr(f->f_path.dentry, name, value, size);
 509         fput_light(f, fput_needed);
 510         return error;
 511 }
 512
 513 /*
 514  * Extended attribute LIST operations
 515  */
 516 static ssize_t
 517 listxattr(struct dentry *d, char __user *list, size_t size)
 518 {
 519         ssize_t error;
 520         char *klist = NULL;
 521         char *vlist = NULL;     /* If non-NULL, we used vmalloc() */
 522
 523         if (size) {
 524                 if (size > XATTR_LIST_MAX)
 525                         size = XATTR_LIST_MAX;
 526                 klist = kmalloc(size, __GFP_NOWARN | GFP_KERNEL);
 527                 if (!klist) {
 528                         vlist = vmalloc(size);
 529                         if (!vlist)
 530                                 return -ENOMEM;
 531                         klist = vlist;
 532                 }
 533         }
 534
 535         error = vfs_listxattr(d, klist, size);
 536         if (error > 0) {
 537                 if (size && copy_to_user(list, klist, error))
 538                         error = -EFAULT;
 539         } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
 540                 /* The file system tried to returned a list bigger
 541                    than XATTR_LIST_MAX bytes. Not possible. */
 542                 error = -E2BIG;
 543         }
 544         if (vlist)
 545                 vfree(vlist);
 546         else
 547                 kfree(klist);
 548         return error;
 549 }
 550
 551 SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
 552                 size_t, size)
 553 {
 554         struct path path;
 555         ssize_t error;
 556
 557         error = user_path(pathname, &path);
 558         if (error)
 559                 return error;
 560         error = listxattr(path.dentry, list, size);
 561         path_put(&path);
 562         return error;
 563 }
 564
 565 SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
 566                 size_t, size)
 567 {
 568         struct path path;
 569         ssize_t error;
 570
 571         error = user_lpath(pathname, &path);
 572         if (error)
 573                 return error;
 574         error = listxattr(path.dentry, list, size);
 575         path_put(&path);
 576         return error;
 577 }
 578
 579 SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
 580 {
 581         int fput_needed;
 582         struct file *f;
 583         ssize_t error = -EBADF;
 584
 585         f = fget_light(fd, &fput_needed);
 586         if (!f)
 587                 return error;
 588         audit_inode(NULL, f->f_path.dentry);
 589         error = listxattr(f->f_path.dentry, list, size);
 590         fput_light(f, fput_needed);
 591         return error;
 592 }
 593
 594 /*
 595  * Extended attribute REMOVE operations
 596  */
 597 static long
 598 removexattr(struct dentry *d, const char __user *name)
 599 {
 600         int error;
 601         char kname[XATTR_NAME_MAX + 1];
 602
 603         error = strncpy_from_user(kname, name, sizeof(kname));
 604         if (error == 0 || error == sizeof(kname))
 605                 error = -ERANGE;
 606         if (error < 0)
 607                 return error;
 608
 609         return vfs_removexattr(d, kname);
 610 }
 611
 612 SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
 613                 const char __user *, name)
 614 {
 615         struct path path;
 616         int error;
 617
 618         error = user_path(pathname, &path);
 619         if (error)
 620                 return error;
 621         error = mnt_want_write(path.mnt);
 622         if (!error) {
 623                 error = removexattr(path.dentry, name);
 624                 mnt_drop_write(path.mnt);
 625         }
 626         path_put(&path);
 627         return error;
 628 }
 629
 630 SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
 631                 const char __user *, name)
 632 {
 633         struct path path;
 634         int error;
 635
 636         error = user_lpath(pathname, &path);
 637         if (error)
 638                 return error;
 639         error = mnt_want_write(path.mnt);
 640         if (!error) {
 641                 error = removexattr(path.dentry, name);
 642                 mnt_drop_write(path.mnt);
 643         }
 644         path_put(&path);
 645         return error;
 646 }
 647
 648 SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
 649 {
 650         int fput_needed;
 651         struct file *f;
 652         struct dentry *dentry;
 653         int error = -EBADF;
 654
 655         f = fget_light(fd, &fput_needed);
 656         if (!f)
 657                 return error;
 658         dentry = f->f_path.dentry;
 659         audit_inode(NULL, dentry);
 660         error = mnt_want_write_file(f);
 661         if (!error) {
 662                 error = removexattr(dentry, name);
 663                 mnt_drop_write_file(f);
 664         }
 665         fput_light(f, fput_needed);
 666         return error;
 667 }
 668
 669
 670 static const char *
 671 strcmp_prefix(const char *a, const char *a_prefix)
 672 {
 673         while (*a_prefix && *a == *a_prefix) {
 674                 a++;
 675                 a_prefix++;
 676         }
 677         return *a_prefix ? NULL : a;
 678 }
 679
 680 /*
 681  * In order to implement different sets of xattr operations for each xattr
 682  * prefix with the generic xattr API, a filesystem should create a
 683  * null-terminated array of struct xattr_handler (one for each prefix) and
 684  * hang a pointer to it off of the s_xattr field of the superblock.
 685  *
 686  * The generic_fooxattr() functions will use this list to dispatch xattr
 687  * operations to the correct xattr_handler.
 688  */
 689 #define for_each_xattr_handler(handlers, handler)               \
 690                 for ((handler) = *(handlers)++;                 \
 691                         (handler) != NULL;                      \
 692                         (handler) = *(handlers)++)
 693
 694 /*
 695  * Find the xattr_handler with the matching prefix.
 696  */
 697 static const struct xattr_handler *
 698 xattr_resolve_name(const struct xattr_handler **handlers, const char **name)
 699 {
 700         const struct xattr_handler *handler;
 701
 702         if (!*name)
 703                 return NULL;
 704
 705         for_each_xattr_handler(handlers, handler) {
 706                 const char *n = strcmp_prefix(*name, handler->prefix);
 707                 if (n) {
 708                         *name = n;
 709                         break;
 710                 }
 711         }
 712         return handler;
 713 }
 714
 715 /*
 716  * Find the handler for the prefix and dispatch its get() operation.
 717  */
 718 ssize_t
 719 generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size)
 720 {
 721         const struct xattr_handler *handler;
 722
 723         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 724         if (!handler)
 725                 return -EOPNOTSUPP;
 726         return handler->get(dentry, name, buffer, size, handler->flags);
 727 }
 728
 729 /*
 730  * Combine the results of the list() operation from every xattr_handler in the
 731  * list.
 732  */
 733 ssize_t
 734 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 735 {
 736         const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
 737         unsigned int size = 0;
 738
 739         if (!buffer) {
 740                 for_each_xattr_handler(handlers, handler) {
 741                         size += handler->list(dentry, NULL, 0, NULL, 0,
 742                                               handler->flags);
 743                 }
 744         } else {
 745                 char *buf = buffer;
 746
 747                 for_each_xattr_handler(handlers, handler) {
 748                         size = handler->list(dentry, buf, buffer_size,
 749                                              NULL, 0, handler->flags);
 750                         if (size > buffer_size)
 751                                 return -ERANGE;
 752                         buf += size;
 753                         buffer_size -= size;
 754                 }
 755                 size = buf - buffer;
 756         }
 757         return size;
 758 }
 759
 760 /*
 761  * Find the handler for the prefix and dispatch its set() operation.
 762  */
 763 int
 764 generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags)
 765 {
 766         const struct xattr_handler *handler;
 767
 768         if (size == 0)
 769                 value = "";  /* empty EA, do not remove */
 770         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 771         if (!handler)
 772                 return -EOPNOTSUPP;
 773         return handler->set(dentry, name, value, size, flags, handler->flags);
 774 }
 775
 776 /*
 777  * Find the handler for the prefix and dispatch its set() operation to remove
 778  * any associated extended attribute.
 779  */
 780 int
 781 generic_removexattr(struct dentry *dentry, const char *name)
 782 {
 783         const struct xattr_handler *handler;
 784
 785         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 786         if (!handler)
 787                 return -EOPNOTSUPP;
 788         return handler->set(dentry, name, NULL, 0,
 789                             XATTR_REPLACE, handler->flags);
 790 }
 791
 792 EXPORT_SYMBOL(generic_getxattr);
 793 EXPORT_SYMBOL(generic_listxattr);
 794 EXPORT_SYMBOL(generic_setxattr);
 795 EXPORT_SYMBOL(generic_removexattr);