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