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                  * Updating an xattr will likely cause i_uid and i_gid
  43                  * to be writen back improperly if their true value is
  44                  * unknown to the vfs.
  45                  */
  46                 if (HAS_UNMAPPED_ID(inode))
  47                         return -EPERM;
  48         }
  49
  50         /*
  51          * No restriction for security.* and system.* from the VFS.  Decision
  52          * on these is left to the underlying filesystem / security module.
  53          */
  54         if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||
  55             !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
  56                 return 0;
  57
  58         /*
  59          * The trusted.* namespace can only be accessed by privileged users.
  60          */
  61         if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
  62                 if (!capable(CAP_SYS_ADMIN))
  63                         return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
  64                 return 0;
  65         }
  66
  67         /*
  68          * In the user.* namespace, only regular files and directories can have
  69          * extended attributes. For sticky directories, only the owner and
  70          * privileged users can write attributes.
  71          */
  72         if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
  73                 if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
  74                         return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
  75                 if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&
  76                     (mask & MAY_WRITE) && !inode_owner_or_capable(inode))
  77                         return -EPERM;
  78         }
  79
  80         return inode_permission(inode, mask);
  81 }
  82
  83 /**
  84  *  __vfs_setxattr_noperm - perform setxattr operation without performing
  85  *  permission checks.
  86  *
  87  *  @dentry - object to perform setxattr on
  88  *  @name - xattr name to set
  89  *  @value - value to set @name to
  90  *  @size - size of @value
  91  *  @flags - flags to pass into filesystem operations
  92  *
  93  *  returns the result of the internal setxattr or setsecurity operations.
  94  *
  95  *  This function requires the caller to lock the inode's i_mutex before it
  96  *  is executed. It also assumes that the caller will make the appropriate
  97  *  permission checks.
  98  */
  99 int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
 100                 const void *value, size_t size, int flags)
 101 {
 102         struct inode *inode = dentry->d_inode;
 103         int error = -EOPNOTSUPP;
 104         int issec = !strncmp(name, XATTR_SECURITY_PREFIX,
 105                                    XATTR_SECURITY_PREFIX_LEN);
 106
 107         if (issec)
 108                 inode->i_flags &= ~S_NOSEC;
 109         if (inode->i_op->setxattr) {
 110                 error = inode->i_op->setxattr(dentry, inode, name, value, size, flags);
 111                 if (!error) {
 112                         fsnotify_xattr(dentry);
 113                         security_inode_post_setxattr(dentry, name, value,
 114                                                      size, flags);
 115                 }
 116         } else if (issec) {
 117                 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
 118                 error = security_inode_setsecurity(inode, suffix, value,
 119                                                    size, flags);
 120                 if (!error)
 121                         fsnotify_xattr(dentry);
 122         }
 123
 124         return error;
 125 }
 126
 127
 128 int
 129 vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
 130                 size_t size, int flags)
 131 {
 132         struct inode *inode = dentry->d_inode;
 133         int error;
 134
 135         error = xattr_permission(inode, name, MAY_WRITE);
 136         if (error)
 137                 return error;
 138
 139         inode_lock(inode);
 140         error = security_inode_setxattr(dentry, name, value, size, flags);
 141         if (error)
 142                 goto out;
 143
 144         error = __vfs_setxattr_noperm(dentry, name, value, size, flags);
 145
 146 out:
 147         inode_unlock(inode);
 148         return error;
 149 }
 150 EXPORT_SYMBOL_GPL(vfs_setxattr);
 151
 152 ssize_t
 153 xattr_getsecurity(struct inode *inode, const char *name, void *value,
 154                         size_t size)
 155 {
 156         void *buffer = NULL;
 157         ssize_t len;
 158
 159         if (!value || !size) {
 160                 len = security_inode_getsecurity(inode, name, &buffer, false);
 161                 goto out_noalloc;
 162         }
 163
 164         len = security_inode_getsecurity(inode, name, &buffer, true);
 165         if (len < 0)
 166                 return len;
 167         if (size < len) {
 168                 len = -ERANGE;
 169                 goto out;
 170         }
 171         memcpy(value, buffer, len);
 172 out:
 173         security_release_secctx(buffer, len);
 174 out_noalloc:
 175         return len;
 176 }
 177 EXPORT_SYMBOL_GPL(xattr_getsecurity);
 178
 179 /*
 180  * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
 181  *
 182  * Allocate memory, if not already allocated, or re-allocate correct size,
 183  * before retrieving the extended attribute.
 184  *
 185  * Returns the result of alloc, if failed, or the getxattr operation.
 186  */
 187 ssize_t
 188 vfs_getxattr_alloc(struct dentry *dentry, const char *name, char **xattr_value,
 189                    size_t xattr_size, gfp_t flags)
 190 {
 191         struct inode *inode = dentry->d_inode;
 192         char *value = *xattr_value;
 193         int error;
 194
 195         error = xattr_permission(inode, name, MAY_READ);
 196         if (error)
 197                 return error;
 198
 199         if (!inode->i_op->getxattr)
 200                 return -EOPNOTSUPP;
 201
 202         error = inode->i_op->getxattr(dentry, inode, name, NULL, 0);
 203         if (error < 0)
 204                 return error;
 205
 206         if (!value || (error > xattr_size)) {
 207                 value = krealloc(*xattr_value, error + 1, flags);
 208                 if (!value)
 209                         return -ENOMEM;
 210                 memset(value, 0, error + 1);
 211         }
 212
 213         error = inode->i_op->getxattr(dentry, inode, name, value, error);
 214         *xattr_value = value;
 215         return error;
 216 }
 217
 218 ssize_t
 219 vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
 220 {
 221         struct inode *inode = dentry->d_inode;
 222         int error;
 223
 224         error = xattr_permission(inode, name, MAY_READ);
 225         if (error)
 226                 return error;
 227
 228         error = security_inode_getxattr(dentry, name);
 229         if (error)
 230                 return error;
 231
 232         if (!strncmp(name, XATTR_SECURITY_PREFIX,
 233                                 XATTR_SECURITY_PREFIX_LEN)) {
 234                 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
 235                 int ret = xattr_getsecurity(inode, suffix, value, size);
 236                 /*
 237                  * Only overwrite the return value if a security module
 238                  * is actually active.
 239                  */
 240                 if (ret == -EOPNOTSUPP)
 241                         goto nolsm;
 242                 return ret;
 243         }
 244 nolsm:
 245         if (inode->i_op->getxattr)
 246                 error = inode->i_op->getxattr(dentry, inode, name, value, size);
 247         else
 248                 error = -EOPNOTSUPP;
 249
 250         return error;
 251 }
 252 EXPORT_SYMBOL_GPL(vfs_getxattr);
 253
 254 ssize_t
 255 vfs_listxattr(struct dentry *d, char *list, size_t size)
 256 {
 257         ssize_t error;
 258
 259         error = security_inode_listxattr(d);
 260         if (error)
 261                 return error;
 262         error = -EOPNOTSUPP;
 263         if (d->d_inode->i_op->listxattr) {
 264                 error = d->d_inode->i_op->listxattr(d, list, size);
 265         } else {
 266                 error = security_inode_listsecurity(d->d_inode, list, size);
 267                 if (size && error > size)
 268                         error = -ERANGE;
 269         }
 270         return error;
 271 }
 272 EXPORT_SYMBOL_GPL(vfs_listxattr);
 273
 274 int
 275 vfs_removexattr(struct dentry *dentry, const char *name)
 276 {
 277         struct inode *inode = dentry->d_inode;
 278         int error;
 279
 280         if (!inode->i_op->removexattr)
 281                 return -EOPNOTSUPP;
 282
 283         error = xattr_permission(inode, name, MAY_WRITE);
 284         if (error)
 285                 return error;
 286
 287         inode_lock(inode);
 288         error = security_inode_removexattr(dentry, name);
 289         if (error)
 290                 goto out;
 291
 292         error = inode->i_op->removexattr(dentry, name);
 293
 294         if (!error) {
 295                 fsnotify_xattr(dentry);
 296                 evm_inode_post_removexattr(dentry, name);
 297         }
 298
 299 out:
 300         inode_unlock(inode);
 301         return error;
 302 }
 303 EXPORT_SYMBOL_GPL(vfs_removexattr);
 304
 305
 306 /*
 307  * Extended attribute SET operations
 308  */
 309 static long
 310 setxattr(struct dentry *d, const char __user *name, const void __user *value,
 311          size_t size, int flags)
 312 {
 313         int error;
 314         void *kvalue = NULL;
 315         char kname[XATTR_NAME_MAX + 1];
 316
 317         if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
 318                 return -EINVAL;
 319
 320         error = strncpy_from_user(kname, name, sizeof(kname));
 321         if (error == 0 || error == sizeof(kname))
 322                 error = -ERANGE;
 323         if (error < 0)
 324                 return error;
 325
 326         if (size) {
 327                 if (size > XATTR_SIZE_MAX)
 328                         return -E2BIG;
 329                 kvalue = kmalloc(size, GFP_KERNEL | __GFP_NOWARN);
 330                 if (!kvalue) {
 331                         kvalue = vmalloc(size);
 332                         if (!kvalue)
 333                                 return -ENOMEM;
 334                 }
 335                 if (copy_from_user(kvalue, value, size)) {
 336                         error = -EFAULT;
 337                         goto out;
 338                 }
 339                 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
 340                     (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
 341                         posix_acl_fix_xattr_from_user(kvalue, size);
 342         }
 343
 344         error = vfs_setxattr(d, kname, kvalue, size, flags);
 345 out:
 346         kvfree(kvalue);
 347
 348         return error;
 349 }
 350
 351 static int path_setxattr(const char __user *pathname,
 352                          const char __user *name, const void __user *value,
 353                          size_t size, int flags, unsigned int lookup_flags)
 354 {
 355         struct path path;
 356         int error;
 357 retry:
 358         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 359         if (error)
 360                 return error;
 361         error = mnt_want_write(path.mnt);
 362         if (!error) {
 363                 error = setxattr(path.dentry, name, value, size, flags);
 364                 mnt_drop_write(path.mnt);
 365         }
 366         path_put(&path);
 367         if (retry_estale(error, lookup_flags)) {
 368                 lookup_flags |= LOOKUP_REVAL;
 369                 goto retry;
 370         }
 371         return error;
 372 }
 373
 374 SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
 375                 const char __user *, name, const void __user *, value,
 376                 size_t, size, int, flags)
 377 {
 378         return path_setxattr(pathname, name, value, size, flags, LOOKUP_FOLLOW);
 379 }
 380
 381 SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
 382                 const char __user *, name, const void __user *, value,
 383                 size_t, size, int, flags)
 384 {
 385         return path_setxattr(pathname, name, value, size, flags, 0);
 386 }
 387
 388 SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
 389                 const void __user *,value, size_t, size, int, flags)
 390 {
 391         struct fd f = fdget(fd);
 392         int error = -EBADF;
 393
 394         if (!f.file)
 395                 return error;
 396         audit_file(f.file);
 397         error = mnt_want_write_file(f.file);
 398         if (!error) {
 399                 error = setxattr(f.file->f_path.dentry, name, value, size, flags);
 400                 mnt_drop_write_file(f.file);
 401         }
 402         fdput(f);
 403         return error;
 404 }
 405
 406 /*
 407  * Extended attribute GET operations
 408  */
 409 static ssize_t
 410 getxattr(struct dentry *d, const char __user *name, void __user *value,
 411          size_t size)
 412 {
 413         ssize_t error;
 414         void *kvalue = NULL;
 415         char kname[XATTR_NAME_MAX + 1];
 416
 417         error = strncpy_from_user(kname, name, sizeof(kname));
 418         if (error == 0 || error == sizeof(kname))
 419                 error = -ERANGE;
 420         if (error < 0)
 421                 return error;
 422
 423         if (size) {
 424                 if (size > XATTR_SIZE_MAX)
 425                         size = XATTR_SIZE_MAX;
 426                 kvalue = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
 427                 if (!kvalue) {
 428                         kvalue = vmalloc(size);
 429                         if (!kvalue)
 430                                 return -ENOMEM;
 431                 }
 432         }
 433
 434         error = vfs_getxattr(d, kname, kvalue, size);
 435         if (error > 0) {
 436                 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
 437                     (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
 438                         posix_acl_fix_xattr_to_user(kvalue, size);
 439                 if (size && copy_to_user(value, kvalue, error))
 440                         error = -EFAULT;
 441         } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
 442                 /* The file system tried to returned a value bigger
 443                    than XATTR_SIZE_MAX bytes. Not possible. */
 444                 error = -E2BIG;
 445         }
 446
 447         kvfree(kvalue);
 448
 449         return error;
 450 }
 451
 452 static ssize_t path_getxattr(const char __user *pathname,
 453                              const char __user *name, void __user *value,
 454                              size_t size, unsigned int lookup_flags)
 455 {
 456         struct path path;
 457         ssize_t error;
 458 retry:
 459         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 460         if (error)
 461                 return error;
 462         error = getxattr(path.dentry, name, value, size);
 463         path_put(&path);
 464         if (retry_estale(error, lookup_flags)) {
 465                 lookup_flags |= LOOKUP_REVAL;
 466                 goto retry;
 467         }
 468         return error;
 469 }
 470
 471 SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
 472                 const char __user *, name, void __user *, value, size_t, size)
 473 {
 474         return path_getxattr(pathname, name, value, size, LOOKUP_FOLLOW);
 475 }
 476
 477 SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
 478                 const char __user *, name, void __user *, value, size_t, size)
 479 {
 480         return path_getxattr(pathname, name, value, size, 0);
 481 }
 482
 483 SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
 484                 void __user *, value, size_t, size)
 485 {
 486         struct fd f = fdget(fd);
 487         ssize_t error = -EBADF;
 488
 489         if (!f.file)
 490                 return error;
 491         audit_file(f.file);
 492         error = getxattr(f.file->f_path.dentry, name, value, size);
 493         fdput(f);
 494         return error;
 495 }
 496
 497 /*
 498  * Extended attribute LIST operations
 499  */
 500 static ssize_t
 501 listxattr(struct dentry *d, char __user *list, size_t size)
 502 {
 503         ssize_t error;
 504         char *klist = NULL;
 505
 506         if (size) {
 507                 if (size > XATTR_LIST_MAX)
 508                         size = XATTR_LIST_MAX;
 509                 klist = kmalloc(size, __GFP_NOWARN | GFP_KERNEL);
 510                 if (!klist) {
 511                         klist = vmalloc(size);
 512                         if (!klist)
 513                                 return -ENOMEM;
 514                 }
 515         }
 516
 517         error = vfs_listxattr(d, klist, size);
 518         if (error > 0) {
 519                 if (size && copy_to_user(list, klist, error))
 520                         error = -EFAULT;
 521         } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
 522                 /* The file system tried to returned a list bigger
 523                    than XATTR_LIST_MAX bytes. Not possible. */
 524                 error = -E2BIG;
 525         }
 526
 527         kvfree(klist);
 528
 529         return error;
 530 }
 531
 532 static ssize_t path_listxattr(const char __user *pathname, char __user *list,
 533                               size_t size, unsigned int lookup_flags)
 534 {
 535         struct path path;
 536         ssize_t error;
 537 retry:
 538         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 539         if (error)
 540                 return error;
 541         error = listxattr(path.dentry, list, size);
 542         path_put(&path);
 543         if (retry_estale(error, lookup_flags)) {
 544                 lookup_flags |= LOOKUP_REVAL;
 545                 goto retry;
 546         }
 547         return error;
 548 }
 549
 550 SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
 551                 size_t, size)
 552 {
 553         return path_listxattr(pathname, list, size, LOOKUP_FOLLOW);
 554 }
 555
 556 SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
 557                 size_t, size)
 558 {
 559         return path_listxattr(pathname, list, size, 0);
 560 }
 561
 562 SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
 563 {
 564         struct fd f = fdget(fd);
 565         ssize_t error = -EBADF;
 566
 567         if (!f.file)
 568                 return error;
 569         audit_file(f.file);
 570         error = listxattr(f.file->f_path.dentry, list, size);
 571         fdput(f);
 572         return error;
 573 }
 574
 575 /*
 576  * Extended attribute REMOVE operations
 577  */
 578 static long
 579 removexattr(struct dentry *d, const char __user *name)
 580 {
 581         int error;
 582         char kname[XATTR_NAME_MAX + 1];
 583
 584         error = strncpy_from_user(kname, name, sizeof(kname));
 585         if (error == 0 || error == sizeof(kname))
 586                 error = -ERANGE;
 587         if (error < 0)
 588                 return error;
 589
 590         return vfs_removexattr(d, kname);
 591 }
 592
 593 static int path_removexattr(const char __user *pathname,
 594                             const char __user *name, unsigned int lookup_flags)
 595 {
 596         struct path path;
 597         int error;
 598 retry:
 599         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 600         if (error)
 601                 return error;
 602         error = mnt_want_write(path.mnt);
 603         if (!error) {
 604                 error = removexattr(path.dentry, name);
 605                 mnt_drop_write(path.mnt);
 606         }
 607         path_put(&path);
 608         if (retry_estale(error, lookup_flags)) {
 609                 lookup_flags |= LOOKUP_REVAL;
 610                 goto retry;
 611         }
 612         return error;
 613 }
 614
 615 SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
 616                 const char __user *, name)
 617 {
 618         return path_removexattr(pathname, name, LOOKUP_FOLLOW);
 619 }
 620
 621 SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
 622                 const char __user *, name)
 623 {
 624         return path_removexattr(pathname, name, 0);
 625 }
 626
 627 SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
 628 {
 629         struct fd f = fdget(fd);
 630         int error = -EBADF;
 631
 632         if (!f.file)
 633                 return error;
 634         audit_file(f.file);
 635         error = mnt_want_write_file(f.file);
 636         if (!error) {
 637                 error = removexattr(f.file->f_path.dentry, name);
 638                 mnt_drop_write_file(f.file);
 639         }
 640         fdput(f);
 641         return error;
 642 }
 643
 644
 645 static const char *
 646 strcmp_prefix(const char *a, const char *a_prefix)
 647 {
 648         while (*a_prefix && *a == *a_prefix) {
 649                 a++;
 650                 a_prefix++;
 651         }
 652         return *a_prefix ? NULL : a;
 653 }
 654
 655 /*
 656  * In order to implement different sets of xattr operations for each xattr
 657  * prefix with the generic xattr API, a filesystem should create a
 658  * null-terminated array of struct xattr_handler (one for each prefix) and
 659  * hang a pointer to it off of the s_xattr field of the superblock.
 660  *
 661  * The generic_fooxattr() functions will use this list to dispatch xattr
 662  * operations to the correct xattr_handler.
 663  */
 664 #define for_each_xattr_handler(handlers, handler)               \
 665         if (handlers)                                           \
 666                 for ((handler) = *(handlers)++;                 \
 667                         (handler) != NULL;                      \
 668                         (handler) = *(handlers)++)
 669
 670 /*
 671  * Find the xattr_handler with the matching prefix.
 672  */
 673 static const struct xattr_handler *
 674 xattr_resolve_name(const struct xattr_handler **handlers, const char **name)
 675 {
 676         const struct xattr_handler *handler;
 677
 678         if (!*name)
 679                 return ERR_PTR(-EINVAL);
 680
 681         for_each_xattr_handler(handlers, handler) {
 682                 const char *n;
 683
 684                 n = strcmp_prefix(*name, xattr_prefix(handler));
 685                 if (n) {
 686                         if (!handler->prefix ^ !*n) {
 687                                 if (*n)
 688                                         continue;
 689                                 return ERR_PTR(-EINVAL);
 690                         }
 691                         *name = n;
 692                         return handler;
 693                 }
 694         }
 695         return ERR_PTR(-EOPNOTSUPP);
 696 }
 697
 698 /*
 699  * Find the handler for the prefix and dispatch its get() operation.
 700  */
 701 ssize_t
 702 generic_getxattr(struct dentry *dentry, struct inode *inode,
 703                  const char *name, void *buffer, size_t size)
 704 {
 705         const struct xattr_handler *handler;
 706
 707         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 708         if (IS_ERR(handler))
 709                 return PTR_ERR(handler);
 710         return handler->get(handler, dentry, inode,
 711                             name, buffer, size);
 712 }
 713
 714 /*
 715  * Combine the results of the list() operation from every xattr_handler in the
 716  * list.
 717  */
 718 ssize_t
 719 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 720 {
 721         const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
 722         unsigned int size = 0;
 723
 724         if (!buffer) {
 725                 for_each_xattr_handler(handlers, handler) {
 726                         if (!handler->name ||
 727                             (handler->list && !handler->list(dentry)))
 728                                 continue;
 729                         size += strlen(handler->name) + 1;
 730                 }
 731         } else {
 732                 char *buf = buffer;
 733                 size_t len;
 734
 735                 for_each_xattr_handler(handlers, handler) {
 736                         if (!handler->name ||
 737                             (handler->list && !handler->list(dentry)))
 738                                 continue;
 739                         len = strlen(handler->name);
 740                         if (len + 1 > buffer_size)
 741                                 return -ERANGE;
 742                         memcpy(buf, handler->name, len + 1);
 743                         buf += len + 1;
 744                         buffer_size -= len + 1;
 745                 }
 746                 size = buf - buffer;
 747         }
 748         return size;
 749 }
 750
 751 /*
 752  * Find the handler for the prefix and dispatch its set() operation.
 753  */
 754 int
 755 generic_setxattr(struct dentry *dentry, struct inode *inode, const char *name,
 756                  const void *value, size_t size, int flags)
 757 {
 758         const struct xattr_handler *handler;
 759
 760         if (size == 0)
 761                 value = "";  /* empty EA, do not remove */
 762         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 763         if (IS_ERR(handler))
 764                 return PTR_ERR(handler);
 765         return handler->set(handler, dentry, inode, name, value, size, flags);
 766 }
 767
 768 /*
 769  * Find the handler for the prefix and dispatch its set() operation to remove
 770  * any associated extended attribute.
 771  */
 772 int
 773 generic_removexattr(struct dentry *dentry, const char *name)
 774 {
 775         const struct xattr_handler *handler;
 776
 777         handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
 778         if (IS_ERR(handler))
 779                 return PTR_ERR(handler);
 780         return handler->set(handler, dentry, d_inode(dentry), name, NULL,
 781                             0, XATTR_REPLACE);
 782 }
 783
 784 EXPORT_SYMBOL(generic_getxattr);
 785 EXPORT_SYMBOL(generic_listxattr);
 786 EXPORT_SYMBOL(generic_setxattr);
 787 EXPORT_SYMBOL(generic_removexattr);
 788
 789 /**
 790  * xattr_full_name  -  Compute full attribute name from suffix
 791  *
 792  * @handler:    handler of the xattr_handler operation
 793  * @name:       name passed to the xattr_handler operation
 794  *
 795  * The get and set xattr handler operations are called with the remainder of
 796  * the attribute name after skipping the handler's prefix: for example, "foo"
 797  * is passed to the get operation of a handler with prefix "user." to get
 798  * attribute "user.foo".  The full name is still "there" in the name though.
 799  *
 800  * Note: the list xattr handler operation when called from the vfs is passed a
 801  * NULL name; some file systems use this operation internally, with varying
 802  * semantics.
 803  */
 804 const char *xattr_full_name(const struct xattr_handler *handler,
 805                             const char *name)
 806 {
 807         size_t prefix_len = strlen(xattr_prefix(handler));
 808
 809         return name - prefix_len;
 810 }
 811 EXPORT_SYMBOL(xattr_full_name);
 812
 813 /*
 814  * Allocate new xattr and copy in the value; but leave the name to callers.
 815  */
 816 struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
 817 {
 818         struct simple_xattr *new_xattr;
 819         size_t len;
 820
 821         /* wrap around? */
 822         len = sizeof(*new_xattr) + size;
 823         if (len < sizeof(*new_xattr))
 824                 return NULL;
 825
 826         new_xattr = kmalloc(len, GFP_KERNEL);
 827         if (!new_xattr)
 828                 return NULL;
 829
 830         new_xattr->size = size;
 831         memcpy(new_xattr->value, value, size);
 832         return new_xattr;
 833 }
 834
 835 /*
 836  * xattr GET operation for in-memory/pseudo filesystems
 837  */
 838 int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
 839                      void *buffer, size_t size)
 840 {
 841         struct simple_xattr *xattr;
 842         int ret = -ENODATA;
 843
 844         spin_lock(&xattrs->lock);
 845         list_for_each_entry(xattr, &xattrs->head, list) {
 846                 if (strcmp(name, xattr->name))
 847                         continue;
 848
 849                 ret = xattr->size;
 850                 if (buffer) {
 851                         if (size < xattr->size)
 852                                 ret = -ERANGE;
 853                         else
 854                                 memcpy(buffer, xattr->value, xattr->size);
 855                 }
 856                 break;
 857         }
 858         spin_unlock(&xattrs->lock);
 859         return ret;
 860 }
 861
 862 /**
 863  * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
 864  * @xattrs: target simple_xattr list
 865  * @name: name of the extended attribute
 866  * @value: value of the xattr. If %NULL, will remove the attribute.
 867  * @size: size of the new xattr
 868  * @flags: %XATTR_{CREATE|REPLACE}
 869  *
 870  * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
 871  * with -EEXIST.  If %XATTR_REPLACE is set, the xattr should exist;
 872  * otherwise, fails with -ENODATA.
 873  *
 874  * Returns 0 on success, -errno on failure.
 875  */
 876 int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
 877                      const void *value, size_t size, int flags)
 878 {
 879         struct simple_xattr *xattr;
 880         struct simple_xattr *new_xattr = NULL;
 881         int err = 0;
 882
 883         /* value == NULL means remove */
 884         if (value) {
 885                 new_xattr = simple_xattr_alloc(value, size);
 886                 if (!new_xattr)
 887                         return -ENOMEM;
 888
 889                 new_xattr->name = kstrdup(name, GFP_KERNEL);
 890                 if (!new_xattr->name) {
 891                         kfree(new_xattr);
 892                         return -ENOMEM;
 893                 }
 894         }
 895
 896         spin_lock(&xattrs->lock);
 897         list_for_each_entry(xattr, &xattrs->head, list) {
 898                 if (!strcmp(name, xattr->name)) {
 899                         if (flags & XATTR_CREATE) {
 900                                 xattr = new_xattr;
 901                                 err = -EEXIST;
 902                         } else if (new_xattr) {
 903                                 list_replace(&xattr->list, &new_xattr->list);
 904                         } else {
 905                                 list_del(&xattr->list);
 906                         }
 907                         goto out;
 908                 }
 909         }
 910         if (flags & XATTR_REPLACE) {
 911                 xattr = new_xattr;
 912                 err = -ENODATA;
 913         } else {
 914                 list_add(&new_xattr->list, &xattrs->head);
 915                 xattr = NULL;
 916         }
 917 out:
 918         spin_unlock(&xattrs->lock);
 919         if (xattr) {
 920                 kfree(xattr->name);
 921                 kfree(xattr);
 922         }
 923         return err;
 924
 925 }
 926
 927 static bool xattr_is_trusted(const char *name)
 928 {
 929         return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
 930 }
 931
 932 static int xattr_list_one(char **buffer, ssize_t *remaining_size,
 933                           const char *name)
 934 {
 935         size_t len = strlen(name) + 1;
 936         if (*buffer) {
 937                 if (*remaining_size < len)
 938                         return -ERANGE;
 939                 memcpy(*buffer, name, len);
 940                 *buffer += len;
 941         }
 942         *remaining_size -= len;
 943         return 0;
 944 }
 945
 946 /*
 947  * xattr LIST operation for in-memory/pseudo filesystems
 948  */
 949 ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs,
 950                           char *buffer, size_t size)
 951 {
 952         bool trusted = capable(CAP_SYS_ADMIN);
 953         struct simple_xattr *xattr;
 954         ssize_t remaining_size = size;
 955         int err = 0;
 956
 957 #ifdef CONFIG_FS_POSIX_ACL
 958         if (inode->i_acl) {
 959                 err = xattr_list_one(&buffer, &remaining_size,
 960                                      XATTR_NAME_POSIX_ACL_ACCESS);
 961                 if (err)
 962                         return err;
 963         }
 964         if (inode->i_default_acl) {
 965                 err = xattr_list_one(&buffer, &remaining_size,
 966                                      XATTR_NAME_POSIX_ACL_DEFAULT);
 967                 if (err)
 968                         return err;
 969         }
 970 #endif
 971
 972         spin_lock(&xattrs->lock);
 973         list_for_each_entry(xattr, &xattrs->head, list) {
 974                 /* skip "trusted." attributes for unprivileged callers */
 975                 if (!trusted && xattr_is_trusted(xattr->name))
 976                         continue;
 977
 978                 err = xattr_list_one(&buffer, &remaining_size, xattr->name);
 979                 if (err)
 980                         break;
 981         }
 982         spin_unlock(&xattrs->lock);
 983
 984         return err ? err : size - remaining_size;
 985 }
 986
 987 /*
 988  * Adds an extended attribute to the list
 989  */
 990 void simple_xattr_list_add(struct simple_xattrs *xattrs,
 991                            struct simple_xattr *new_xattr)
 992 {
 993         spin_lock(&xattrs->lock);
 994         list_add(&new_xattr->list, &xattrs->head);
 995         spin_unlock(&xattrs->lock);
 996 }