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 <linux/uaccess.h>
  26 #include "internal.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_permission2(ERR_PTR(-EOPNOTSUPP), 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 int
 209 vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
 210                 size_t size, int flags)
 211 {
 212         struct inode *inode = dentry->d_inode;
 213         int error;
 214
 215         error = xattr_permission(inode, name, MAY_WRITE);
 216         if (error)
 217                 return error;
 218
 219         inode_lock(inode);
 220         error = security_inode_setxattr(dentry, name, value, size, flags);
 221         if (error)
 222                 goto out;
 223
 224         error = __vfs_setxattr_noperm(dentry, name, value, size, flags);
 225
 226 out:
 227         inode_unlock(inode);
 228         return error;
 229 }
 230 EXPORT_SYMBOL_GPL(vfs_setxattr);
 231
 232 ssize_t
 233 xattr_getsecurity(struct inode *inode, const char *name, void *value,
 234                         size_t size)
 235 {
 236         void *buffer = NULL;
 237         ssize_t len;
 238
 239         if (!value || !size) {
 240                 len = security_inode_getsecurity(inode, name, &buffer, false);
 241                 goto out_noalloc;
 242         }
 243
 244         len = security_inode_getsecurity(inode, name, &buffer, true);
 245         if (len < 0)
 246                 return len;
 247         if (size < len) {
 248                 len = -ERANGE;
 249                 goto out;
 250         }
 251         memcpy(value, buffer, len);
 252 out:
 253         kfree(buffer);
 254 out_noalloc:
 255         return len;
 256 }
 257 EXPORT_SYMBOL_GPL(xattr_getsecurity);
 258
 259 /*
 260  * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
 261  *
 262  * Allocate memory, if not already allocated, or re-allocate correct size,
 263  * before retrieving the extended attribute.
 264  *
 265  * Returns the result of alloc, if failed, or the getxattr operation.
 266  */
 267 ssize_t
 268 vfs_getxattr_alloc(struct dentry *dentry, const char *name, char **xattr_value,
 269                    size_t xattr_size, gfp_t flags)
 270 {
 271         const struct xattr_handler *handler;
 272         struct inode *inode = dentry->d_inode;
 273         char *value = *xattr_value;
 274         int error;
 275
 276         error = xattr_permission(inode, name, MAY_READ);
 277         if (error)
 278                 return error;
 279
 280         handler = xattr_resolve_name(inode, &name);
 281         if (IS_ERR(handler))
 282                 return PTR_ERR(handler);
 283         if (!handler->get)
 284                 return -EOPNOTSUPP;
 285         error = handler->get(handler, dentry, inode, name, NULL, 0);
 286         if (error < 0)
 287                 return error;
 288
 289         if (!value || (error > xattr_size)) {
 290                 value = krealloc(*xattr_value, error + 1, flags);
 291                 if (!value)
 292                         return -ENOMEM;
 293                 memset(value, 0, error + 1);
 294         }
 295
 296         error = handler->get(handler, dentry, inode, name, value, error);
 297         *xattr_value = value;
 298         return error;
 299 }
 300
 301 ssize_t
 302 __vfs_getxattr(struct dentry *dentry, struct inode *inode, const char *name,
 303                void *value, size_t size)
 304 {
 305         const struct xattr_handler *handler;
 306
 307         handler = xattr_resolve_name(inode, &name);
 308         if (IS_ERR(handler))
 309                 return PTR_ERR(handler);
 310         if (!handler->get)
 311                 return -EOPNOTSUPP;
 312         return handler->get(handler, dentry, inode, name, value, size);
 313 }
 314 EXPORT_SYMBOL(__vfs_getxattr);
 315
 316 ssize_t
 317 vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
 318 {
 319         struct inode *inode = dentry->d_inode;
 320         int error;
 321
 322         error = xattr_permission(inode, name, MAY_READ);
 323         if (error)
 324                 return error;
 325
 326         error = security_inode_getxattr(dentry, name);
 327         if (error)
 328                 return error;
 329
 330         if (!strncmp(name, XATTR_SECURITY_PREFIX,
 331                                 XATTR_SECURITY_PREFIX_LEN)) {
 332                 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
 333                 int ret = xattr_getsecurity(inode, suffix, value, size);
 334                 /*
 335                  * Only overwrite the return value if a security module
 336                  * is actually active.
 337                  */
 338                 if (ret == -EOPNOTSUPP)
 339                         goto nolsm;
 340                 return ret;
 341         }
 342 nolsm:
 343         return __vfs_getxattr(dentry, inode, name, value, size);
 344 }
 345 EXPORT_SYMBOL_GPL(vfs_getxattr);
 346
 347 ssize_t
 348 vfs_listxattr(struct dentry *dentry, char *list, size_t size)
 349 {
 350         struct inode *inode = d_inode(dentry);
 351         ssize_t error;
 352
 353         error = security_inode_listxattr(dentry);
 354         if (error)
 355                 return error;
 356         if (inode->i_op->listxattr && (inode->i_opflags & IOP_XATTR)) {
 357                 error = -EOPNOTSUPP;
 358                 error = inode->i_op->listxattr(dentry, list, size);
 359         } else {
 360                 error = security_inode_listsecurity(inode, list, size);
 361                 if (size && error > size)
 362                         error = -ERANGE;
 363         }
 364         return error;
 365 }
 366 EXPORT_SYMBOL_GPL(vfs_listxattr);
 367
 368 int
 369 __vfs_removexattr(struct dentry *dentry, const char *name)
 370 {
 371         struct inode *inode = d_inode(dentry);
 372         const struct xattr_handler *handler;
 373
 374         handler = xattr_resolve_name(inode, &name);
 375         if (IS_ERR(handler))
 376                 return PTR_ERR(handler);
 377         if (!handler->set)
 378                 return -EOPNOTSUPP;
 379         return handler->set(handler, dentry, inode, name, NULL, 0, XATTR_REPLACE);
 380 }
 381 EXPORT_SYMBOL(__vfs_removexattr);
 382
 383 int
 384 vfs_removexattr(struct dentry *dentry, const char *name)
 385 {
 386         struct inode *inode = dentry->d_inode;
 387         int error;
 388
 389         error = xattr_permission(inode, name, MAY_WRITE);
 390         if (error)
 391                 return error;
 392
 393         inode_lock(inode);
 394         error = security_inode_removexattr(dentry, name);
 395         if (error)
 396                 goto out;
 397
 398         error = __vfs_removexattr(dentry, name);
 399
 400         if (!error) {
 401                 fsnotify_xattr(dentry);
 402                 evm_inode_post_removexattr(dentry, name);
 403         }
 404
 405 out:
 406         inode_unlock(inode);
 407         return error;
 408 }
 409 EXPORT_SYMBOL_GPL(vfs_removexattr);
 410
 411
 412 /*
 413  * Extended attribute SET operations
 414  */
 415 static long
 416 setxattr(struct dentry *d, const char __user *name, const void __user *value,
 417          size_t size, int flags)
 418 {
 419         int error;
 420         void *kvalue = NULL;
 421         char kname[XATTR_NAME_MAX + 1];
 422
 423         if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
 424                 return -EINVAL;
 425
 426         error = strncpy_from_user(kname, name, sizeof(kname));
 427         if (error == 0 || error == sizeof(kname))
 428                 error = -ERANGE;
 429         if (error < 0)
 430                 return error;
 431
 432         if (size) {
 433                 if (size > XATTR_SIZE_MAX)
 434                         return -E2BIG;
 435                 kvalue = kvmalloc(size, GFP_KERNEL);
 436                 if (!kvalue)
 437                         return -ENOMEM;
 438                 if (copy_from_user(kvalue, value, size)) {
 439                         error = -EFAULT;
 440                         goto out;
 441                 }
 442                 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
 443                     (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
 444                         posix_acl_fix_xattr_from_user(kvalue, size);
 445                 else if (strcmp(kname, XATTR_NAME_CAPS) == 0) {
 446                         error = cap_convert_nscap(d, &kvalue, size);
 447                         if (error < 0)
 448                                 goto out;
 449                         size = error;
 450                 }
 451         }
 452
 453         error = vfs_setxattr(d, kname, kvalue, size, flags);
 454 out:
 455         kvfree(kvalue);
 456
 457         return error;
 458 }
 459
 460 static int path_setxattr(const char __user *pathname,
 461                          const char __user *name, const void __user *value,
 462                          size_t size, int flags, unsigned int lookup_flags)
 463 {
 464         struct path path;
 465         int error;
 466 retry:
 467         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 468         if (error)
 469                 return error;
 470         error = mnt_want_write(path.mnt);
 471         if (!error) {
 472                 error = setxattr(path.dentry, name, value, size, flags);
 473                 mnt_drop_write(path.mnt);
 474         }
 475         path_put(&path);
 476         if (retry_estale(error, lookup_flags)) {
 477                 lookup_flags |= LOOKUP_REVAL;
 478                 goto retry;
 479         }
 480         return error;
 481 }
 482
 483 SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
 484                 const char __user *, name, const void __user *, value,
 485                 size_t, size, int, flags)
 486 {
 487         return path_setxattr(pathname, name, value, size, flags, LOOKUP_FOLLOW);
 488 }
 489
 490 SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
 491                 const char __user *, name, const void __user *, value,
 492                 size_t, size, int, flags)
 493 {
 494         return path_setxattr(pathname, name, value, size, flags, 0);
 495 }
 496
 497 SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
 498                 const void __user *,value, size_t, size, int, flags)
 499 {
 500         struct fd f = fdget(fd);
 501         int error = -EBADF;
 502
 503         if (!f.file)
 504                 return error;
 505         audit_file(f.file);
 506         error = mnt_want_write_file_path(f.file);
 507         if (!error) {
 508                 error = setxattr(f.file->f_path.dentry, name, value, size, flags);
 509                 mnt_drop_write_file_path(f.file);
 510         }
 511         fdput(f);
 512         return error;
 513 }
 514
 515 /*
 516  * Extended attribute GET operations
 517  */
 518 static ssize_t
 519 getxattr(struct dentry *d, const char __user *name, void __user *value,
 520          size_t size)
 521 {
 522         ssize_t error;
 523         void *kvalue = NULL;
 524         char kname[XATTR_NAME_MAX + 1];
 525
 526         error = strncpy_from_user(kname, name, sizeof(kname));
 527         if (error == 0 || error == sizeof(kname))
 528                 error = -ERANGE;
 529         if (error < 0)
 530                 return error;
 531
 532         if (size) {
 533                 if (size > XATTR_SIZE_MAX)
 534                         size = XATTR_SIZE_MAX;
 535                 kvalue = kvzalloc(size, GFP_KERNEL);
 536                 if (!kvalue)
 537                         return -ENOMEM;
 538         }
 539
 540         error = vfs_getxattr(d, kname, kvalue, size);
 541         if (error > 0) {
 542                 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
 543                     (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
 544                         posix_acl_fix_xattr_to_user(kvalue, error);
 545                 if (size && copy_to_user(value, kvalue, error))
 546                         error = -EFAULT;
 547         } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
 548                 /* The file system tried to returned a value bigger
 549                    than XATTR_SIZE_MAX bytes. Not possible. */
 550                 error = -E2BIG;
 551         }
 552
 553         kvfree(kvalue);
 554
 555         return error;
 556 }
 557
 558 static ssize_t path_getxattr(const char __user *pathname,
 559                              const char __user *name, void __user *value,
 560                              size_t size, unsigned int lookup_flags)
 561 {
 562         struct path path;
 563         ssize_t error;
 564 retry:
 565         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 566         if (error)
 567                 return error;
 568         error = getxattr(path.dentry, name, value, size);
 569         path_put(&path);
 570         if (retry_estale(error, lookup_flags)) {
 571                 lookup_flags |= LOOKUP_REVAL;
 572                 goto retry;
 573         }
 574         return error;
 575 }
 576
 577 SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
 578                 const char __user *, name, void __user *, value, size_t, size)
 579 {
 580         return path_getxattr(pathname, name, value, size, LOOKUP_FOLLOW);
 581 }
 582
 583 SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
 584                 const char __user *, name, void __user *, value, size_t, size)
 585 {
 586         return path_getxattr(pathname, name, value, size, 0);
 587 }
 588
 589 SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
 590                 void __user *, value, size_t, size)
 591 {
 592         struct fd f = fdget(fd);
 593         ssize_t error = -EBADF;
 594
 595         if (!f.file)
 596                 return error;
 597         audit_file(f.file);
 598         error = getxattr(f.file->f_path.dentry, name, value, size);
 599         fdput(f);
 600         return error;
 601 }
 602
 603 /*
 604  * Extended attribute LIST operations
 605  */
 606 static ssize_t
 607 listxattr(struct dentry *d, char __user *list, size_t size)
 608 {
 609         ssize_t error;
 610         char *klist = NULL;
 611
 612         if (size) {
 613                 if (size > XATTR_LIST_MAX)
 614                         size = XATTR_LIST_MAX;
 615                 klist = kvmalloc(size, GFP_KERNEL);
 616                 if (!klist)
 617                         return -ENOMEM;
 618         }
 619
 620         error = vfs_listxattr(d, klist, size);
 621         if (error > 0) {
 622                 if (size && copy_to_user(list, klist, error))
 623                         error = -EFAULT;
 624         } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
 625                 /* The file system tried to returned a list bigger
 626                    than XATTR_LIST_MAX bytes. Not possible. */
 627                 error = -E2BIG;
 628         }
 629
 630         kvfree(klist);
 631
 632         return error;
 633 }
 634
 635 static ssize_t path_listxattr(const char __user *pathname, char __user *list,
 636                               size_t size, unsigned int lookup_flags)
 637 {
 638         struct path path;
 639         ssize_t error;
 640 retry:
 641         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 642         if (error)
 643                 return error;
 644         error = listxattr(path.dentry, list, size);
 645         path_put(&path);
 646         if (retry_estale(error, lookup_flags)) {
 647                 lookup_flags |= LOOKUP_REVAL;
 648                 goto retry;
 649         }
 650         return error;
 651 }
 652
 653 SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
 654                 size_t, size)
 655 {
 656         return path_listxattr(pathname, list, size, LOOKUP_FOLLOW);
 657 }
 658
 659 SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
 660                 size_t, size)
 661 {
 662         return path_listxattr(pathname, list, size, 0);
 663 }
 664
 665 SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
 666 {
 667         struct fd f = fdget(fd);
 668         ssize_t error = -EBADF;
 669
 670         if (!f.file)
 671                 return error;
 672         audit_file(f.file);
 673         error = listxattr(f.file->f_path.dentry, list, size);
 674         fdput(f);
 675         return error;
 676 }
 677
 678 /*
 679  * Extended attribute REMOVE operations
 680  */
 681 static long
 682 removexattr(struct dentry *d, const char __user *name)
 683 {
 684         int error;
 685         char kname[XATTR_NAME_MAX + 1];
 686
 687         error = strncpy_from_user(kname, name, sizeof(kname));
 688         if (error == 0 || error == sizeof(kname))
 689                 error = -ERANGE;
 690         if (error < 0)
 691                 return error;
 692
 693         return vfs_removexattr(d, kname);
 694 }
 695
 696 static int path_removexattr(const char __user *pathname,
 697                             const char __user *name, unsigned int lookup_flags)
 698 {
 699         struct path path;
 700         int error;
 701 retry:
 702         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 703         if (error)
 704                 return error;
 705         error = mnt_want_write(path.mnt);
 706         if (!error) {
 707                 error = removexattr(path.dentry, name);
 708                 mnt_drop_write(path.mnt);
 709         }
 710         path_put(&path);
 711         if (retry_estale(error, lookup_flags)) {
 712                 lookup_flags |= LOOKUP_REVAL;
 713                 goto retry;
 714         }
 715         return error;
 716 }
 717
 718 SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
 719                 const char __user *, name)
 720 {
 721         return path_removexattr(pathname, name, LOOKUP_FOLLOW);
 722 }
 723
 724 SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
 725                 const char __user *, name)
 726 {
 727         return path_removexattr(pathname, name, 0);
 728 }
 729
 730 SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
 731 {
 732         struct fd f = fdget(fd);
 733         int error = -EBADF;
 734
 735         if (!f.file)
 736                 return error;
 737         audit_file(f.file);
 738         error = mnt_want_write_file_path(f.file);
 739         if (!error) {
 740                 error = removexattr(f.file->f_path.dentry, name);
 741                 mnt_drop_write_file_path(f.file);
 742         }
 743         fdput(f);
 744         return error;
 745 }
 746
 747 /*
 748  * Combine the results of the list() operation from every xattr_handler in the
 749  * list.
 750  */
 751 ssize_t
 752 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 753 {
 754         const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
 755         unsigned int size = 0;
 756
 757         if (!buffer) {
 758                 for_each_xattr_handler(handlers, handler) {
 759                         if (!handler->name ||
 760                             (handler->list && !handler->list(dentry)))
 761                                 continue;
 762                         size += strlen(handler->name) + 1;
 763                 }
 764         } else {
 765                 char *buf = buffer;
 766                 size_t len;
 767
 768                 for_each_xattr_handler(handlers, handler) {
 769                         if (!handler->name ||
 770                             (handler->list && !handler->list(dentry)))
 771                                 continue;
 772                         len = strlen(handler->name);
 773                         if (len + 1 > buffer_size)
 774                                 return -ERANGE;
 775                         memcpy(buf, handler->name, len + 1);
 776                         buf += len + 1;
 777                         buffer_size -= len + 1;
 778                 }
 779                 size = buf - buffer;
 780         }
 781         return size;
 782 }
 783 EXPORT_SYMBOL(generic_listxattr);
 784
 785 /**
 786  * xattr_full_name  -  Compute full attribute name from suffix
 787  *
 788  * @handler:    handler of the xattr_handler operation
 789  * @name:       name passed to the xattr_handler operation
 790  *
 791  * The get and set xattr handler operations are called with the remainder of
 792  * the attribute name after skipping the handler's prefix: for example, "foo"
 793  * is passed to the get operation of a handler with prefix "user." to get
 794  * attribute "user.foo".  The full name is still "there" in the name though.
 795  *
 796  * Note: the list xattr handler operation when called from the vfs is passed a
 797  * NULL name; some file systems use this operation internally, with varying
 798  * semantics.
 799  */
 800 const char *xattr_full_name(const struct xattr_handler *handler,
 801                             const char *name)
 802 {
 803         size_t prefix_len = strlen(xattr_prefix(handler));
 804
 805         return name - prefix_len;
 806 }
 807 EXPORT_SYMBOL(xattr_full_name);
 808
 809 /*
 810  * Allocate new xattr and copy in the value; but leave the name to callers.
 811  */
 812 struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
 813 {
 814         struct simple_xattr *new_xattr;
 815         size_t len;
 816
 817         /* wrap around? */
 818         len = sizeof(*new_xattr) + size;
 819         if (len < sizeof(*new_xattr))
 820                 return NULL;
 821
 822         new_xattr = kmalloc(len, GFP_KERNEL);
 823         if (!new_xattr)
 824                 return NULL;
 825
 826         new_xattr->size = size;
 827         memcpy(new_xattr->value, value, size);
 828         return new_xattr;
 829 }
 830
 831 /*
 832  * xattr GET operation for in-memory/pseudo filesystems
 833  */
 834 int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
 835                      void *buffer, size_t size)
 836 {
 837         struct simple_xattr *xattr;
 838         int ret = -ENODATA;
 839
 840         spin_lock(&xattrs->lock);
 841         list_for_each_entry(xattr, &xattrs->head, list) {
 842                 if (strcmp(name, xattr->name))
 843                         continue;
 844
 845                 ret = xattr->size;
 846                 if (buffer) {
 847                         if (size < xattr->size)
 848                                 ret = -ERANGE;
 849                         else
 850                                 memcpy(buffer, xattr->value, xattr->size);
 851                 }
 852                 break;
 853         }
 854         spin_unlock(&xattrs->lock);
 855         return ret;
 856 }
 857
 858 /**
 859  * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
 860  * @xattrs: target simple_xattr list
 861  * @name: name of the extended attribute
 862  * @value: value of the xattr. If %NULL, will remove the attribute.
 863  * @size: size of the new xattr
 864  * @flags: %XATTR_{CREATE|REPLACE}
 865  *
 866  * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
 867  * with -EEXIST.  If %XATTR_REPLACE is set, the xattr should exist;
 868  * otherwise, fails with -ENODATA.
 869  *
 870  * Returns 0 on success, -errno on failure.
 871  */
 872 int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
 873                      const void *value, size_t size, int flags)
 874 {
 875         struct simple_xattr *xattr;
 876         struct simple_xattr *new_xattr = NULL;
 877         int err = 0;
 878
 879         /* value == NULL means remove */
 880         if (value) {
 881                 new_xattr = simple_xattr_alloc(value, size);
 882                 if (!new_xattr)
 883                         return -ENOMEM;
 884
 885                 new_xattr->name = kstrdup(name, GFP_KERNEL);
 886                 if (!new_xattr->name) {
 887                         kfree(new_xattr);
 888                         return -ENOMEM;
 889                 }
 890         }
 891
 892         spin_lock(&xattrs->lock);
 893         list_for_each_entry(xattr, &xattrs->head, list) {
 894                 if (!strcmp(name, xattr->name)) {
 895                         if (flags & XATTR_CREATE) {
 896                                 xattr = new_xattr;
 897                                 err = -EEXIST;
 898                         } else if (new_xattr) {
 899                                 list_replace(&xattr->list, &new_xattr->list);
 900                         } else {
 901                                 list_del(&xattr->list);
 902                         }
 903                         goto out;
 904                 }
 905         }
 906         if (flags & XATTR_REPLACE) {
 907                 xattr = new_xattr;
 908                 err = -ENODATA;
 909         } else {
 910                 list_add(&new_xattr->list, &xattrs->head);
 911                 xattr = NULL;
 912         }
 913 out:
 914         spin_unlock(&xattrs->lock);
 915         if (xattr) {
 916                 kfree(xattr->name);
 917                 kfree(xattr);
 918         }
 919         return err;
 920
 921 }
 922
 923 static bool xattr_is_trusted(const char *name)
 924 {
 925         return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
 926 }
 927
 928 static int xattr_list_one(char **buffer, ssize_t *remaining_size,
 929                           const char *name)
 930 {
 931         size_t len = strlen(name) + 1;
 932         if (*buffer) {
 933                 if (*remaining_size < len)
 934                         return -ERANGE;
 935                 memcpy(*buffer, name, len);
 936                 *buffer += len;
 937         }
 938         *remaining_size -= len;
 939         return 0;
 940 }
 941
 942 /*
 943  * xattr LIST operation for in-memory/pseudo filesystems
 944  */
 945 ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs,
 946                           char *buffer, size_t size)
 947 {
 948         bool trusted = capable(CAP_SYS_ADMIN);
 949         struct simple_xattr *xattr;
 950         ssize_t remaining_size = size;
 951         int err = 0;
 952
 953 #ifdef CONFIG_FS_POSIX_ACL
 954         if (IS_POSIXACL(inode)) {
 955                 if (inode->i_acl) {
 956                         err = xattr_list_one(&buffer, &remaining_size,
 957                                              XATTR_NAME_POSIX_ACL_ACCESS);
 958                         if (err)
 959                                 return err;
 960                 }
 961                 if (inode->i_default_acl) {
 962                         err = xattr_list_one(&buffer, &remaining_size,
 963                                              XATTR_NAME_POSIX_ACL_DEFAULT);
 964                         if (err)
 965                                 return err;
 966                 }
 967         }
 968 #endif
 969
 970         spin_lock(&xattrs->lock);
 971         list_for_each_entry(xattr, &xattrs->head, list) {
 972                 /* skip "trusted." attributes for unprivileged callers */
 973                 if (!trusted && xattr_is_trusted(xattr->name))
 974                         continue;
 975
 976                 err = xattr_list_one(&buffer, &remaining_size, xattr->name);
 977                 if (err)
 978                         break;
 979         }
 980         spin_unlock(&xattrs->lock);
 981
 982         return err ? err : size - remaining_size;
 983 }
 984
 985 /*
 986  * Adds an extended attribute to the list
 987  */
 988 void simple_xattr_list_add(struct simple_xattrs *xattrs,
 989                            struct simple_xattr *new_xattr)
 990 {
 991         spin_lock(&xattrs->lock);
 992         list_add(&new_xattr->list, &xattrs->head);
 993         spin_unlock(&xattrs->lock);
 994 }