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
  27 static const char *
  28 strcmp_prefix(const char *a, const char *a_prefix)
  29 {
  30         while (*a_prefix && *a == *a_prefix) {
  31                 a++;
  32                 a_prefix++;
  33         }
  34         return *a_prefix ? NULL : a;
  35 }
  36
  37 /*
  38  * In order to implement different sets of xattr operations for each xattr
  39  * prefix, a filesystem should create a null-terminated array of struct
  40  * xattr_handler (one for each prefix) and hang a pointer to it off of the
  41  * s_xattr field of the superblock.
  42  */
  43 #define for_each_xattr_handler(handlers, handler)               \
  44         if (handlers)                                           \
  45                 for ((handler) = *(handlers)++;                 \
  46                         (handler) != NULL;                      \
  47                         (handler) = *(handlers)++)
  48
  49 /*
  50  * Find the xattr_handler with the matching prefix.
  51  */
  52 static const struct xattr_handler *
  53 xattr_resolve_name(struct inode *inode, const char **name)
  54 {
  55         const struct xattr_handler **handlers = inode->i_sb->s_xattr;
  56         const struct xattr_handler *handler;
  57
  58         if (!(inode->i_opflags & IOP_XATTR)) {
  59                 if (unlikely(is_bad_inode(inode)))
  60                         return ERR_PTR(-EIO);
  61                 return ERR_PTR(-EOPNOTSUPP);
  62         }
  63         for_each_xattr_handler(handlers, handler) {
  64                 const char *n;
  65
  66                 n = strcmp_prefix(*name, xattr_prefix(handler));
  67                 if (n) {
  68                         if (!handler->prefix ^ !*n) {
  69                                 if (*n)
  70                                         continue;
  71                                 return ERR_PTR(-EINVAL);
  72                         }
  73                         *name = n;
  74                         return handler;
  75                 }
  76         }
  77         return ERR_PTR(-EOPNOTSUPP);
  78 }
  79
  80 /*
  81  * Check permissions for extended attribute access.  This is a bit complicated
  82  * because different namespaces have very different rules.
  83  */
  84 static int
  85 xattr_permission(struct inode *inode, const char *name, int mask)
  86 {
  87         /*
  88          * We can never set or remove an extended attribute on a read-only
  89          * filesystem  or on an immutable / append-only inode.
  90          */
  91         if (mask & MAY_WRITE) {
  92                 if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
  93                         return -EPERM;
  94                 /*
  95                  * Updating an xattr will likely cause i_uid and i_gid
  96                  * to be writen back improperly if their true value is
  97                  * unknown to the vfs.
  98                  */
  99                 if (HAS_UNMAPPED_ID(inode))
 100                         return -EPERM;
 101         }
 102
 103         /*
 104          * No restriction for security.* and system.* from the VFS.  Decision
 105          * on these is left to the underlying filesystem / security module.
 106          */
 107         if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||
 108             !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
 109                 return 0;
 110
 111         /*
 112          * The trusted.* namespace can only be accessed by privileged users.
 113          */
 114         if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
 115                 if (!capable(CAP_SYS_ADMIN))
 116                         return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
 117                 return 0;
 118         }
 119
 120         /*
 121          * In the user.* namespace, only regular files and directories can have
 122          * extended attributes. For sticky directories, only the owner and
 123          * privileged users can write attributes.
 124          */
 125         if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
 126                 if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
 127                         return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
 128                 if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&
 129                     (mask & MAY_WRITE) && !inode_owner_or_capable(inode))
 130                         return -EPERM;
 131         }
 132
 133         return inode_permission(inode, mask);
 134 }
 135
 136 int
 137 __vfs_setxattr(struct dentry *dentry, struct inode *inode, const char *name,
 138                const void *value, size_t size, int flags)
 139 {
 140         const struct xattr_handler *handler;
 141
 142         handler = xattr_resolve_name(inode, &name);
 143         if (IS_ERR(handler))
 144                 return PTR_ERR(handler);
 145         if (!handler->set)
 146                 return -EOPNOTSUPP;
 147         if (size == 0)
 148                 value = "";  /* empty EA, do not remove */
 149         return handler->set(handler, dentry, inode, name, value, size, flags);
 150 }
 151 EXPORT_SYMBOL(__vfs_setxattr);
 152
 153 /**
 154  *  __vfs_setxattr_noperm - perform setxattr operation without performing
 155  *  permission checks.
 156  *
 157  *  @dentry - object to perform setxattr on
 158  *  @name - xattr name to set
 159  *  @value - value to set @name to
 160  *  @size - size of @value
 161  *  @flags - flags to pass into filesystem operations
 162  *
 163  *  returns the result of the internal setxattr or setsecurity operations.
 164  *
 165  *  This function requires the caller to lock the inode's i_mutex before it
 166  *  is executed. It also assumes that the caller will make the appropriate
 167  *  permission checks.
 168  */
 169 int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
 170                 const void *value, size_t size, int flags)
 171 {
 172         struct inode *inode = dentry->d_inode;
 173         int error = -EAGAIN;
 174         int issec = !strncmp(name, XATTR_SECURITY_PREFIX,
 175                                    XATTR_SECURITY_PREFIX_LEN);
 176
 177         if (issec)
 178                 inode->i_flags &= ~S_NOSEC;
 179         if (inode->i_opflags & IOP_XATTR) {
 180                 error = __vfs_setxattr(dentry, inode, name, value, size, flags);
 181                 if (!error) {
 182                         fsnotify_xattr(dentry);
 183                         security_inode_post_setxattr(dentry, name, value,
 184                                                      size, flags);
 185                 }
 186         } else {
 187                 if (unlikely(is_bad_inode(inode)))
 188                         return -EIO;
 189         }
 190         if (error == -EAGAIN) {
 191                 error = -EOPNOTSUPP;
 192
 193                 if (issec) {
 194                         const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
 195
 196                         error = security_inode_setsecurity(inode, suffix, value,
 197                                                            size, flags);
 198                         if (!error)
 199                                 fsnotify_xattr(dentry);
 200                 }
 201         }
 202
 203         return error;
 204 }
 205
 206
 207 int
 208 vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
 209                 size_t size, int flags)
 210 {
 211         struct inode *inode = dentry->d_inode;
 212         int error;
 213
 214         error = xattr_permission(inode, name, MAY_WRITE);
 215         if (error)
 216                 return error;
 217
 218         inode_lock(inode);
 219         error = security_inode_setxattr(dentry, name, value, size, flags);
 220         if (error)
 221                 goto out;
 222
 223         error = __vfs_setxattr_noperm(dentry, name, value, size, flags);
 224
 225 out:
 226         inode_unlock(inode);
 227         return error;
 228 }
 229 EXPORT_SYMBOL_GPL(vfs_setxattr);
 230
 231 ssize_t
 232 xattr_getsecurity(struct inode *inode, const char *name, void *value,
 233                         size_t size)
 234 {
 235         void *buffer = NULL;
 236         ssize_t len;
 237
 238         if (!value || !size) {
 239                 len = security_inode_getsecurity(inode, name, &buffer, false);
 240                 goto out_noalloc;
 241         }
 242
 243         len = security_inode_getsecurity(inode, name, &buffer, true);
 244         if (len < 0)
 245                 return len;
 246         if (size < len) {
 247                 len = -ERANGE;
 248                 goto out;
 249         }
 250         memcpy(value, buffer, len);
 251 out:
 252         security_release_secctx(buffer, len);
 253 out_noalloc:
 254         return len;
 255 }
 256 EXPORT_SYMBOL_GPL(xattr_getsecurity);
 257
 258 /*
 259  * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
 260  *
 261  * Allocate memory, if not already allocated, or re-allocate correct size,
 262  * before retrieving the extended attribute.
 263  *
 264  * Returns the result of alloc, if failed, or the getxattr operation.
 265  */
 266 ssize_t
 267 vfs_getxattr_alloc(struct dentry *dentry, const char *name, char **xattr_value,
 268                    size_t xattr_size, gfp_t flags)
 269 {
 270         const struct xattr_handler *handler;
 271         struct inode *inode = dentry->d_inode;
 272         char *value = *xattr_value;
 273         int error;
 274
 275         error = xattr_permission(inode, name, MAY_READ);
 276         if (error)
 277                 return error;
 278
 279         handler = xattr_resolve_name(inode, &name);
 280         if (IS_ERR(handler))
 281                 return PTR_ERR(handler);
 282         if (!handler->get)
 283                 return -EOPNOTSUPP;
 284         error = handler->get(handler, dentry, inode, name, NULL, 0);
 285         if (error < 0)
 286                 return error;
 287
 288         if (!value || (error > xattr_size)) {
 289                 value = krealloc(*xattr_value, error + 1, flags);
 290                 if (!value)
 291                         return -ENOMEM;
 292                 memset(value, 0, error + 1);
 293         }
 294
 295         error = handler->get(handler, dentry, inode, name, value, error);
 296         *xattr_value = value;
 297         return error;
 298 }
 299 EXPORT_SYMBOL_GPL(vfs_getxattr_alloc);
 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 = kmalloc(size, GFP_KERNEL | __GFP_NOWARN);
 436                 if (!kvalue) {
 437                         kvalue = vmalloc(size);
 438                         if (!kvalue)
 439                                 return -ENOMEM;
 440                 }
 441                 if (copy_from_user(kvalue, value, size)) {
 442                         error = -EFAULT;
 443                         goto out;
 444                 }
 445                 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
 446                     (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
 447                         posix_acl_fix_xattr_from_user(kvalue, size);
 448         }
 449
 450         error = vfs_setxattr(d, kname, kvalue, size, flags);
 451 out:
 452         kvfree(kvalue);
 453
 454         return error;
 455 }
 456
 457 static int path_setxattr(const char __user *pathname,
 458                          const char __user *name, const void __user *value,
 459                          size_t size, int flags, unsigned int lookup_flags)
 460 {
 461         struct path path;
 462         int error;
 463 retry:
 464         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 465         if (error)
 466                 return error;
 467         error = mnt_want_write(path.mnt);
 468         if (!error) {
 469                 error = setxattr(path.dentry, name, value, size, flags);
 470                 mnt_drop_write(path.mnt);
 471         }
 472         path_put(&path);
 473         if (retry_estale(error, lookup_flags)) {
 474                 lookup_flags |= LOOKUP_REVAL;
 475                 goto retry;
 476         }
 477         return error;
 478 }
 479
 480 SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
 481                 const char __user *, name, const void __user *, value,
 482                 size_t, size, int, flags)
 483 {
 484         return path_setxattr(pathname, name, value, size, flags, LOOKUP_FOLLOW);
 485 }
 486
 487 SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
 488                 const char __user *, name, const void __user *, value,
 489                 size_t, size, int, flags)
 490 {
 491         return path_setxattr(pathname, name, value, size, flags, 0);
 492 }
 493
 494 SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
 495                 const void __user *,value, size_t, size, int, flags)
 496 {
 497         struct fd f = fdget(fd);
 498         int error = -EBADF;
 499
 500         if (!f.file)
 501                 return error;
 502         audit_file(f.file);
 503         error = mnt_want_write_file(f.file);
 504         if (!error) {
 505                 error = setxattr(f.file->f_path.dentry, name, value, size, flags);
 506                 mnt_drop_write_file(f.file);
 507         }
 508         fdput(f);
 509         return error;
 510 }
 511
 512 /*
 513  * Extended attribute GET operations
 514  */
 515 static ssize_t
 516 getxattr(struct dentry *d, const char __user *name, void __user *value,
 517          size_t size)
 518 {
 519         ssize_t error;
 520         void *kvalue = NULL;
 521         char kname[XATTR_NAME_MAX + 1];
 522
 523         error = strncpy_from_user(kname, name, sizeof(kname));
 524         if (error == 0 || error == sizeof(kname))
 525                 error = -ERANGE;
 526         if (error < 0)
 527                 return error;
 528
 529         if (size) {
 530                 if (size > XATTR_SIZE_MAX)
 531                         size = XATTR_SIZE_MAX;
 532                 kvalue = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
 533                 if (!kvalue) {
 534                         kvalue = vmalloc(size);
 535                         if (!kvalue)
 536                                 return -ENOMEM;
 537                 }
 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, size);
 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 = kmalloc(size, __GFP_NOWARN | GFP_KERNEL);
 616                 if (!klist) {
 617                         klist = vmalloc(size);
 618                         if (!klist)
 619                                 return -ENOMEM;
 620                 }
 621         }
 622
 623         error = vfs_listxattr(d, klist, size);
 624         if (error > 0) {
 625                 if (size && copy_to_user(list, klist, error))
 626                         error = -EFAULT;
 627         } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
 628                 /* The file system tried to returned a list bigger
 629                    than XATTR_LIST_MAX bytes. Not possible. */
 630                 error = -E2BIG;
 631         }
 632
 633         kvfree(klist);
 634
 635         return error;
 636 }
 637
 638 static ssize_t path_listxattr(const char __user *pathname, char __user *list,
 639                               size_t size, unsigned int lookup_flags)
 640 {
 641         struct path path;
 642         ssize_t error;
 643 retry:
 644         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 645         if (error)
 646                 return error;
 647         error = listxattr(path.dentry, list, size);
 648         path_put(&path);
 649         if (retry_estale(error, lookup_flags)) {
 650                 lookup_flags |= LOOKUP_REVAL;
 651                 goto retry;
 652         }
 653         return error;
 654 }
 655
 656 SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
 657                 size_t, size)
 658 {
 659         return path_listxattr(pathname, list, size, LOOKUP_FOLLOW);
 660 }
 661
 662 SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
 663                 size_t, size)
 664 {
 665         return path_listxattr(pathname, list, size, 0);
 666 }
 667
 668 SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
 669 {
 670         struct fd f = fdget(fd);
 671         ssize_t error = -EBADF;
 672
 673         if (!f.file)
 674                 return error;
 675         audit_file(f.file);
 676         error = listxattr(f.file->f_path.dentry, list, size);
 677         fdput(f);
 678         return error;
 679 }
 680
 681 /*
 682  * Extended attribute REMOVE operations
 683  */
 684 static long
 685 removexattr(struct dentry *d, const char __user *name)
 686 {
 687         int error;
 688         char kname[XATTR_NAME_MAX + 1];
 689
 690         error = strncpy_from_user(kname, name, sizeof(kname));
 691         if (error == 0 || error == sizeof(kname))
 692                 error = -ERANGE;
 693         if (error < 0)
 694                 return error;
 695
 696         return vfs_removexattr(d, kname);
 697 }
 698
 699 static int path_removexattr(const char __user *pathname,
 700                             const char __user *name, unsigned int lookup_flags)
 701 {
 702         struct path path;
 703         int error;
 704 retry:
 705         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 706         if (error)
 707                 return error;
 708         error = mnt_want_write(path.mnt);
 709         if (!error) {
 710                 error = removexattr(path.dentry, name);
 711                 mnt_drop_write(path.mnt);
 712         }
 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_DEFINE2(removexattr, const char __user *, pathname,
 722                 const char __user *, name)
 723 {
 724         return path_removexattr(pathname, name, LOOKUP_FOLLOW);
 725 }
 726
 727 SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
 728                 const char __user *, name)
 729 {
 730         return path_removexattr(pathname, name, 0);
 731 }
 732
 733 SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
 734 {
 735         struct fd f = fdget(fd);
 736         int error = -EBADF;
 737
 738         if (!f.file)
 739                 return error;
 740         audit_file(f.file);
 741         error = mnt_want_write_file(f.file);
 742         if (!error) {
 743                 error = removexattr(f.file->f_path.dentry, name);
 744                 mnt_drop_write_file(f.file);
 745         }
 746         fdput(f);
 747         return error;
 748 }
 749
 750 /*
 751  * Combine the results of the list() operation from every xattr_handler in the
 752  * list.
 753  */
 754 ssize_t
 755 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 756 {
 757         const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
 758         unsigned int size = 0;
 759
 760         if (!buffer) {
 761                 for_each_xattr_handler(handlers, handler) {
 762                         if (!handler->name ||
 763                             (handler->list && !handler->list(dentry)))
 764                                 continue;
 765                         size += strlen(handler->name) + 1;
 766                 }
 767         } else {
 768                 char *buf = buffer;
 769                 size_t len;
 770
 771                 for_each_xattr_handler(handlers, handler) {
 772                         if (!handler->name ||
 773                             (handler->list && !handler->list(dentry)))
 774                                 continue;
 775                         len = strlen(handler->name);
 776                         if (len + 1 > buffer_size)
 777                                 return -ERANGE;
 778                         memcpy(buf, handler->name, len + 1);
 779                         buf += len + 1;
 780                         buffer_size -= len + 1;
 781                 }
 782                 size = buf - buffer;
 783         }
 784         return size;
 785 }
 786 EXPORT_SYMBOL(generic_listxattr);
 787
 788 /**
 789  * xattr_full_name  -  Compute full attribute name from suffix
 790  *
 791  * @handler:    handler of the xattr_handler operation
 792  * @name:       name passed to the xattr_handler operation
 793  *
 794  * The get and set xattr handler operations are called with the remainder of
 795  * the attribute name after skipping the handler's prefix: for example, "foo"
 796  * is passed to the get operation of a handler with prefix "user." to get
 797  * attribute "user.foo".  The full name is still "there" in the name though.
 798  *
 799  * Note: the list xattr handler operation when called from the vfs is passed a
 800  * NULL name; some file systems use this operation internally, with varying
 801  * semantics.
 802  */
 803 const char *xattr_full_name(const struct xattr_handler *handler,
 804                             const char *name)
 805 {
 806         size_t prefix_len = strlen(xattr_prefix(handler));
 807
 808         return name - prefix_len;
 809 }
 810 EXPORT_SYMBOL(xattr_full_name);
 811
 812 /*
 813  * Allocate new xattr and copy in the value; but leave the name to callers.
 814  */
 815 struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
 816 {
 817         struct simple_xattr *new_xattr;
 818         size_t len;
 819
 820         /* wrap around? */
 821         len = sizeof(*new_xattr) + size;
 822         if (len < sizeof(*new_xattr))
 823                 return NULL;
 824
 825         new_xattr = kmalloc(len, GFP_KERNEL);
 826         if (!new_xattr)
 827                 return NULL;
 828
 829         new_xattr->size = size;
 830         memcpy(new_xattr->value, value, size);
 831         return new_xattr;
 832 }
 833
 834 /*
 835  * xattr GET operation for in-memory/pseudo filesystems
 836  */
 837 int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
 838                      void *buffer, size_t size)
 839 {
 840         struct simple_xattr *xattr;
 841         int ret = -ENODATA;
 842
 843         spin_lock(&xattrs->lock);
 844         list_for_each_entry(xattr, &xattrs->head, list) {
 845                 if (strcmp(name, xattr->name))
 846                         continue;
 847
 848                 ret = xattr->size;
 849                 if (buffer) {
 850                         if (size < xattr->size)
 851                                 ret = -ERANGE;
 852                         else
 853                                 memcpy(buffer, xattr->value, xattr->size);
 854                 }
 855                 break;
 856         }
 857         spin_unlock(&xattrs->lock);
 858         return ret;
 859 }
 860
 861 /**
 862  * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
 863  * @xattrs: target simple_xattr list
 864  * @name: name of the extended attribute
 865  * @value: value of the xattr. If %NULL, will remove the attribute.
 866  * @size: size of the new xattr
 867  * @flags: %XATTR_{CREATE|REPLACE}
 868  *
 869  * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
 870  * with -EEXIST.  If %XATTR_REPLACE is set, the xattr should exist;
 871  * otherwise, fails with -ENODATA.
 872  *
 873  * Returns 0 on success, -errno on failure.
 874  */
 875 int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
 876                      const void *value, size_t size, int flags)
 877 {
 878         struct simple_xattr *xattr;
 879         struct simple_xattr *new_xattr = NULL;
 880         int err = 0;
 881
 882         /* value == NULL means remove */
 883         if (value) {
 884                 new_xattr = simple_xattr_alloc(value, size);
 885                 if (!new_xattr)
 886                         return -ENOMEM;
 887
 888                 new_xattr->name = kstrdup(name, GFP_KERNEL);
 889                 if (!new_xattr->name) {
 890                         kfree(new_xattr);
 891                         return -ENOMEM;
 892                 }
 893         }
 894
 895         spin_lock(&xattrs->lock);
 896         list_for_each_entry(xattr, &xattrs->head, list) {
 897                 if (!strcmp(name, xattr->name)) {
 898                         if (flags & XATTR_CREATE) {
 899                                 xattr = new_xattr;
 900                                 err = -EEXIST;
 901                         } else if (new_xattr) {
 902                                 list_replace(&xattr->list, &new_xattr->list);
 903                         } else {
 904                                 list_del(&xattr->list);
 905                         }
 906                         goto out;
 907                 }
 908         }
 909         if (flags & XATTR_REPLACE) {
 910                 xattr = new_xattr;
 911                 err = -ENODATA;
 912         } else {
 913                 list_add(&new_xattr->list, &xattrs->head);
 914                 xattr = NULL;
 915         }
 916 out:
 917         spin_unlock(&xattrs->lock);
 918         if (xattr) {
 919                 kfree(xattr->name);
 920                 kfree(xattr);
 921         }
 922         return err;
 923
 924 }
 925
 926 static bool xattr_is_trusted(const char *name)
 927 {
 928         return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
 929 }
 930
 931 static int xattr_list_one(char **buffer, ssize_t *remaining_size,
 932                           const char *name)
 933 {
 934         size_t len = strlen(name) + 1;
 935         if (*buffer) {
 936                 if (*remaining_size < len)
 937                         return -ERANGE;
 938                 memcpy(*buffer, name, len);
 939                 *buffer += len;
 940         }
 941         *remaining_size -= len;
 942         return 0;
 943 }
 944
 945 /*
 946  * xattr LIST operation for in-memory/pseudo filesystems
 947  */
 948 ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs,
 949                           char *buffer, size_t size)
 950 {
 951         bool trusted = capable(CAP_SYS_ADMIN);
 952         struct simple_xattr *xattr;
 953         ssize_t remaining_size = size;
 954         int err = 0;
 955
 956 #ifdef CONFIG_FS_POSIX_ACL
 957         if (inode->i_acl) {
 958                 err = xattr_list_one(&buffer, &remaining_size,
 959                                      XATTR_NAME_POSIX_ACL_ACCESS);
 960                 if (err)
 961                         return err;
 962         }
 963         if (inode->i_default_acl) {
 964                 err = xattr_list_one(&buffer, &remaining_size,
 965                                      XATTR_NAME_POSIX_ACL_DEFAULT);
 966                 if (err)
 967                         return err;
 968         }
 969 #endif
 970
 971         spin_lock(&xattrs->lock);
 972         list_for_each_entry(xattr, &xattrs->head, list) {
 973                 /* skip "trusted." attributes for unprivileged callers */
 974                 if (!trusted && xattr_is_trusted(xattr->name))
 975                         continue;
 976
 977                 err = xattr_list_one(&buffer, &remaining_size, xattr->name);
 978                 if (err)
 979                         break;
 980         }
 981         spin_unlock(&xattrs->lock);
 982
 983         return err ? err : size - remaining_size;
 984 }
 985
 986 /*
 987  * Adds an extended attribute to the list
 988  */
 989 void simple_xattr_list_add(struct simple_xattrs *xattrs,
 990                            struct simple_xattr *new_xattr)
 991 {
 992         spin_lock(&xattrs->lock);
 993         list_add(&new_xattr->list, &xattrs->head);
 994         spin_unlock(&xattrs->lock);
 995 }