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 /*
 138  * Look for any handler that deals with the specified namespace.
 139  */
 140 int
 141 xattr_supported_namespace(struct inode *inode, const char *prefix)
 142 {
 143         const struct xattr_handler **handlers = inode->i_sb->s_xattr;
 144         const struct xattr_handler *handler;
 145         size_t preflen;
 146
 147         if (!(inode->i_opflags & IOP_XATTR)) {
 148                 if (unlikely(is_bad_inode(inode)))
 149                         return -EIO;
 150                 return -EOPNOTSUPP;
 151         }
 152
 153         preflen = strlen(prefix);
 154
 155         for_each_xattr_handler(handlers, handler) {
 156                 if (!strncmp(xattr_prefix(handler), prefix, preflen))
 157                         return 0;
 158         }
 159
 160         return -EOPNOTSUPP;
 161 }
 162 EXPORT_SYMBOL(xattr_supported_namespace);
 163
 164 int
 165 __vfs_setxattr(struct dentry *dentry, struct inode *inode, const char *name,
 166                const void *value, size_t size, int flags)
 167 {
 168         const struct xattr_handler *handler;
 169
 170         handler = xattr_resolve_name(inode, &name);
 171         if (IS_ERR(handler))
 172                 return PTR_ERR(handler);
 173         if (!handler->set)
 174                 return -EOPNOTSUPP;
 175         if (size == 0)
 176                 value = "";  /* empty EA, do not remove */
 177         return handler->set(handler, dentry, inode, name, value, size, flags);
 178 }
 179 EXPORT_SYMBOL(__vfs_setxattr);
 180
 181 /**
 182  *  __vfs_setxattr_noperm - perform setxattr operation without performing
 183  *  permission checks.
 184  *
 185  *  @dentry - object to perform setxattr on
 186  *  @name - xattr name to set
 187  *  @value - value to set @name to
 188  *  @size - size of @value
 189  *  @flags - flags to pass into filesystem operations
 190  *
 191  *  returns the result of the internal setxattr or setsecurity operations.
 192  *
 193  *  This function requires the caller to lock the inode's i_mutex before it
 194  *  is executed. It also assumes that the caller will make the appropriate
 195  *  permission checks.
 196  */
 197 int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
 198                 const void *value, size_t size, int flags)
 199 {
 200         struct inode *inode = dentry->d_inode;
 201         int error = -EAGAIN;
 202         int issec = !strncmp(name, XATTR_SECURITY_PREFIX,
 203                                    XATTR_SECURITY_PREFIX_LEN);
 204
 205         if (issec)
 206                 inode->i_flags &= ~S_NOSEC;
 207         if (inode->i_opflags & IOP_XATTR) {
 208                 error = __vfs_setxattr(dentry, inode, name, value, size, flags);
 209                 if (!error) {
 210                         fsnotify_xattr(dentry);
 211                         security_inode_post_setxattr(dentry, name, value,
 212                                                      size, flags);
 213                 }
 214         } else {
 215                 if (unlikely(is_bad_inode(inode)))
 216                         return -EIO;
 217         }
 218         if (error == -EAGAIN) {
 219                 error = -EOPNOTSUPP;
 220
 221                 if (issec) {
 222                         const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
 223
 224                         error = security_inode_setsecurity(inode, suffix, value,
 225                                                            size, flags);
 226                         if (!error)
 227                                 fsnotify_xattr(dentry);
 228                 }
 229         }
 230
 231         return error;
 232 }
 233
 234 /**
 235  * __vfs_setxattr_locked - set an extended attribute while holding the inode
 236  * lock
 237  *
 238  *  @dentry: object to perform setxattr on
 239  *  @name: xattr name to set
 240  *  @value: value to set @name to
 241  *  @size: size of @value
 242  *  @flags: flags to pass into filesystem operations
 243  *  @delegated_inode: on return, will contain an inode pointer that
 244  *  a delegation was broken on, NULL if none.
 245  */
 246 int
 247 __vfs_setxattr_locked(struct dentry *dentry, const char *name,
 248                 const void *value, size_t size, int flags,
 249                 struct inode **delegated_inode)
 250 {
 251         struct inode *inode = dentry->d_inode;
 252         int error;
 253
 254         error = xattr_permission(inode, name, MAY_WRITE);
 255         if (error)
 256                 return error;
 257
 258         error = security_inode_setxattr(dentry, name, value, size, flags);
 259         if (error)
 260                 goto out;
 261
 262         error = try_break_deleg(inode, delegated_inode);
 263         if (error)
 264                 goto out;
 265
 266         error = __vfs_setxattr_noperm(dentry, name, value, size, flags);
 267
 268 out:
 269         return error;
 270 }
 271 EXPORT_SYMBOL_GPL(__vfs_setxattr_locked);
 272
 273 int
 274 vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
 275                 size_t size, int flags)
 276 {
 277         struct inode *inode = dentry->d_inode;
 278         struct inode *delegated_inode = NULL;
 279         int error;
 280
 281 retry_deleg:
 282         inode_lock(inode);
 283         error = __vfs_setxattr_locked(dentry, name, value, size, flags,
 284             &delegated_inode);
 285         inode_unlock(inode);
 286
 287         if (delegated_inode) {
 288                 error = break_deleg_wait(&delegated_inode);
 289                 if (!error)
 290                         goto retry_deleg;
 291         }
 292         return error;
 293 }
 294 EXPORT_SYMBOL_GPL(vfs_setxattr);
 295
 296 static ssize_t
 297 xattr_getsecurity(struct inode *inode, const char *name, void *value,
 298                         size_t size)
 299 {
 300         void *buffer = NULL;
 301         ssize_t len;
 302
 303         if (!value || !size) {
 304                 len = security_inode_getsecurity(inode, name, &buffer, false);
 305                 goto out_noalloc;
 306         }
 307
 308         len = security_inode_getsecurity(inode, name, &buffer, true);
 309         if (len < 0)
 310                 return len;
 311         if (size < len) {
 312                 len = -ERANGE;
 313                 goto out;
 314         }
 315         memcpy(value, buffer, len);
 316 out:
 317         kfree(buffer);
 318 out_noalloc:
 319         return len;
 320 }
 321
 322 /*
 323  * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
 324  *
 325  * Allocate memory, if not already allocated, or re-allocate correct size,
 326  * before retrieving the extended attribute.
 327  *
 328  * Returns the result of alloc, if failed, or the getxattr operation.
 329  */
 330 ssize_t
 331 vfs_getxattr_alloc(struct dentry *dentry, const char *name, char **xattr_value,
 332                    size_t xattr_size, gfp_t flags)
 333 {
 334         const struct xattr_handler *handler;
 335         struct inode *inode = dentry->d_inode;
 336         char *value = *xattr_value;
 337         int error;
 338
 339         error = xattr_permission(inode, name, MAY_READ);
 340         if (error)
 341                 return error;
 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         error = handler->get(handler, dentry, inode, name, NULL, 0);
 349         if (error < 0)
 350                 return error;
 351
 352         if (!value || (error > xattr_size)) {
 353                 value = krealloc(*xattr_value, error + 1, flags);
 354                 if (!value)
 355                         return -ENOMEM;
 356                 memset(value, 0, error + 1);
 357         }
 358
 359         error = handler->get(handler, dentry, inode, name, value, error);
 360         *xattr_value = value;
 361         return error;
 362 }
 363
 364 ssize_t
 365 __vfs_getxattr(struct dentry *dentry, struct inode *inode, const char *name,
 366                void *value, size_t size)
 367 {
 368         const struct xattr_handler *handler;
 369
 370         handler = xattr_resolve_name(inode, &name);
 371         if (IS_ERR(handler))
 372                 return PTR_ERR(handler);
 373         if (!handler->get)
 374                 return -EOPNOTSUPP;
 375         return handler->get(handler, dentry, inode, name, value, size);
 376 }
 377 EXPORT_SYMBOL(__vfs_getxattr);
 378
 379 ssize_t
 380 vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
 381 {
 382         struct inode *inode = dentry->d_inode;
 383         int error;
 384
 385         error = xattr_permission(inode, name, MAY_READ);
 386         if (error)
 387                 return error;
 388
 389         error = security_inode_getxattr(dentry, name);
 390         if (error)
 391                 return error;
 392
 393         if (!strncmp(name, XATTR_SECURITY_PREFIX,
 394                                 XATTR_SECURITY_PREFIX_LEN)) {
 395                 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
 396                 int ret = xattr_getsecurity(inode, suffix, value, size);
 397                 /*
 398                  * Only overwrite the return value if a security module
 399                  * is actually active.
 400                  */
 401                 if (ret == -EOPNOTSUPP)
 402                         goto nolsm;
 403                 return ret;
 404         }
 405 nolsm:
 406         return __vfs_getxattr(dentry, inode, name, value, size);
 407 }
 408 EXPORT_SYMBOL_GPL(vfs_getxattr);
 409
 410 ssize_t
 411 vfs_listxattr(struct dentry *dentry, char *list, size_t size)
 412 {
 413         struct inode *inode = d_inode(dentry);
 414         ssize_t error;
 415
 416         error = security_inode_listxattr(dentry);
 417         if (error)
 418                 return error;
 419         if (inode->i_op->listxattr && (inode->i_opflags & IOP_XATTR)) {
 420                 error = inode->i_op->listxattr(dentry, list, size);
 421         } else {
 422                 error = security_inode_listsecurity(inode, list, size);
 423                 if (size && error > size)
 424                         error = -ERANGE;
 425         }
 426         return error;
 427 }
 428 EXPORT_SYMBOL_GPL(vfs_listxattr);
 429
 430 int
 431 __vfs_removexattr(struct dentry *dentry, const char *name)
 432 {
 433         struct inode *inode = d_inode(dentry);
 434         const struct xattr_handler *handler;
 435
 436         handler = xattr_resolve_name(inode, &name);
 437         if (IS_ERR(handler))
 438                 return PTR_ERR(handler);
 439         if (!handler->set)
 440                 return -EOPNOTSUPP;
 441         return handler->set(handler, dentry, inode, name, NULL, 0, XATTR_REPLACE);
 442 }
 443 EXPORT_SYMBOL(__vfs_removexattr);
 444
 445 /**
 446  * __vfs_removexattr_locked - set an extended attribute while holding the inode
 447  * lock
 448  *
 449  *  @dentry: object to perform setxattr on
 450  *  @name: name of xattr to remove
 451  *  @delegated_inode: on return, will contain an inode pointer that
 452  *  a delegation was broken on, NULL if none.
 453  */
 454 int
 455 __vfs_removexattr_locked(struct dentry *dentry, const char *name,
 456                 struct inode **delegated_inode)
 457 {
 458         struct inode *inode = dentry->d_inode;
 459         int error;
 460
 461         error = xattr_permission(inode, name, MAY_WRITE);
 462         if (error)
 463                 return error;
 464
 465         error = security_inode_removexattr(dentry, name);
 466         if (error)
 467                 goto out;
 468
 469         error = try_break_deleg(inode, delegated_inode);
 470         if (error)
 471                 goto out;
 472
 473         error = __vfs_removexattr(dentry, name);
 474
 475         if (!error) {
 476                 fsnotify_xattr(dentry);
 477                 evm_inode_post_removexattr(dentry, name);
 478         }
 479
 480 out:
 481         return error;
 482 }
 483 EXPORT_SYMBOL_GPL(__vfs_removexattr_locked);
 484
 485 int
 486 vfs_removexattr(struct dentry *dentry, const char *name)
 487 {
 488         struct inode *inode = dentry->d_inode;
 489         struct inode *delegated_inode = NULL;
 490         int error;
 491
 492 retry_deleg:
 493         inode_lock(inode);
 494         error = __vfs_removexattr_locked(dentry, name, &delegated_inode);
 495         inode_unlock(inode);
 496
 497         if (delegated_inode) {
 498                 error = break_deleg_wait(&delegated_inode);
 499                 if (!error)
 500                         goto retry_deleg;
 501         }
 502
 503         return error;
 504 }
 505 EXPORT_SYMBOL_GPL(vfs_removexattr);
 506
 507 /*
 508  * Extended attribute SET operations
 509  */
 510 static long
 511 setxattr(struct dentry *d, const char __user *name, const void __user *value,
 512          size_t size, int flags)
 513 {
 514         int error;
 515         void *kvalue = NULL;
 516         char kname[XATTR_NAME_MAX + 1];
 517
 518         if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
 519                 return -EINVAL;
 520
 521         error = strncpy_from_user(kname, name, sizeof(kname));
 522         if (error == 0 || error == sizeof(kname))
 523                 error = -ERANGE;
 524         if (error < 0)
 525                 return error;
 526
 527         if (size) {
 528                 if (size > XATTR_SIZE_MAX)
 529                         return -E2BIG;
 530                 kvalue = kvmalloc(size, GFP_KERNEL);
 531                 if (!kvalue)
 532                         return -ENOMEM;
 533                 if (copy_from_user(kvalue, value, size)) {
 534                         error = -EFAULT;
 535                         goto out;
 536                 }
 537                 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
 538                     (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
 539                         posix_acl_fix_xattr_from_user(kvalue, size);
 540                 else if (strcmp(kname, XATTR_NAME_CAPS) == 0) {
 541                         error = cap_convert_nscap(d, &kvalue, size);
 542                         if (error < 0)
 543                                 goto out;
 544                         size = error;
 545                 }
 546         }
 547
 548         error = vfs_setxattr(d, kname, kvalue, size, flags);
 549 out:
 550         kvfree(kvalue);
 551
 552         return error;
 553 }
 554
 555 static int path_setxattr(const char __user *pathname,
 556                          const char __user *name, const void __user *value,
 557                          size_t size, int flags, unsigned int lookup_flags)
 558 {
 559         struct path path;
 560         int error;
 561 retry:
 562         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 563         if (error)
 564                 return error;
 565         error = mnt_want_write(path.mnt);
 566         if (!error) {
 567                 error = setxattr(path.dentry, name, value, size, flags);
 568                 mnt_drop_write(path.mnt);
 569         }
 570         path_put(&path);
 571         if (retry_estale(error, lookup_flags)) {
 572                 lookup_flags |= LOOKUP_REVAL;
 573                 goto retry;
 574         }
 575         return error;
 576 }
 577
 578 SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
 579                 const char __user *, name, const void __user *, value,
 580                 size_t, size, int, flags)
 581 {
 582         return path_setxattr(pathname, name, value, size, flags, LOOKUP_FOLLOW);
 583 }
 584
 585 SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
 586                 const char __user *, name, const void __user *, value,
 587                 size_t, size, int, flags)
 588 {
 589         return path_setxattr(pathname, name, value, size, flags, 0);
 590 }
 591
 592 SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
 593                 const void __user *,value, size_t, size, int, flags)
 594 {
 595         struct fd f = fdget(fd);
 596         int error = -EBADF;
 597
 598         if (!f.file)
 599                 return error;
 600         audit_file(f.file);
 601         error = mnt_want_write_file(f.file);
 602         if (!error) {
 603                 error = setxattr(f.file->f_path.dentry, name, value, size, flags);
 604                 mnt_drop_write_file(f.file);
 605         }
 606         fdput(f);
 607         return error;
 608 }
 609
 610 /*
 611  * Extended attribute GET operations
 612  */
 613 static ssize_t
 614 getxattr(struct dentry *d, const char __user *name, void __user *value,
 615          size_t size)
 616 {
 617         ssize_t error;
 618         void *kvalue = NULL;
 619         char kname[XATTR_NAME_MAX + 1];
 620
 621         error = strncpy_from_user(kname, name, sizeof(kname));
 622         if (error == 0 || error == sizeof(kname))
 623                 error = -ERANGE;
 624         if (error < 0)
 625                 return error;
 626
 627         if (size) {
 628                 if (size > XATTR_SIZE_MAX)
 629                         size = XATTR_SIZE_MAX;
 630                 kvalue = kvzalloc(size, GFP_KERNEL);
 631                 if (!kvalue)
 632                         return -ENOMEM;
 633         }
 634
 635         error = vfs_getxattr(d, kname, kvalue, size);
 636         if (error > 0) {
 637                 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
 638                     (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
 639                         posix_acl_fix_xattr_to_user(kvalue, error);
 640                 if (size && copy_to_user(value, kvalue, error))
 641                         error = -EFAULT;
 642         } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
 643                 /* The file system tried to returned a value bigger
 644                    than XATTR_SIZE_MAX bytes. Not possible. */
 645                 error = -E2BIG;
 646         }
 647
 648         kvfree(kvalue);
 649
 650         return error;
 651 }
 652
 653 static ssize_t path_getxattr(const char __user *pathname,
 654                              const char __user *name, void __user *value,
 655                              size_t size, unsigned int lookup_flags)
 656 {
 657         struct path path;
 658         ssize_t error;
 659 retry:
 660         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 661         if (error)
 662                 return error;
 663         error = getxattr(path.dentry, name, value, size);
 664         path_put(&path);
 665         if (retry_estale(error, lookup_flags)) {
 666                 lookup_flags |= LOOKUP_REVAL;
 667                 goto retry;
 668         }
 669         return error;
 670 }
 671
 672 SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
 673                 const char __user *, name, void __user *, value, size_t, size)
 674 {
 675         return path_getxattr(pathname, name, value, size, LOOKUP_FOLLOW);
 676 }
 677
 678 SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
 679                 const char __user *, name, void __user *, value, size_t, size)
 680 {
 681         return path_getxattr(pathname, name, value, size, 0);
 682 }
 683
 684 SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
 685                 void __user *, value, size_t, size)
 686 {
 687         struct fd f = fdget(fd);
 688         ssize_t error = -EBADF;
 689
 690         if (!f.file)
 691                 return error;
 692         audit_file(f.file);
 693         error = getxattr(f.file->f_path.dentry, name, value, size);
 694         fdput(f);
 695         return error;
 696 }
 697
 698 /*
 699  * Extended attribute LIST operations
 700  */
 701 static ssize_t
 702 listxattr(struct dentry *d, char __user *list, size_t size)
 703 {
 704         ssize_t error;
 705         char *klist = NULL;
 706
 707         if (size) {
 708                 if (size > XATTR_LIST_MAX)
 709                         size = XATTR_LIST_MAX;
 710                 klist = kvmalloc(size, GFP_KERNEL);
 711                 if (!klist)
 712                         return -ENOMEM;
 713         }
 714
 715         error = vfs_listxattr(d, klist, size);
 716         if (error > 0) {
 717                 if (size && copy_to_user(list, klist, error))
 718                         error = -EFAULT;
 719         } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
 720                 /* The file system tried to returned a list bigger
 721                    than XATTR_LIST_MAX bytes. Not possible. */
 722                 error = -E2BIG;
 723         }
 724
 725         kvfree(klist);
 726
 727         return error;
 728 }
 729
 730 static ssize_t path_listxattr(const char __user *pathname, char __user *list,
 731                               size_t size, unsigned int lookup_flags)
 732 {
 733         struct path path;
 734         ssize_t error;
 735 retry:
 736         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 737         if (error)
 738                 return error;
 739         error = listxattr(path.dentry, list, size);
 740         path_put(&path);
 741         if (retry_estale(error, lookup_flags)) {
 742                 lookup_flags |= LOOKUP_REVAL;
 743                 goto retry;
 744         }
 745         return error;
 746 }
 747
 748 SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
 749                 size_t, size)
 750 {
 751         return path_listxattr(pathname, list, size, LOOKUP_FOLLOW);
 752 }
 753
 754 SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
 755                 size_t, size)
 756 {
 757         return path_listxattr(pathname, list, size, 0);
 758 }
 759
 760 SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
 761 {
 762         struct fd f = fdget(fd);
 763         ssize_t error = -EBADF;
 764
 765         if (!f.file)
 766                 return error;
 767         audit_file(f.file);
 768         error = listxattr(f.file->f_path.dentry, list, size);
 769         fdput(f);
 770         return error;
 771 }
 772
 773 /*
 774  * Extended attribute REMOVE operations
 775  */
 776 static long
 777 removexattr(struct dentry *d, const char __user *name)
 778 {
 779         int error;
 780         char kname[XATTR_NAME_MAX + 1];
 781
 782         error = strncpy_from_user(kname, name, sizeof(kname));
 783         if (error == 0 || error == sizeof(kname))
 784                 error = -ERANGE;
 785         if (error < 0)
 786                 return error;
 787
 788         return vfs_removexattr(d, kname);
 789 }
 790
 791 static int path_removexattr(const char __user *pathname,
 792                             const char __user *name, unsigned int lookup_flags)
 793 {
 794         struct path path;
 795         int error;
 796 retry:
 797         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 798         if (error)
 799                 return error;
 800         error = mnt_want_write(path.mnt);
 801         if (!error) {
 802                 error = removexattr(path.dentry, name);
 803                 mnt_drop_write(path.mnt);
 804         }
 805         path_put(&path);
 806         if (retry_estale(error, lookup_flags)) {
 807                 lookup_flags |= LOOKUP_REVAL;
 808                 goto retry;
 809         }
 810         return error;
 811 }
 812
 813 SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
 814                 const char __user *, name)
 815 {
 816         return path_removexattr(pathname, name, LOOKUP_FOLLOW);
 817 }
 818
 819 SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
 820                 const char __user *, name)
 821 {
 822         return path_removexattr(pathname, name, 0);
 823 }
 824
 825 SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
 826 {
 827         struct fd f = fdget(fd);
 828         int error = -EBADF;
 829
 830         if (!f.file)
 831                 return error;
 832         audit_file(f.file);
 833         error = mnt_want_write_file(f.file);
 834         if (!error) {
 835                 error = removexattr(f.file->f_path.dentry, name);
 836                 mnt_drop_write_file(f.file);
 837         }
 838         fdput(f);
 839         return error;
 840 }
 841
 842 /*
 843  * Combine the results of the list() operation from every xattr_handler in the
 844  * list.
 845  */
 846 ssize_t
 847 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 848 {
 849         const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
 850         unsigned int size = 0;
 851
 852         if (!buffer) {
 853                 for_each_xattr_handler(handlers, handler) {
 854                         if (!handler->name ||
 855                             (handler->list && !handler->list(dentry)))
 856                                 continue;
 857                         size += strlen(handler->name) + 1;
 858                 }
 859         } else {
 860                 char *buf = buffer;
 861                 size_t len;
 862
 863                 for_each_xattr_handler(handlers, handler) {
 864                         if (!handler->name ||
 865                             (handler->list && !handler->list(dentry)))
 866                                 continue;
 867                         len = strlen(handler->name);
 868                         if (len + 1 > buffer_size)
 869                                 return -ERANGE;
 870                         memcpy(buf, handler->name, len + 1);
 871                         buf += len + 1;
 872                         buffer_size -= len + 1;
 873                 }
 874                 size = buf - buffer;
 875         }
 876         return size;
 877 }
 878 EXPORT_SYMBOL(generic_listxattr);
 879
 880 /**
 881  * xattr_full_name  -  Compute full attribute name from suffix
 882  *
 883  * @handler:    handler of the xattr_handler operation
 884  * @name:       name passed to the xattr_handler operation
 885  *
 886  * The get and set xattr handler operations are called with the remainder of
 887  * the attribute name after skipping the handler's prefix: for example, "foo"
 888  * is passed to the get operation of a handler with prefix "user." to get
 889  * attribute "user.foo".  The full name is still "there" in the name though.
 890  *
 891  * Note: the list xattr handler operation when called from the vfs is passed a
 892  * NULL name; some file systems use this operation internally, with varying
 893  * semantics.
 894  */
 895 const char *xattr_full_name(const struct xattr_handler *handler,
 896                             const char *name)
 897 {
 898         size_t prefix_len = strlen(xattr_prefix(handler));
 899
 900         return name - prefix_len;
 901 }
 902 EXPORT_SYMBOL(xattr_full_name);
 903
 904 /*
 905  * Allocate new xattr and copy in the value; but leave the name to callers.
 906  */
 907 struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
 908 {
 909         struct simple_xattr *new_xattr;
 910         size_t len;
 911
 912         /* wrap around? */
 913         len = sizeof(*new_xattr) + size;
 914         if (len < sizeof(*new_xattr))
 915                 return NULL;
 916
 917         new_xattr = kvmalloc(len, GFP_KERNEL);
 918         if (!new_xattr)
 919                 return NULL;
 920
 921         new_xattr->size = size;
 922         memcpy(new_xattr->value, value, size);
 923         return new_xattr;
 924 }
 925
 926 /*
 927  * xattr GET operation for in-memory/pseudo filesystems
 928  */
 929 int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
 930                      void *buffer, size_t size)
 931 {
 932         struct simple_xattr *xattr;
 933         int ret = -ENODATA;
 934
 935         spin_lock(&xattrs->lock);
 936         list_for_each_entry(xattr, &xattrs->head, list) {
 937                 if (strcmp(name, xattr->name))
 938                         continue;
 939
 940                 ret = xattr->size;
 941                 if (buffer) {
 942                         if (size < xattr->size)
 943                                 ret = -ERANGE;
 944                         else
 945                                 memcpy(buffer, xattr->value, xattr->size);
 946                 }
 947                 break;
 948         }
 949         spin_unlock(&xattrs->lock);
 950         return ret;
 951 }
 952
 953 /**
 954  * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
 955  * @xattrs: target simple_xattr list
 956  * @name: name of the extended attribute
 957  * @value: value of the xattr. If %NULL, will remove the attribute.
 958  * @size: size of the new xattr
 959  * @flags: %XATTR_{CREATE|REPLACE}
 960  * @removed_size: returns size of the removed xattr, -1 if none removed
 961  *
 962  * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
 963  * with -EEXIST.  If %XATTR_REPLACE is set, the xattr should exist;
 964  * otherwise, fails with -ENODATA.
 965  *
 966  * Returns 0 on success, -errno on failure.
 967  */
 968 int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
 969                      const void *value, size_t size, int flags,
 970                      ssize_t *removed_size)
 971 {
 972         struct simple_xattr *xattr;
 973         struct simple_xattr *new_xattr = NULL;
 974         int err = 0;
 975
 976         if (removed_size)
 977                 *removed_size = -1;
 978
 979         /* value == NULL means remove */
 980         if (value) {
 981                 new_xattr = simple_xattr_alloc(value, size);
 982                 if (!new_xattr)
 983                         return -ENOMEM;
 984
 985                 new_xattr->name = kstrdup(name, GFP_KERNEL);
 986                 if (!new_xattr->name) {
 987                         kvfree(new_xattr);
 988                         return -ENOMEM;
 989                 }
 990         }
 991
 992         spin_lock(&xattrs->lock);
 993         list_for_each_entry(xattr, &xattrs->head, list) {
 994                 if (!strcmp(name, xattr->name)) {
 995                         if (flags & XATTR_CREATE) {
 996                                 xattr = new_xattr;
 997                                 err = -EEXIST;
 998                         } else if (new_xattr) {
 999                                 list_replace(&xattr->list, &new_xattr->list);
1000                                 if (removed_size)
1001                                         *removed_size = xattr->size;
1002                         } else {
1003                                 list_del(&xattr->list);
1004                                 if (removed_size)
1005                                         *removed_size = xattr->size;
1006                         }
1007                         goto out;
1008                 }
1009         }
1010         if (flags & XATTR_REPLACE) {
1011                 xattr = new_xattr;
1012                 err = -ENODATA;
1013         } else {
1014                 list_add(&new_xattr->list, &xattrs->head);
1015                 xattr = NULL;
1016         }
1017 out:
1018         spin_unlock(&xattrs->lock);
1019         if (xattr) {
1020                 kfree(xattr->name);
1021                 kvfree(xattr);
1022         }
1023         return err;
1024
1025 }
1026
1027 static bool xattr_is_trusted(const char *name)
1028 {
1029         return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
1030 }
1031
1032 static int xattr_list_one(char **buffer, ssize_t *remaining_size,
1033                           const char *name)
1034 {
1035         size_t len = strlen(name) + 1;
1036         if (*buffer) {
1037                 if (*remaining_size < len)
1038                         return -ERANGE;
1039                 memcpy(*buffer, name, len);
1040                 *buffer += len;
1041         }
1042         *remaining_size -= len;
1043         return 0;
1044 }
1045
1046 /*
1047  * xattr LIST operation for in-memory/pseudo filesystems
1048  */
1049 ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs,
1050                           char *buffer, size_t size)
1051 {
1052         bool trusted = capable(CAP_SYS_ADMIN);
1053         struct simple_xattr *xattr;
1054         ssize_t remaining_size = size;
1055         int err = 0;
1056
1057 #ifdef CONFIG_FS_POSIX_ACL
1058         if (IS_POSIXACL(inode)) {
1059                 if (inode->i_acl) {
1060                         err = xattr_list_one(&buffer, &remaining_size,
1061                                              XATTR_NAME_POSIX_ACL_ACCESS);
1062                         if (err)
1063                                 return err;
1064                 }
1065                 if (inode->i_default_acl) {
1066                         err = xattr_list_one(&buffer, &remaining_size,
1067                                              XATTR_NAME_POSIX_ACL_DEFAULT);
1068                         if (err)
1069                                 return err;
1070                 }
1071         }
1072 #endif
1073
1074         spin_lock(&xattrs->lock);
1075         list_for_each_entry(xattr, &xattrs->head, list) {
1076                 /* skip "trusted." attributes for unprivileged callers */
1077                 if (!trusted && xattr_is_trusted(xattr->name))
1078                         continue;
1079
1080                 err = xattr_list_one(&buffer, &remaining_size, xattr->name);
1081                 if (err)
1082                         break;
1083         }
1084         spin_unlock(&xattrs->lock);
1085
1086         return err ? err : size - remaining_size;
1087 }
1088
1089 /*
1090  * Adds an extended attribute to the list
1091  */
1092 void simple_xattr_list_add(struct simple_xattrs *xattrs,
1093                            struct simple_xattr *new_xattr)
1094 {
1095         spin_lock(&xattrs->lock);
1096         list_add(&new_xattr->list, &xattrs->head);
1097         spin_unlock(&xattrs->lock);
1098 }