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 EXPORT_SYMBOL_GPL(__vfs_setxattr_noperm);
 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         security_release_secctx(buffer, len);
 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 /**
 369  *  __vfs_removexattr_noperm - perform removexattr operation without
 370  *  performing permission checks.
 371  *
 372  *  @dentry - object to perform setxattr on
 373  *  @name - xattr name to set
 374  *
 375  *  returns the result of the internal setxattr or setsecurity operations.
 376  *
 377  *  This function requires the caller to lock the inode's i_mutex before it
 378  *  is executed. It also assumes that the caller will make the appropriate
 379  *  permission checks.
 380  */
 381 int __vfs_removexattr_noperm(struct dentry *dentry, const char *name)
 382 {
 383         struct inode *inode = dentry->d_inode;
 384         int error = -EOPNOTSUPP;
 385
 386         if (inode->i_op->removexattr) {
 387                 error = inode->i_op->removexattr(dentry, name);
 388                 if (!error) {
 389                         fsnotify_xattr(dentry);
 390                         evm_inode_post_removexattr(dentry, name);
 391                 }
 392         }
 393
 394         return error;
 395 }
 396 EXPORT_SYMBOL_GPL(__vfs_removexattr_noperm);
 397
 398 int
 399 __vfs_removexattr(struct dentry *dentry, const char *name)
 400 {
 401         struct inode *inode = d_inode(dentry);
 402         const struct xattr_handler *handler;
 403
 404         handler = xattr_resolve_name(inode, &name);
 405         if (IS_ERR(handler))
 406                 return PTR_ERR(handler);
 407         if (!handler->set)
 408                 return -EOPNOTSUPP;
 409         return handler->set(handler, dentry, inode, name, NULL, 0, XATTR_REPLACE);
 410 }
 411 EXPORT_SYMBOL(__vfs_removexattr);
 412
 413 int
 414 vfs_removexattr(struct dentry *dentry, const char *name)
 415 {
 416         struct inode *inode = dentry->d_inode;
 417         int error;
 418
 419         error = xattr_permission(inode, name, MAY_WRITE);
 420         if (error)
 421                 return error;
 422
 423         inode_lock(inode);
 424         error = security_inode_removexattr(dentry, name);
 425         if (error)
 426                 goto out;
 427
 428         error = __vfs_removexattr_noperm(dentry, name);
 429
 430         if (!error) {
 431                 fsnotify_xattr(dentry);
 432                 evm_inode_post_removexattr(dentry, name);
 433         }
 434
 435 out:
 436         inode_unlock(inode);
 437         return error;
 438 }
 439 EXPORT_SYMBOL_GPL(vfs_removexattr);
 440
 441
 442 /*
 443  * Extended attribute SET operations
 444  */
 445 static long
 446 setxattr(struct dentry *d, const char __user *name, const void __user *value,
 447          size_t size, int flags)
 448 {
 449         int error;
 450         void *kvalue = NULL;
 451         char kname[XATTR_NAME_MAX + 1];
 452
 453         if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
 454                 return -EINVAL;
 455
 456         error = strncpy_from_user(kname, name, sizeof(kname));
 457         if (error == 0 || error == sizeof(kname))
 458                 error = -ERANGE;
 459         if (error < 0)
 460                 return error;
 461
 462         if (size) {
 463                 if (size > XATTR_SIZE_MAX)
 464                         return -E2BIG;
 465                 kvalue = kmalloc(size, GFP_KERNEL | __GFP_NOWARN);
 466                 if (!kvalue) {
 467                         kvalue = vmalloc(size);
 468                         if (!kvalue)
 469                                 return -ENOMEM;
 470                 }
 471                 if (copy_from_user(kvalue, value, size)) {
 472                         error = -EFAULT;
 473                         goto out;
 474                 }
 475                 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
 476                     (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
 477                         posix_acl_fix_xattr_from_user(kvalue, size);
 478         }
 479
 480         error = vfs_setxattr(d, kname, kvalue, size, flags);
 481 out:
 482         kvfree(kvalue);
 483
 484         return error;
 485 }
 486
 487 static int path_setxattr(const char __user *pathname,
 488                          const char __user *name, const void __user *value,
 489                          size_t size, int flags, unsigned int lookup_flags)
 490 {
 491         struct path path;
 492         int error;
 493 retry:
 494         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 495         if (error)
 496                 return error;
 497         error = mnt_want_write(path.mnt);
 498         if (!error) {
 499                 error = setxattr(path.dentry, name, value, size, flags);
 500                 mnt_drop_write(path.mnt);
 501         }
 502         path_put(&path);
 503         if (retry_estale(error, lookup_flags)) {
 504                 lookup_flags |= LOOKUP_REVAL;
 505                 goto retry;
 506         }
 507         return error;
 508 }
 509
 510 SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
 511                 const char __user *, name, const void __user *, value,
 512                 size_t, size, int, flags)
 513 {
 514         return path_setxattr(pathname, name, value, size, flags, LOOKUP_FOLLOW);
 515 }
 516
 517 SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
 518                 const char __user *, name, const void __user *, value,
 519                 size_t, size, int, flags)
 520 {
 521         return path_setxattr(pathname, name, value, size, flags, 0);
 522 }
 523
 524 SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
 525                 const void __user *,value, size_t, size, int, flags)
 526 {
 527         struct fd f = fdget(fd);
 528         int error = -EBADF;
 529
 530         if (!f.file)
 531                 return error;
 532         audit_file(f.file);
 533         error = mnt_want_write_file(f.file);
 534         if (!error) {
 535                 error = setxattr(f.file->f_path.dentry, name, value, size, flags);
 536                 mnt_drop_write_file(f.file);
 537         }
 538         fdput(f);
 539         return error;
 540 }
 541
 542 /*
 543  * Extended attribute GET operations
 544  */
 545 static ssize_t
 546 getxattr(struct dentry *d, const char __user *name, void __user *value,
 547          size_t size)
 548 {
 549         ssize_t error;
 550         void *kvalue = NULL;
 551         char kname[XATTR_NAME_MAX + 1];
 552
 553         error = strncpy_from_user(kname, name, sizeof(kname));
 554         if (error == 0 || error == sizeof(kname))
 555                 error = -ERANGE;
 556         if (error < 0)
 557                 return error;
 558
 559         if (size) {
 560                 if (size > XATTR_SIZE_MAX)
 561                         size = XATTR_SIZE_MAX;
 562                 kvalue = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
 563                 if (!kvalue) {
 564                         kvalue = vmalloc(size);
 565                         if (!kvalue)
 566                                 return -ENOMEM;
 567                 }
 568         }
 569
 570         error = vfs_getxattr(d, kname, kvalue, size);
 571         if (error > 0) {
 572                 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
 573                     (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
 574                         posix_acl_fix_xattr_to_user(kvalue, size);
 575                 if (size && copy_to_user(value, kvalue, error))
 576                         error = -EFAULT;
 577         } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
 578                 /* The file system tried to returned a value bigger
 579                    than XATTR_SIZE_MAX bytes. Not possible. */
 580                 error = -E2BIG;
 581         }
 582
 583         kvfree(kvalue);
 584
 585         return error;
 586 }
 587
 588 static ssize_t path_getxattr(const char __user *pathname,
 589                              const char __user *name, void __user *value,
 590                              size_t size, unsigned int lookup_flags)
 591 {
 592         struct path path;
 593         ssize_t error;
 594 retry:
 595         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 596         if (error)
 597                 return error;
 598         error = getxattr(path.dentry, name, value, size);
 599         path_put(&path);
 600         if (retry_estale(error, lookup_flags)) {
 601                 lookup_flags |= LOOKUP_REVAL;
 602                 goto retry;
 603         }
 604         return error;
 605 }
 606
 607 SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
 608                 const char __user *, name, void __user *, value, size_t, size)
 609 {
 610         return path_getxattr(pathname, name, value, size, LOOKUP_FOLLOW);
 611 }
 612
 613 SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
 614                 const char __user *, name, void __user *, value, size_t, size)
 615 {
 616         return path_getxattr(pathname, name, value, size, 0);
 617 }
 618
 619 SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
 620                 void __user *, value, size_t, size)
 621 {
 622         struct fd f = fdget(fd);
 623         ssize_t error = -EBADF;
 624
 625         if (!f.file)
 626                 return error;
 627         audit_file(f.file);
 628         error = getxattr(f.file->f_path.dentry, name, value, size);
 629         fdput(f);
 630         return error;
 631 }
 632
 633 /*
 634  * Extended attribute LIST operations
 635  */
 636 static ssize_t
 637 listxattr(struct dentry *d, char __user *list, size_t size)
 638 {
 639         ssize_t error;
 640         char *klist = NULL;
 641
 642         if (size) {
 643                 if (size > XATTR_LIST_MAX)
 644                         size = XATTR_LIST_MAX;
 645                 klist = kmalloc(size, __GFP_NOWARN | GFP_KERNEL);
 646                 if (!klist) {
 647                         klist = vmalloc(size);
 648                         if (!klist)
 649                                 return -ENOMEM;
 650                 }
 651         }
 652
 653         error = vfs_listxattr(d, klist, size);
 654         if (error > 0) {
 655                 if (size && copy_to_user(list, klist, error))
 656                         error = -EFAULT;
 657         } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
 658                 /* The file system tried to returned a list bigger
 659                    than XATTR_LIST_MAX bytes. Not possible. */
 660                 error = -E2BIG;
 661         }
 662
 663         kvfree(klist);
 664
 665         return error;
 666 }
 667
 668 static ssize_t path_listxattr(const char __user *pathname, char __user *list,
 669                               size_t size, unsigned int lookup_flags)
 670 {
 671         struct path path;
 672         ssize_t error;
 673 retry:
 674         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 675         if (error)
 676                 return error;
 677         error = listxattr(path.dentry, list, size);
 678         path_put(&path);
 679         if (retry_estale(error, lookup_flags)) {
 680                 lookup_flags |= LOOKUP_REVAL;
 681                 goto retry;
 682         }
 683         return error;
 684 }
 685
 686 SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
 687                 size_t, size)
 688 {
 689         return path_listxattr(pathname, list, size, LOOKUP_FOLLOW);
 690 }
 691
 692 SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
 693                 size_t, size)
 694 {
 695         return path_listxattr(pathname, list, size, 0);
 696 }
 697
 698 SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
 699 {
 700         struct fd f = fdget(fd);
 701         ssize_t error = -EBADF;
 702
 703         if (!f.file)
 704                 return error;
 705         audit_file(f.file);
 706         error = listxattr(f.file->f_path.dentry, list, size);
 707         fdput(f);
 708         return error;
 709 }
 710
 711 /*
 712  * Extended attribute REMOVE operations
 713  */
 714 static long
 715 removexattr(struct dentry *d, const char __user *name)
 716 {
 717         int error;
 718         char kname[XATTR_NAME_MAX + 1];
 719
 720         error = strncpy_from_user(kname, name, sizeof(kname));
 721         if (error == 0 || error == sizeof(kname))
 722                 error = -ERANGE;
 723         if (error < 0)
 724                 return error;
 725
 726         return vfs_removexattr(d, kname);
 727 }
 728
 729 static int path_removexattr(const char __user *pathname,
 730                             const char __user *name, unsigned int lookup_flags)
 731 {
 732         struct path path;
 733         int error;
 734 retry:
 735         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 736         if (error)
 737                 return error;
 738         error = mnt_want_write(path.mnt);
 739         if (!error) {
 740                 error = removexattr(path.dentry, name);
 741                 mnt_drop_write(path.mnt);
 742         }
 743         path_put(&path);
 744         if (retry_estale(error, lookup_flags)) {
 745                 lookup_flags |= LOOKUP_REVAL;
 746                 goto retry;
 747         }
 748         return error;
 749 }
 750
 751 SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
 752                 const char __user *, name)
 753 {
 754         return path_removexattr(pathname, name, LOOKUP_FOLLOW);
 755 }
 756
 757 SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
 758                 const char __user *, name)
 759 {
 760         return path_removexattr(pathname, name, 0);
 761 }
 762
 763 SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
 764 {
 765         struct fd f = fdget(fd);
 766         int error = -EBADF;
 767
 768         if (!f.file)
 769                 return error;
 770         audit_file(f.file);
 771         error = mnt_want_write_file(f.file);
 772         if (!error) {
 773                 error = removexattr(f.file->f_path.dentry, name);
 774                 mnt_drop_write_file(f.file);
 775         }
 776         fdput(f);
 777         return error;
 778 }
 779
 780 /*
 781  * Combine the results of the list() operation from every xattr_handler in the
 782  * list.
 783  */
 784 ssize_t
 785 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 786 {
 787         const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
 788         unsigned int size = 0;
 789
 790         if (!buffer) {
 791                 for_each_xattr_handler(handlers, handler) {
 792                         if (!handler->name ||
 793                             (handler->list && !handler->list(dentry)))
 794                                 continue;
 795                         size += strlen(handler->name) + 1;
 796                 }
 797         } else {
 798                 char *buf = buffer;
 799                 size_t len;
 800
 801                 for_each_xattr_handler(handlers, handler) {
 802                         if (!handler->name ||
 803                             (handler->list && !handler->list(dentry)))
 804                                 continue;
 805                         len = strlen(handler->name);
 806                         if (len + 1 > buffer_size)
 807                                 return -ERANGE;
 808                         memcpy(buf, handler->name, len + 1);
 809                         buf += len + 1;
 810                         buffer_size -= len + 1;
 811                 }
 812                 size = buf - buffer;
 813         }
 814         return size;
 815 }
 816 EXPORT_SYMBOL(generic_listxattr);
 817
 818 /**
 819  * xattr_full_name  -  Compute full attribute name from suffix
 820  *
 821  * @handler:    handler of the xattr_handler operation
 822  * @name:       name passed to the xattr_handler operation
 823  *
 824  * The get and set xattr handler operations are called with the remainder of
 825  * the attribute name after skipping the handler's prefix: for example, "foo"
 826  * is passed to the get operation of a handler with prefix "user." to get
 827  * attribute "user.foo".  The full name is still "there" in the name though.
 828  *
 829  * Note: the list xattr handler operation when called from the vfs is passed a
 830  * NULL name; some file systems use this operation internally, with varying
 831  * semantics.
 832  */
 833 const char *xattr_full_name(const struct xattr_handler *handler,
 834                             const char *name)
 835 {
 836         size_t prefix_len = strlen(xattr_prefix(handler));
 837
 838         return name - prefix_len;
 839 }
 840 EXPORT_SYMBOL(xattr_full_name);
 841
 842 /*
 843  * Allocate new xattr and copy in the value; but leave the name to callers.
 844  */
 845 struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
 846 {
 847         struct simple_xattr *new_xattr;
 848         size_t len;
 849
 850         /* wrap around? */
 851         len = sizeof(*new_xattr) + size;
 852         if (len < sizeof(*new_xattr))
 853                 return NULL;
 854
 855         new_xattr = kmalloc(len, GFP_KERNEL);
 856         if (!new_xattr)
 857                 return NULL;
 858
 859         new_xattr->size = size;
 860         memcpy(new_xattr->value, value, size);
 861         return new_xattr;
 862 }
 863
 864 /*
 865  * xattr GET operation for in-memory/pseudo filesystems
 866  */
 867 int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
 868                      void *buffer, size_t size)
 869 {
 870         struct simple_xattr *xattr;
 871         int ret = -ENODATA;
 872
 873         spin_lock(&xattrs->lock);
 874         list_for_each_entry(xattr, &xattrs->head, list) {
 875                 if (strcmp(name, xattr->name))
 876                         continue;
 877
 878                 ret = xattr->size;
 879                 if (buffer) {
 880                         if (size < xattr->size)
 881                                 ret = -ERANGE;
 882                         else
 883                                 memcpy(buffer, xattr->value, xattr->size);
 884                 }
 885                 break;
 886         }
 887         spin_unlock(&xattrs->lock);
 888         return ret;
 889 }
 890
 891 /**
 892  * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
 893  * @xattrs: target simple_xattr list
 894  * @name: name of the extended attribute
 895  * @value: value of the xattr. If %NULL, will remove the attribute.
 896  * @size: size of the new xattr
 897  * @flags: %XATTR_{CREATE|REPLACE}
 898  *
 899  * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
 900  * with -EEXIST.  If %XATTR_REPLACE is set, the xattr should exist;
 901  * otherwise, fails with -ENODATA.
 902  *
 903  * Returns 0 on success, -errno on failure.
 904  */
 905 int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
 906                      const void *value, size_t size, int flags)
 907 {
 908         struct simple_xattr *xattr;
 909         struct simple_xattr *new_xattr = NULL;
 910         int err = 0;
 911
 912         /* value == NULL means remove */
 913         if (value) {
 914                 new_xattr = simple_xattr_alloc(value, size);
 915                 if (!new_xattr)
 916                         return -ENOMEM;
 917
 918                 new_xattr->name = kstrdup(name, GFP_KERNEL);
 919                 if (!new_xattr->name) {
 920                         kfree(new_xattr);
 921                         return -ENOMEM;
 922                 }
 923         }
 924
 925         spin_lock(&xattrs->lock);
 926         list_for_each_entry(xattr, &xattrs->head, list) {
 927                 if (!strcmp(name, xattr->name)) {
 928                         if (flags & XATTR_CREATE) {
 929                                 xattr = new_xattr;
 930                                 err = -EEXIST;
 931                         } else if (new_xattr) {
 932                                 list_replace(&xattr->list, &new_xattr->list);
 933                         } else {
 934                                 list_del(&xattr->list);
 935                         }
 936                         goto out;
 937                 }
 938         }
 939         if (flags & XATTR_REPLACE) {
 940                 xattr = new_xattr;
 941                 err = -ENODATA;
 942         } else {
 943                 list_add(&new_xattr->list, &xattrs->head);
 944                 xattr = NULL;
 945         }
 946 out:
 947         spin_unlock(&xattrs->lock);
 948         if (xattr) {
 949                 kfree(xattr->name);
 950                 kfree(xattr);
 951         }
 952         return err;
 953
 954 }
 955
 956 static bool xattr_is_trusted(const char *name)
 957 {
 958         return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
 959 }
 960
 961 static int xattr_list_one(char **buffer, ssize_t *remaining_size,
 962                           const char *name)
 963 {
 964         size_t len = strlen(name) + 1;
 965         if (*buffer) {
 966                 if (*remaining_size < len)
 967                         return -ERANGE;
 968                 memcpy(*buffer, name, len);
 969                 *buffer += len;
 970         }
 971         *remaining_size -= len;
 972         return 0;
 973 }
 974
 975 /*
 976  * xattr LIST operation for in-memory/pseudo filesystems
 977  */
 978 ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs,
 979                           char *buffer, size_t size)
 980 {
 981         bool trusted = capable(CAP_SYS_ADMIN);
 982         struct simple_xattr *xattr;
 983         ssize_t remaining_size = size;
 984         int err = 0;
 985
 986 #ifdef CONFIG_FS_POSIX_ACL
 987         if (inode->i_acl) {
 988                 err = xattr_list_one(&buffer, &remaining_size,
 989                                      XATTR_NAME_POSIX_ACL_ACCESS);
 990                 if (err)
 991                         return err;
 992         }
 993         if (inode->i_default_acl) {
 994                 err = xattr_list_one(&buffer, &remaining_size,
 995                                      XATTR_NAME_POSIX_ACL_DEFAULT);
 996                 if (err)
 997                         return err;
 998         }
 999 #endif
1000
1001         spin_lock(&xattrs->lock);
1002         list_for_each_entry(xattr, &xattrs->head, list) {
1003                 /* skip "trusted." attributes for unprivileged callers */
1004                 if (!trusted && xattr_is_trusted(xattr->name))
1005                         continue;
1006
1007                 err = xattr_list_one(&buffer, &remaining_size, xattr->name);
1008                 if (err)
1009                         break;
1010         }
1011         spin_unlock(&xattrs->lock);
1012
1013         return err ? err : size - remaining_size;
1014 }
1015
1016 /*
1017  * Adds an extended attribute to the list
1018  */
1019 void simple_xattr_list_add(struct simple_xattrs *xattrs,
1020                            struct simple_xattr *new_xattr)
1021 {
1022         spin_lock(&xattrs->lock);
1023         list_add(&new_xattr->list, &xattrs->head);
1024         spin_unlock(&xattrs->lock);
1025 }