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