fs/xattr.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3   File: fs/xattr.c
   4
   5   Extended attribute handling.
   6
   7   Copyright (C) 2001 by Andreas Gruenbacher <a.gruenbacher@computer.org>
   8   Copyright (C) 2001 SGI - Silicon Graphics, Inc <linux-xfs@oss.sgi.com>
   9   Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
  10  */
  11 #include <linux/fs.h>
  12 #include <linux/slab.h>
  13 #include <linux/file.h>
  14 #include <linux/xattr.h>
  15 #include <linux/mount.h>
  16 #include <linux/namei.h>
  17 #include <linux/security.h>
  18 #include <linux/evm.h>
  19 #include <linux/syscalls.h>
  20 #include <linux/export.h>
  21 #include <linux/fsnotify.h>
  22 #include <linux/audit.h>
  23 #include <linux/vmalloc.h>
  24 #include <linux/posix_acl_xattr.h>
  25
  26 #include <linux/uaccess.h>
  27
  28 static const char *
  29 strcmp_prefix(const char *a, const char *a_prefix)
  30 {
  31         while (*a_prefix && *a == *a_prefix) {
  32                 a++;
  33                 a_prefix++;
  34         }
  35         return *a_prefix ? NULL : a;
  36 }
  37
  38 /*
  39  * In order to implement different sets of xattr operations for each xattr
  40  * prefix, a filesystem should create a null-terminated array of struct
  41  * xattr_handler (one for each prefix) and hang a pointer to it off of the
  42  * s_xattr field of the superblock.
  43  */
  44 #define for_each_xattr_handler(handlers, handler)               \
  45         if (handlers)                                           \
  46                 for ((handler) = *(handlers)++;                 \
  47                         (handler) != NULL;                      \
  48                         (handler) = *(handlers)++)
  49
  50 /*
  51  * Find the xattr_handler with the matching prefix.
  52  */
  53 static const struct xattr_handler *
  54 xattr_resolve_name(struct inode *inode, const char **name)
  55 {
  56         const struct xattr_handler **handlers = inode->i_sb->s_xattr;
  57         const struct xattr_handler *handler;
  58
  59         if (!(inode->i_opflags & IOP_XATTR)) {
  60                 if (unlikely(is_bad_inode(inode)))
  61                         return ERR_PTR(-EIO);
  62                 return ERR_PTR(-EOPNOTSUPP);
  63         }
  64         for_each_xattr_handler(handlers, handler) {
  65                 const char *n;
  66
  67                 n = strcmp_prefix(*name, xattr_prefix(handler));
  68                 if (n) {
  69                         if (!handler->prefix ^ !*n) {
  70                                 if (*n)
  71                                         continue;
  72                                 return ERR_PTR(-EINVAL);
  73                         }
  74                         *name = n;
  75                         return handler;
  76                 }
  77         }
  78         return ERR_PTR(-EOPNOTSUPP);
  79 }
  80
  81 /*
  82  * Check permissions for extended attribute access.  This is a bit complicated
  83  * because different namespaces have very different rules.
  84  */
  85 static int
  86 xattr_permission(struct inode *inode, const char *name, int mask)
  87 {
  88         /*
  89          * We can never set or remove an extended attribute on a read-only
  90          * filesystem  or on an immutable / append-only inode.
  91          */
  92         if (mask & MAY_WRITE) {
  93                 if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
  94                         return -EPERM;
  95                 /*
  96                  * Updating an xattr will likely cause i_uid and i_gid
  97                  * to be writen back improperly if their true value is
  98                  * unknown to the vfs.
  99                  */
 100                 if (HAS_UNMAPPED_ID(inode))
 101                         return -EPERM;
 102         }
 103
 104         /*
 105          * No restriction for security.* and system.* from the VFS.  Decision
 106          * on these is left to the underlying filesystem / security module.
 107          */
 108         if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||
 109             !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
 110                 return 0;
 111
 112         /*
 113          * The trusted.* namespace can only be accessed by privileged users.
 114          */
 115         if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
 116                 if (!capable(CAP_SYS_ADMIN))
 117                         return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
 118                 return 0;
 119         }
 120
 121         /*
 122          * In the user.* namespace, only regular files and directories can have
 123          * extended attributes. For sticky directories, only the owner and
 124          * privileged users can write attributes.
 125          */
 126         if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
 127                 if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
 128                         return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
 129                 if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&
 130                     (mask & MAY_WRITE) && !inode_owner_or_capable(inode))
 131                         return -EPERM;
 132         }
 133
 134         return inode_permission(inode, mask);
 135 }
 136
 137 int
 138 __vfs_setxattr(struct dentry *dentry, struct inode *inode, const char *name,
 139                const void *value, size_t size, int flags)
 140 {
 141         const struct xattr_handler *handler;
 142
 143         handler = xattr_resolve_name(inode, &name);
 144         if (IS_ERR(handler))
 145                 return PTR_ERR(handler);
 146         if (!handler->set)
 147                 return -EOPNOTSUPP;
 148         if (size == 0)
 149                 value = "";  /* empty EA, do not remove */
 150         return handler->set(handler, dentry, inode, name, value, size, flags);
 151 }
 152 EXPORT_SYMBOL(__vfs_setxattr);
 153
 154 /**
 155  *  __vfs_setxattr_noperm - perform setxattr operation without performing
 156  *  permission checks.
 157  *
 158  *  @dentry - object to perform setxattr on
 159  *  @name - xattr name to set
 160  *  @value - value to set @name to
 161  *  @size - size of @value
 162  *  @flags - flags to pass into filesystem operations
 163  *
 164  *  returns the result of the internal setxattr or setsecurity operations.
 165  *
 166  *  This function requires the caller to lock the inode's i_mutex before it
 167  *  is executed. It also assumes that the caller will make the appropriate
 168  *  permission checks.
 169  */
 170 int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
 171                 const void *value, size_t size, int flags)
 172 {
 173         struct inode *inode = dentry->d_inode;
 174         int error = -EAGAIN;
 175         int issec = !strncmp(name, XATTR_SECURITY_PREFIX,
 176                                    XATTR_SECURITY_PREFIX_LEN);
 177
 178         if (issec)
 179                 inode->i_flags &= ~S_NOSEC;
 180         if (inode->i_opflags & IOP_XATTR) {
 181                 error = __vfs_setxattr(dentry, inode, name, value, size, flags);
 182                 if (!error) {
 183                         fsnotify_xattr(dentry);
 184                         security_inode_post_setxattr(dentry, name, value,
 185                                                      size, flags);
 186                 }
 187         } else {
 188                 if (unlikely(is_bad_inode(inode)))
 189                         return -EIO;
 190         }
 191         if (error == -EAGAIN) {
 192                 error = -EOPNOTSUPP;
 193
 194                 if (issec) {
 195                         const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
 196
 197                         error = security_inode_setsecurity(inode, suffix, value,
 198                                                            size, flags);
 199                         if (!error)
 200                                 fsnotify_xattr(dentry);
 201                 }
 202         }
 203
 204         return error;
 205 }
 206
 207 /**
 208  * __vfs_setxattr_locked: set an extended attribute while holding the inode
 209  * lock
 210  *
 211  *  @dentry - object to perform setxattr on
 212  *  @name - xattr name to set
 213  *  @value - value to set @name to
 214  *  @size - size of @value
 215  *  @flags - flags to pass into filesystem operations
 216  *  @delegated_inode - on return, will contain an inode pointer that
 217  *  a delegation was broken on, NULL if none.
 218  */
 219 int
 220 __vfs_setxattr_locked(struct dentry *dentry, const char *name,
 221                 const void *value, size_t size, int flags,
 222                 struct inode **delegated_inode)
 223 {
 224         struct inode *inode = dentry->d_inode;
 225         int error;
 226
 227         error = xattr_permission(inode, name, MAY_WRITE);
 228         if (error)
 229                 return error;
 230
 231         error = security_inode_setxattr(dentry, name, value, size, flags);
 232         if (error)
 233                 goto out;
 234
 235         error = try_break_deleg(inode, delegated_inode);
 236         if (error)
 237                 goto out;
 238
 239         error = __vfs_setxattr_noperm(dentry, name, value, size, flags);
 240
 241 out:
 242         return error;
 243 }
 244 EXPORT_SYMBOL_GPL(__vfs_setxattr_locked);
 245
 246 int
 247 vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
 248                 size_t size, int flags)
 249 {
 250         struct inode *inode = dentry->d_inode;
 251         struct inode *delegated_inode = NULL;
 252         int error;
 253
 254 retry_deleg:
 255         inode_lock(inode);
 256         error = __vfs_setxattr_locked(dentry, name, value, size, flags,
 257             &delegated_inode);
 258         inode_unlock(inode);
 259
 260         if (delegated_inode) {
 261                 error = break_deleg_wait(&delegated_inode);
 262                 if (!error)
 263                         goto retry_deleg;
 264         }
 265         return error;
 266 }
 267 EXPORT_SYMBOL_GPL(vfs_setxattr);
 268
 269 static ssize_t
 270 xattr_getsecurity(struct inode *inode, const char *name, void *value,
 271                         size_t size)
 272 {
 273         void *buffer = NULL;
 274         ssize_t len;
 275
 276         if (!value || !size) {
 277                 len = security_inode_getsecurity(inode, name, &buffer, false);
 278                 goto out_noalloc;
 279         }
 280
 281         len = security_inode_getsecurity(inode, name, &buffer, true);
 282         if (len < 0)
 283                 return len;
 284         if (size < len) {
 285                 len = -ERANGE;
 286                 goto out;
 287         }
 288         memcpy(value, buffer, len);
 289 out:
 290         kfree(buffer);
 291 out_noalloc:
 292         return len;
 293 }
 294
 295 /*
 296  * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
 297  *
 298  * Allocate memory, if not already allocated, or re-allocate correct size,
 299  * before retrieving the extended attribute.
 300  *
 301  * Returns the result of alloc, if failed, or the getxattr operation.
 302  */
 303 ssize_t
 304 vfs_getxattr_alloc(struct dentry *dentry, const char *name, char **xattr_value,
 305                    size_t xattr_size, gfp_t flags)
 306 {
 307         const struct xattr_handler *handler;
 308         struct inode *inode = dentry->d_inode;
 309         char *value = *xattr_value;
 310         int error;
 311
 312         error = xattr_permission(inode, name, MAY_READ);
 313         if (error)
 314                 return error;
 315
 316         handler = xattr_resolve_name(inode, &name);
 317         if (IS_ERR(handler))
 318                 return PTR_ERR(handler);
 319         if (!handler->get)
 320                 return -EOPNOTSUPP;
 321         error = handler->get(handler, dentry, inode, name, NULL, 0);
 322         if (error < 0)
 323                 return error;
 324
 325         if (!value || (error > xattr_size)) {
 326                 value = krealloc(*xattr_value, error + 1, flags);
 327                 if (!value)
 328                         return -ENOMEM;
 329                 memset(value, 0, error + 1);
 330         }
 331
 332         error = handler->get(handler, dentry, inode, name, value, error);
 333         *xattr_value = value;
 334         return error;
 335 }
 336
 337 ssize_t
 338 __vfs_getxattr(struct dentry *dentry, struct inode *inode, const char *name,
 339                void *value, size_t size)
 340 {
 341         const struct xattr_handler *handler;
 342
 343         handler = xattr_resolve_name(inode, &name);
 344         if (IS_ERR(handler))
 345                 return PTR_ERR(handler);
 346         if (!handler->get)
 347                 return -EOPNOTSUPP;
 348         return handler->get(handler, dentry, inode, name, value, size);
 349 }
 350 EXPORT_SYMBOL(__vfs_getxattr);
 351
 352 ssize_t
 353 vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
 354 {
 355         struct inode *inode = dentry->d_inode;
 356         int error;
 357
 358         error = xattr_permission(inode, name, MAY_READ);
 359         if (error)
 360                 return error;
 361
 362         error = security_inode_getxattr(dentry, name);
 363         if (error)
 364                 return error;
 365
 366         if (!strncmp(name, XATTR_SECURITY_PREFIX,
 367                                 XATTR_SECURITY_PREFIX_LEN)) {
 368                 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
 369                 int ret = xattr_getsecurity(inode, suffix, value, size);
 370                 /*
 371                  * Only overwrite the return value if a security module
 372                  * is actually active.
 373                  */
 374                 if (ret == -EOPNOTSUPP)
 375                         goto nolsm;
 376                 return ret;
 377         }
 378 nolsm:
 379         return __vfs_getxattr(dentry, inode, name, value, size);
 380 }
 381 EXPORT_SYMBOL_GPL(vfs_getxattr);
 382
 383 ssize_t
 384 vfs_listxattr(struct dentry *dentry, char *list, size_t size)
 385 {
 386         struct inode *inode = d_inode(dentry);
 387         ssize_t error;
 388
 389         error = security_inode_listxattr(dentry);
 390         if (error)
 391                 return error;
 392         if (inode->i_op->listxattr && (inode->i_opflags & IOP_XATTR)) {
 393                 error = inode->i_op->listxattr(dentry, list, size);
 394         } else {
 395                 error = security_inode_listsecurity(inode, list, size);
 396                 if (size && error > size)
 397                         error = -ERANGE;
 398         }
 399         return error;
 400 }
 401 EXPORT_SYMBOL_GPL(vfs_listxattr);
 402
 403 int
 404 __vfs_removexattr(struct dentry *dentry, const char *name)
 405 {
 406         struct inode *inode = d_inode(dentry);
 407         const struct xattr_handler *handler;
 408
 409         handler = xattr_resolve_name(inode, &name);
 410         if (IS_ERR(handler))
 411                 return PTR_ERR(handler);
 412         if (!handler->set)
 413                 return -EOPNOTSUPP;
 414         return handler->set(handler, dentry, inode, name, NULL, 0, XATTR_REPLACE);
 415 }
 416 EXPORT_SYMBOL(__vfs_removexattr);
 417
 418 /**
 419  * __vfs_removexattr_locked: set an extended attribute while holding the inode
 420  * lock
 421  *
 422  *  @dentry - object to perform setxattr on
 423  *  @name - name of xattr to remove
 424  *  @delegated_inode - on return, will contain an inode pointer that
 425  *  a delegation was broken on, NULL if none.
 426  */
 427 int
 428 __vfs_removexattr_locked(struct dentry *dentry, const char *name,
 429                 struct inode **delegated_inode)
 430 {
 431         struct inode *inode = dentry->d_inode;
 432         int error;
 433
 434         error = xattr_permission(inode, name, MAY_WRITE);
 435         if (error)
 436                 return error;
 437
 438         error = security_inode_removexattr(dentry, name);
 439         if (error)
 440                 goto out;
 441
 442         error = try_break_deleg(inode, delegated_inode);
 443         if (error)
 444                 goto out;
 445
 446         error = __vfs_removexattr(dentry, name);
 447
 448         if (!error) {
 449                 fsnotify_xattr(dentry);
 450                 evm_inode_post_removexattr(dentry, name);
 451         }
 452
 453 out:
 454         return error;
 455 }
 456 EXPORT_SYMBOL_GPL(__vfs_removexattr_locked);
 457
 458 int
 459 vfs_removexattr(struct dentry *dentry, const char *name)
 460 {
 461         struct inode *inode = dentry->d_inode;
 462         struct inode *delegated_inode = NULL;
 463         int error;
 464
 465 retry_deleg:
 466         inode_lock(inode);
 467         error = __vfs_removexattr_locked(dentry, name, &delegated_inode);
 468         inode_unlock(inode);
 469
 470         if (delegated_inode) {
 471                 error = break_deleg_wait(&delegated_inode);
 472                 if (!error)
 473                         goto retry_deleg;
 474         }
 475
 476         return error;
 477 }
 478 EXPORT_SYMBOL_GPL(vfs_removexattr);
 479
 480 /*
 481  * Extended attribute SET operations
 482  */
 483 static long
 484 setxattr(struct dentry *d, const char __user *name, const void __user *value,
 485          size_t size, int flags)
 486 {
 487         int error;
 488         void *kvalue = NULL;
 489         char kname[XATTR_NAME_MAX + 1];
 490
 491         if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
 492                 return -EINVAL;
 493
 494         error = strncpy_from_user(kname, name, sizeof(kname));
 495         if (error == 0 || error == sizeof(kname))
 496                 error = -ERANGE;
 497         if (error < 0)
 498                 return error;
 499
 500         if (size) {
 501                 if (size > XATTR_SIZE_MAX)
 502                         return -E2BIG;
 503                 kvalue = kvmalloc(size, GFP_KERNEL);
 504                 if (!kvalue)
 505                         return -ENOMEM;
 506                 if (copy_from_user(kvalue, value, size)) {
 507                         error = -EFAULT;
 508                         goto out;
 509                 }
 510                 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
 511                     (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
 512                         posix_acl_fix_xattr_from_user(kvalue, size);
 513                 else if (strcmp(kname, XATTR_NAME_CAPS) == 0) {
 514                         error = cap_convert_nscap(d, &kvalue, size);
 515                         if (error < 0)
 516                                 goto out;
 517                         size = error;
 518                 }
 519         }
 520
 521         error = vfs_setxattr(d, kname, kvalue, size, flags);
 522 out:
 523         kvfree(kvalue);
 524
 525         return error;
 526 }
 527
 528 static int path_setxattr(const char __user *pathname,
 529                          const char __user *name, const void __user *value,
 530                          size_t size, int flags, unsigned int lookup_flags)
 531 {
 532         struct path path;
 533         int error;
 534 retry:
 535         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 536         if (error)
 537                 return error;
 538         error = mnt_want_write(path.mnt);
 539         if (!error) {
 540                 error = setxattr(path.dentry, name, value, size, flags);
 541                 mnt_drop_write(path.mnt);
 542         }
 543         path_put(&path);
 544         if (retry_estale(error, lookup_flags)) {
 545                 lookup_flags |= LOOKUP_REVAL;
 546                 goto retry;
 547         }
 548         return error;
 549 }
 550
 551 SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
 552                 const char __user *, name, const void __user *, value,
 553                 size_t, size, int, flags)
 554 {
 555         return path_setxattr(pathname, name, value, size, flags, LOOKUP_FOLLOW);
 556 }
 557
 558 SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
 559                 const char __user *, name, const void __user *, value,
 560                 size_t, size, int, flags)
 561 {
 562         return path_setxattr(pathname, name, value, size, flags, 0);
 563 }
 564
 565 SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
 566                 const void __user *,value, size_t, size, int, flags)
 567 {
 568         struct fd f = fdget(fd);
 569         int error = -EBADF;
 570
 571         if (!f.file)
 572                 return error;
 573         audit_file(f.file);
 574         error = mnt_want_write_file(f.file);
 575         if (!error) {
 576                 error = setxattr(f.file->f_path.dentry, name, value, size, flags);
 577                 mnt_drop_write_file(f.file);
 578         }
 579         fdput(f);
 580         return error;
 581 }
 582
 583 /*
 584  * Extended attribute GET operations
 585  */
 586 static ssize_t
 587 getxattr(struct dentry *d, const char __user *name, void __user *value,
 588          size_t size)
 589 {
 590         ssize_t error;
 591         void *kvalue = NULL;
 592         char kname[XATTR_NAME_MAX + 1];
 593
 594         error = strncpy_from_user(kname, name, sizeof(kname));
 595         if (error == 0 || error == sizeof(kname))
 596                 error = -ERANGE;
 597         if (error < 0)
 598                 return error;
 599
 600         if (size) {
 601                 if (size > XATTR_SIZE_MAX)
 602                         size = XATTR_SIZE_MAX;
 603                 kvalue = kvzalloc(size, GFP_KERNEL);
 604                 if (!kvalue)
 605                         return -ENOMEM;
 606         }
 607
 608         error = vfs_getxattr(d, kname, kvalue, size);
 609         if (error > 0) {
 610                 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
 611                     (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
 612                         posix_acl_fix_xattr_to_user(kvalue, error);
 613                 if (size && copy_to_user(value, kvalue, error))
 614                         error = -EFAULT;
 615         } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
 616                 /* The file system tried to returned a value bigger
 617                    than XATTR_SIZE_MAX bytes. Not possible. */
 618                 error = -E2BIG;
 619         }
 620
 621         kvfree(kvalue);
 622
 623         return error;
 624 }
 625
 626 static ssize_t path_getxattr(const char __user *pathname,
 627                              const char __user *name, void __user *value,
 628                              size_t size, unsigned int lookup_flags)
 629 {
 630         struct path path;
 631         ssize_t error;
 632 retry:
 633         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 634         if (error)
 635                 return error;
 636         error = getxattr(path.dentry, name, value, size);
 637         path_put(&path);
 638         if (retry_estale(error, lookup_flags)) {
 639                 lookup_flags |= LOOKUP_REVAL;
 640                 goto retry;
 641         }
 642         return error;
 643 }
 644
 645 SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
 646                 const char __user *, name, void __user *, value, size_t, size)
 647 {
 648         return path_getxattr(pathname, name, value, size, LOOKUP_FOLLOW);
 649 }
 650
 651 SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
 652                 const char __user *, name, void __user *, value, size_t, size)
 653 {
 654         return path_getxattr(pathname, name, value, size, 0);
 655 }
 656
 657 SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
 658                 void __user *, value, size_t, size)
 659 {
 660         struct fd f = fdget(fd);
 661         ssize_t error = -EBADF;
 662
 663         if (!f.file)
 664                 return error;
 665         audit_file(f.file);
 666         error = getxattr(f.file->f_path.dentry, name, value, size);
 667         fdput(f);
 668         return error;
 669 }
 670
 671 /*
 672  * Extended attribute LIST operations
 673  */
 674 static ssize_t
 675 listxattr(struct dentry *d, char __user *list, size_t size)
 676 {
 677         ssize_t error;
 678         char *klist = NULL;
 679
 680         if (size) {
 681                 if (size > XATTR_LIST_MAX)
 682                         size = XATTR_LIST_MAX;
 683                 klist = kvmalloc(size, GFP_KERNEL);
 684                 if (!klist)
 685                         return -ENOMEM;
 686         }
 687
 688         error = vfs_listxattr(d, klist, size);
 689         if (error > 0) {
 690                 if (size && copy_to_user(list, klist, error))
 691                         error = -EFAULT;
 692         } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
 693                 /* The file system tried to returned a list bigger
 694                    than XATTR_LIST_MAX bytes. Not possible. */
 695                 error = -E2BIG;
 696         }
 697
 698         kvfree(klist);
 699
 700         return error;
 701 }
 702
 703 static ssize_t path_listxattr(const char __user *pathname, char __user *list,
 704                               size_t size, unsigned int lookup_flags)
 705 {
 706         struct path path;
 707         ssize_t error;
 708 retry:
 709         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 710         if (error)
 711                 return error;
 712         error = listxattr(path.dentry, list, size);
 713         path_put(&path);
 714         if (retry_estale(error, lookup_flags)) {
 715                 lookup_flags |= LOOKUP_REVAL;
 716                 goto retry;
 717         }
 718         return error;
 719 }
 720
 721 SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
 722                 size_t, size)
 723 {
 724         return path_listxattr(pathname, list, size, LOOKUP_FOLLOW);
 725 }
 726
 727 SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
 728                 size_t, size)
 729 {
 730         return path_listxattr(pathname, list, size, 0);
 731 }
 732
 733 SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
 734 {
 735         struct fd f = fdget(fd);
 736         ssize_t error = -EBADF;
 737
 738         if (!f.file)
 739                 return error;
 740         audit_file(f.file);
 741         error = listxattr(f.file->f_path.dentry, list, size);
 742         fdput(f);
 743         return error;
 744 }
 745
 746 /*
 747  * Extended attribute REMOVE operations
 748  */
 749 static long
 750 removexattr(struct dentry *d, const char __user *name)
 751 {
 752         int error;
 753         char kname[XATTR_NAME_MAX + 1];
 754
 755         error = strncpy_from_user(kname, name, sizeof(kname));
 756         if (error == 0 || error == sizeof(kname))
 757                 error = -ERANGE;
 758         if (error < 0)
 759                 return error;
 760
 761         return vfs_removexattr(d, kname);
 762 }
 763
 764 static int path_removexattr(const char __user *pathname,
 765                             const char __user *name, unsigned int lookup_flags)
 766 {
 767         struct path path;
 768         int error;
 769 retry:
 770         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 771         if (error)
 772                 return error;
 773         error = mnt_want_write(path.mnt);
 774         if (!error) {
 775                 error = removexattr(path.dentry, name);
 776                 mnt_drop_write(path.mnt);
 777         }
 778         path_put(&path);
 779         if (retry_estale(error, lookup_flags)) {
 780                 lookup_flags |= LOOKUP_REVAL;
 781                 goto retry;
 782         }
 783         return error;
 784 }
 785
 786 SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
 787                 const char __user *, name)
 788 {
 789         return path_removexattr(pathname, name, LOOKUP_FOLLOW);
 790 }
 791
 792 SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
 793                 const char __user *, name)
 794 {
 795         return path_removexattr(pathname, name, 0);
 796 }
 797
 798 SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
 799 {
 800         struct fd f = fdget(fd);
 801         int error = -EBADF;
 802
 803         if (!f.file)
 804                 return error;
 805         audit_file(f.file);
 806         error = mnt_want_write_file(f.file);
 807         if (!error) {
 808                 error = removexattr(f.file->f_path.dentry, name);
 809                 mnt_drop_write_file(f.file);
 810         }
 811         fdput(f);
 812         return error;
 813 }
 814
 815 /*
 816  * Combine the results of the list() operation from every xattr_handler in the
 817  * list.
 818  */
 819 ssize_t
 820 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 821 {
 822         const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
 823         unsigned int size = 0;
 824
 825         if (!buffer) {
 826                 for_each_xattr_handler(handlers, handler) {
 827                         if (!handler->name ||
 828                             (handler->list && !handler->list(dentry)))
 829                                 continue;
 830                         size += strlen(handler->name) + 1;
 831                 }
 832         } else {
 833                 char *buf = buffer;
 834                 size_t len;
 835
 836                 for_each_xattr_handler(handlers, handler) {
 837                         if (!handler->name ||
 838                             (handler->list && !handler->list(dentry)))
 839                                 continue;
 840                         len = strlen(handler->name);
 841                         if (len + 1 > buffer_size)
 842                                 return -ERANGE;
 843                         memcpy(buf, handler->name, len + 1);
 844                         buf += len + 1;
 845                         buffer_size -= len + 1;
 846                 }
 847                 size = buf - buffer;
 848         }
 849         return size;
 850 }
 851 EXPORT_SYMBOL(generic_listxattr);
 852
 853 /**
 854  * xattr_full_name  -  Compute full attribute name from suffix
 855  *
 856  * @handler:    handler of the xattr_handler operation
 857  * @name:       name passed to the xattr_handler operation
 858  *
 859  * The get and set xattr handler operations are called with the remainder of
 860  * the attribute name after skipping the handler's prefix: for example, "foo"
 861  * is passed to the get operation of a handler with prefix "user." to get
 862  * attribute "user.foo".  The full name is still "there" in the name though.
 863  *
 864  * Note: the list xattr handler operation when called from the vfs is passed a
 865  * NULL name; some file systems use this operation internally, with varying
 866  * semantics.
 867  */
 868 const char *xattr_full_name(const struct xattr_handler *handler,
 869                             const char *name)
 870 {
 871         size_t prefix_len = strlen(xattr_prefix(handler));
 872
 873         return name - prefix_len;
 874 }
 875 EXPORT_SYMBOL(xattr_full_name);
 876
 877 /*
 878  * Allocate new xattr and copy in the value; but leave the name to callers.
 879  */
 880 struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
 881 {
 882         struct simple_xattr *new_xattr;
 883         size_t len;
 884
 885         /* wrap around? */
 886         len = sizeof(*new_xattr) + size;
 887         if (len < sizeof(*new_xattr))
 888                 return NULL;
 889
 890         new_xattr = kmalloc(len, GFP_KERNEL);
 891         if (!new_xattr)
 892                 return NULL;
 893
 894         new_xattr->size = size;
 895         memcpy(new_xattr->value, value, size);
 896         return new_xattr;
 897 }
 898
 899 /*
 900  * xattr GET operation for in-memory/pseudo filesystems
 901  */
 902 int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
 903                      void *buffer, size_t size)
 904 {
 905         struct simple_xattr *xattr;
 906         int ret = -ENODATA;
 907
 908         spin_lock(&xattrs->lock);
 909         list_for_each_entry(xattr, &xattrs->head, list) {
 910                 if (strcmp(name, xattr->name))
 911                         continue;
 912
 913                 ret = xattr->size;
 914                 if (buffer) {
 915                         if (size < xattr->size)
 916                                 ret = -ERANGE;
 917                         else
 918                                 memcpy(buffer, xattr->value, xattr->size);
 919                 }
 920                 break;
 921         }
 922         spin_unlock(&xattrs->lock);
 923         return ret;
 924 }
 925
 926 /**
 927  * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
 928  * @xattrs: target simple_xattr list
 929  * @name: name of the extended attribute
 930  * @value: value of the xattr. If %NULL, will remove the attribute.
 931  * @size: size of the new xattr
 932  * @flags: %XATTR_{CREATE|REPLACE}
 933  *
 934  * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
 935  * with -EEXIST.  If %XATTR_REPLACE is set, the xattr should exist;
 936  * otherwise, fails with -ENODATA.
 937  *
 938  * Returns 0 on success, -errno on failure.
 939  */
 940 int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
 941                      const void *value, size_t size, int flags)
 942 {
 943         struct simple_xattr *xattr;
 944         struct simple_xattr *new_xattr = NULL;
 945         int err = 0;
 946
 947         /* value == NULL means remove */
 948         if (value) {
 949                 new_xattr = simple_xattr_alloc(value, size);
 950                 if (!new_xattr)
 951                         return -ENOMEM;
 952
 953                 new_xattr->name = kstrdup(name, GFP_KERNEL);
 954                 if (!new_xattr->name) {
 955                         kfree(new_xattr);
 956                         return -ENOMEM;
 957                 }
 958         }
 959
 960         spin_lock(&xattrs->lock);
 961         list_for_each_entry(xattr, &xattrs->head, list) {
 962                 if (!strcmp(name, xattr->name)) {
 963                         if (flags & XATTR_CREATE) {
 964                                 xattr = new_xattr;
 965                                 err = -EEXIST;
 966                         } else if (new_xattr) {
 967                                 list_replace(&xattr->list, &new_xattr->list);
 968                         } else {
 969                                 list_del(&xattr->list);
 970                         }
 971                         goto out;
 972                 }
 973         }
 974         if (flags & XATTR_REPLACE) {
 975                 xattr = new_xattr;
 976                 err = -ENODATA;
 977         } else {
 978                 list_add(&new_xattr->list, &xattrs->head);
 979                 xattr = NULL;
 980         }
 981 out:
 982         spin_unlock(&xattrs->lock);
 983         if (xattr) {
 984                 kfree(xattr->name);
 985                 kfree(xattr);
 986         }
 987         return err;
 988
 989 }
 990
 991 static bool xattr_is_trusted(const char *name)
 992 {
 993         return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
 994 }
 995
 996 static int xattr_list_one(char **buffer, ssize_t *remaining_size,
 997                           const char *name)
 998 {
 999         size_t len = strlen(name) + 1;
1000         if (*buffer) {
1001                 if (*remaining_size < len)
1002                         return -ERANGE;
1003                 memcpy(*buffer, name, len);
1004                 *buffer += len;
1005         }
1006         *remaining_size -= len;
1007         return 0;
1008 }
1009
1010 /*
1011  * xattr LIST operation for in-memory/pseudo filesystems
1012  */
1013 ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs,
1014                           char *buffer, size_t size)
1015 {
1016         bool trusted = capable(CAP_SYS_ADMIN);
1017         struct simple_xattr *xattr;
1018         ssize_t remaining_size = size;
1019         int err = 0;
1020
1021 #ifdef CONFIG_FS_POSIX_ACL
1022         if (IS_POSIXACL(inode)) {
1023                 if (inode->i_acl) {
1024                         err = xattr_list_one(&buffer, &remaining_size,
1025                                              XATTR_NAME_POSIX_ACL_ACCESS);
1026                         if (err)
1027                                 return err;
1028                 }
1029                 if (inode->i_default_acl) {
1030                         err = xattr_list_one(&buffer, &remaining_size,
1031                                              XATTR_NAME_POSIX_ACL_DEFAULT);
1032                         if (err)
1033                                 return err;
1034                 }
1035         }
1036 #endif
1037
1038         spin_lock(&xattrs->lock);
1039         list_for_each_entry(xattr, &xattrs->head, list) {
1040                 /* skip "trusted." attributes for unprivileged callers */
1041                 if (!trusted && xattr_is_trusted(xattr->name))
1042                         continue;
1043
1044                 err = xattr_list_one(&buffer, &remaining_size, xattr->name);
1045                 if (err)
1046                         break;
1047         }
1048         spin_unlock(&xattrs->lock);
1049
1050         return err ? err : size - remaining_size;
1051 }
1052
1053 /*
1054  * Adds an extended attribute to the list
1055  */
1056 void simple_xattr_list_add(struct simple_xattrs *xattrs,
1057                            struct simple_xattr *new_xattr)
1058 {
1059         spin_lock(&xattrs->lock);
1060         list_add(&new_xattr->list, &xattrs->head);
1061         spin_unlock(&xattrs->lock);
1062 }