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  * __vfs_setxattr_locked: set an extended attribute while holding the inode
 208  * lock
 209  *
 210  *  @dentry - object to perform setxattr on
 211  *  @name - xattr name to set
 212  *  @value - value to set @name to
 213  *  @size - size of @value
 214  *  @flags - flags to pass into filesystem operations
 215  *  @delegated_inode - on return, will contain an inode pointer that
 216  *  a delegation was broken on, NULL if none.
 217  */
 218 int
 219 __vfs_setxattr_locked(struct dentry *dentry, const char *name,
 220                 const void *value, size_t size, int flags,
 221                 struct inode **delegated_inode)
 222 {
 223         struct inode *inode = dentry->d_inode;
 224         int error;
 225
 226         error = xattr_permission(inode, name, MAY_WRITE);
 227         if (error)
 228                 return error;
 229
 230         error = security_inode_setxattr(dentry, name, value, size, flags);
 231         if (error)
 232                 goto out;
 233
 234         error = try_break_deleg(inode, delegated_inode);
 235         if (error)
 236                 goto out;
 237
 238         error = __vfs_setxattr_noperm(dentry, name, value, size, flags);
 239
 240 out:
 241         return error;
 242 }
 243 EXPORT_SYMBOL_GPL(__vfs_setxattr_locked);
 244
 245 int
 246 vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
 247                 size_t size, int flags)
 248 {
 249         struct inode *inode = dentry->d_inode;
 250         struct inode *delegated_inode = NULL;
 251         int error;
 252
 253 retry_deleg:
 254         inode_lock(inode);
 255         error = __vfs_setxattr_locked(dentry, name, value, size, flags,
 256             &delegated_inode);
 257         inode_unlock(inode);
 258
 259         if (delegated_inode) {
 260                 error = break_deleg_wait(&delegated_inode);
 261                 if (!error)
 262                         goto retry_deleg;
 263         }
 264         return error;
 265 }
 266 EXPORT_SYMBOL_GPL(vfs_setxattr);
 267
 268 static ssize_t
 269 xattr_getsecurity(struct inode *inode, const char *name, void *value,
 270                         size_t size)
 271 {
 272         void *buffer = NULL;
 273         ssize_t len;
 274
 275         if (!value || !size) {
 276                 len = security_inode_getsecurity(inode, name, &buffer, false);
 277                 goto out_noalloc;
 278         }
 279
 280         len = security_inode_getsecurity(inode, name, &buffer, true);
 281         if (len < 0)
 282                 return len;
 283         if (size < len) {
 284                 len = -ERANGE;
 285                 goto out;
 286         }
 287         memcpy(value, buffer, len);
 288 out:
 289         kfree(buffer);
 290 out_noalloc:
 291         return len;
 292 }
 293
 294 /*
 295  * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
 296  *
 297  * Allocate memory, if not already allocated, or re-allocate correct size,
 298  * before retrieving the extended attribute.
 299  *
 300  * Returns the result of alloc, if failed, or the getxattr operation.
 301  */
 302 ssize_t
 303 vfs_getxattr_alloc(struct dentry *dentry, const char *name, char **xattr_value,
 304                    size_t xattr_size, gfp_t flags)
 305 {
 306         const struct xattr_handler *handler;
 307         struct inode *inode = dentry->d_inode;
 308         char *value = *xattr_value;
 309         int error;
 310
 311         error = xattr_permission(inode, name, MAY_READ);
 312         if (error)
 313                 return error;
 314
 315         handler = xattr_resolve_name(inode, &name);
 316         if (IS_ERR(handler))
 317                 return PTR_ERR(handler);
 318         if (!handler->get)
 319                 return -EOPNOTSUPP;
 320         error = handler->get(handler, dentry, inode, name, NULL, 0);
 321         if (error < 0)
 322                 return error;
 323
 324         if (!value || (error > xattr_size)) {
 325                 value = krealloc(*xattr_value, error + 1, flags);
 326                 if (!value)
 327                         return -ENOMEM;
 328                 memset(value, 0, error + 1);
 329         }
 330
 331         error = handler->get(handler, dentry, inode, name, value, error);
 332         *xattr_value = value;
 333         return error;
 334 }
 335
 336 ssize_t
 337 __vfs_getxattr(struct dentry *dentry, struct inode *inode, const char *name,
 338                void *value, size_t size)
 339 {
 340         const struct xattr_handler *handler;
 341
 342         handler = xattr_resolve_name(inode, &name);
 343         if (IS_ERR(handler))
 344                 return PTR_ERR(handler);
 345         if (!handler->get)
 346                 return -EOPNOTSUPP;
 347         return handler->get(handler, dentry, inode, name, value, size);
 348 }
 349 EXPORT_SYMBOL(__vfs_getxattr);
 350
 351 ssize_t
 352 vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
 353 {
 354         struct inode *inode = dentry->d_inode;
 355         int error;
 356
 357         error = xattr_permission(inode, name, MAY_READ);
 358         if (error)
 359                 return error;
 360
 361         error = security_inode_getxattr(dentry, name);
 362         if (error)
 363                 return error;
 364
 365         if (!strncmp(name, XATTR_SECURITY_PREFIX,
 366                                 XATTR_SECURITY_PREFIX_LEN)) {
 367                 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
 368                 int ret = xattr_getsecurity(inode, suffix, value, size);
 369                 /*
 370                  * Only overwrite the return value if a security module
 371                  * is actually active.
 372                  */
 373                 if (ret == -EOPNOTSUPP)
 374                         goto nolsm;
 375                 return ret;
 376         }
 377 nolsm:
 378         return __vfs_getxattr(dentry, inode, name, value, size);
 379 }
 380 EXPORT_SYMBOL_GPL(vfs_getxattr);
 381
 382 ssize_t
 383 vfs_listxattr(struct dentry *dentry, char *list, size_t size)
 384 {
 385         struct inode *inode = d_inode(dentry);
 386         ssize_t error;
 387
 388         error = security_inode_listxattr(dentry);
 389         if (error)
 390                 return error;
 391         if (inode->i_op->listxattr && (inode->i_opflags & IOP_XATTR)) {
 392                 error = inode->i_op->listxattr(dentry, list, size);
 393         } else {
 394                 error = security_inode_listsecurity(inode, list, size);
 395                 if (size && error > size)
 396                         error = -ERANGE;
 397         }
 398         return error;
 399 }
 400 EXPORT_SYMBOL_GPL(vfs_listxattr);
 401
 402 int
 403 __vfs_removexattr(struct dentry *dentry, const char *name)
 404 {
 405         struct inode *inode = d_inode(dentry);
 406         const struct xattr_handler *handler;
 407
 408         handler = xattr_resolve_name(inode, &name);
 409         if (IS_ERR(handler))
 410                 return PTR_ERR(handler);
 411         if (!handler->set)
 412                 return -EOPNOTSUPP;
 413         return handler->set(handler, dentry, inode, name, NULL, 0, XATTR_REPLACE);
 414 }
 415 EXPORT_SYMBOL(__vfs_removexattr);
 416
 417 /**
 418  * __vfs_removexattr_locked: set an extended attribute while holding the inode
 419  * lock
 420  *
 421  *  @dentry - object to perform setxattr on
 422  *  @name - name of xattr to remove
 423  *  @delegated_inode - on return, will contain an inode pointer that
 424  *  a delegation was broken on, NULL if none.
 425  */
 426 int
 427 __vfs_removexattr_locked(struct dentry *dentry, const char *name,
 428                 struct inode **delegated_inode)
 429 {
 430         struct inode *inode = dentry->d_inode;
 431         int error;
 432
 433         error = xattr_permission(inode, name, MAY_WRITE);
 434         if (error)
 435                 return error;
 436
 437         error = security_inode_removexattr(dentry, name);
 438         if (error)
 439                 goto out;
 440
 441         error = try_break_deleg(inode, delegated_inode);
 442         if (error)
 443                 goto out;
 444
 445         error = __vfs_removexattr(dentry, name);
 446
 447         if (!error) {
 448                 fsnotify_xattr(dentry);
 449                 evm_inode_post_removexattr(dentry, name);
 450         }
 451
 452 out:
 453         return error;
 454 }
 455 EXPORT_SYMBOL_GPL(__vfs_removexattr_locked);
 456
 457 int
 458 vfs_removexattr(struct dentry *dentry, const char *name)
 459 {
 460         struct inode *inode = dentry->d_inode;
 461         struct inode *delegated_inode = NULL;
 462         int error;
 463
 464 retry_deleg:
 465         inode_lock(inode);
 466         error = __vfs_removexattr_locked(dentry, name, &delegated_inode);
 467         inode_unlock(inode);
 468
 469         if (delegated_inode) {
 470                 error = break_deleg_wait(&delegated_inode);
 471                 if (!error)
 472                         goto retry_deleg;
 473         }
 474
 475         return error;
 476 }
 477 EXPORT_SYMBOL_GPL(vfs_removexattr);
 478
 479 /*
 480  * Extended attribute SET operations
 481  */
 482 static long
 483 setxattr(struct dentry *d, const char __user *name, const void __user *value,
 484          size_t size, int flags)
 485 {
 486         int error;
 487         void *kvalue = NULL;
 488         char kname[XATTR_NAME_MAX + 1];
 489
 490         if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
 491                 return -EINVAL;
 492
 493         error = strncpy_from_user(kname, name, sizeof(kname));
 494         if (error == 0 || error == sizeof(kname))
 495                 error = -ERANGE;
 496         if (error < 0)
 497                 return error;
 498
 499         if (size) {
 500                 if (size > XATTR_SIZE_MAX)
 501                         return -E2BIG;
 502                 kvalue = kvmalloc(size, GFP_KERNEL);
 503                 if (!kvalue)
 504                         return -ENOMEM;
 505                 if (copy_from_user(kvalue, value, size)) {
 506                         error = -EFAULT;
 507                         goto out;
 508                 }
 509                 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
 510                     (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
 511                         posix_acl_fix_xattr_from_user(kvalue, size);
 512                 else if (strcmp(kname, XATTR_NAME_CAPS) == 0) {
 513                         error = cap_convert_nscap(d, &kvalue, size);
 514                         if (error < 0)
 515                                 goto out;
 516                         size = error;
 517                 }
 518         }
 519
 520         error = vfs_setxattr(d, kname, kvalue, size, flags);
 521 out:
 522         kvfree(kvalue);
 523
 524         return error;
 525 }
 526
 527 static int path_setxattr(const char __user *pathname,
 528                          const char __user *name, const void __user *value,
 529                          size_t size, int flags, unsigned int lookup_flags)
 530 {
 531         struct path path;
 532         int error;
 533 retry:
 534         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 535         if (error)
 536                 return error;
 537         error = mnt_want_write(path.mnt);
 538         if (!error) {
 539                 error = setxattr(path.dentry, name, value, size, flags);
 540                 mnt_drop_write(path.mnt);
 541         }
 542         path_put(&path);
 543         if (retry_estale(error, lookup_flags)) {
 544                 lookup_flags |= LOOKUP_REVAL;
 545                 goto retry;
 546         }
 547         return error;
 548 }
 549
 550 SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
 551                 const char __user *, name, const void __user *, value,
 552                 size_t, size, int, flags)
 553 {
 554         return path_setxattr(pathname, name, value, size, flags, LOOKUP_FOLLOW);
 555 }
 556
 557 SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
 558                 const char __user *, name, const void __user *, value,
 559                 size_t, size, int, flags)
 560 {
 561         return path_setxattr(pathname, name, value, size, flags, 0);
 562 }
 563
 564 SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
 565                 const void __user *,value, size_t, size, int, flags)
 566 {
 567         struct fd f = fdget(fd);
 568         int error = -EBADF;
 569
 570         if (!f.file)
 571                 return error;
 572         audit_file(f.file);
 573         error = mnt_want_write_file(f.file);
 574         if (!error) {
 575                 error = setxattr(f.file->f_path.dentry, name, value, size, flags);
 576                 mnt_drop_write_file(f.file);
 577         }
 578         fdput(f);
 579         return error;
 580 }
 581
 582 /*
 583  * Extended attribute GET operations
 584  */
 585 static ssize_t
 586 getxattr(struct dentry *d, const char __user *name, void __user *value,
 587          size_t size)
 588 {
 589         ssize_t error;
 590         void *kvalue = NULL;
 591         char kname[XATTR_NAME_MAX + 1];
 592
 593         error = strncpy_from_user(kname, name, sizeof(kname));
 594         if (error == 0 || error == sizeof(kname))
 595                 error = -ERANGE;
 596         if (error < 0)
 597                 return error;
 598
 599         if (size) {
 600                 if (size > XATTR_SIZE_MAX)
 601                         size = XATTR_SIZE_MAX;
 602                 kvalue = kvzalloc(size, GFP_KERNEL);
 603                 if (!kvalue)
 604                         return -ENOMEM;
 605         }
 606
 607         error = vfs_getxattr(d, kname, kvalue, size);
 608         if (error > 0) {
 609                 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
 610                     (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
 611                         posix_acl_fix_xattr_to_user(kvalue, error);
 612                 if (size && copy_to_user(value, kvalue, error))
 613                         error = -EFAULT;
 614         } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
 615                 /* The file system tried to returned a value bigger
 616                    than XATTR_SIZE_MAX bytes. Not possible. */
 617                 error = -E2BIG;
 618         }
 619
 620         kvfree(kvalue);
 621
 622         return error;
 623 }
 624
 625 static ssize_t path_getxattr(const char __user *pathname,
 626                              const char __user *name, void __user *value,
 627                              size_t size, unsigned int lookup_flags)
 628 {
 629         struct path path;
 630         ssize_t error;
 631 retry:
 632         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 633         if (error)
 634                 return error;
 635         error = getxattr(path.dentry, name, value, size);
 636         path_put(&path);
 637         if (retry_estale(error, lookup_flags)) {
 638                 lookup_flags |= LOOKUP_REVAL;
 639                 goto retry;
 640         }
 641         return error;
 642 }
 643
 644 SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
 645                 const char __user *, name, void __user *, value, size_t, size)
 646 {
 647         return path_getxattr(pathname, name, value, size, LOOKUP_FOLLOW);
 648 }
 649
 650 SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
 651                 const char __user *, name, void __user *, value, size_t, size)
 652 {
 653         return path_getxattr(pathname, name, value, size, 0);
 654 }
 655
 656 SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
 657                 void __user *, value, size_t, size)
 658 {
 659         struct fd f = fdget(fd);
 660         ssize_t error = -EBADF;
 661
 662         if (!f.file)
 663                 return error;
 664         audit_file(f.file);
 665         error = getxattr(f.file->f_path.dentry, name, value, size);
 666         fdput(f);
 667         return error;
 668 }
 669
 670 /*
 671  * Extended attribute LIST operations
 672  */
 673 static ssize_t
 674 listxattr(struct dentry *d, char __user *list, size_t size)
 675 {
 676         ssize_t error;
 677         char *klist = NULL;
 678
 679         if (size) {
 680                 if (size > XATTR_LIST_MAX)
 681                         size = XATTR_LIST_MAX;
 682                 klist = kvmalloc(size, GFP_KERNEL);
 683                 if (!klist)
 684                         return -ENOMEM;
 685         }
 686
 687         error = vfs_listxattr(d, klist, size);
 688         if (error > 0) {
 689                 if (size && copy_to_user(list, klist, error))
 690                         error = -EFAULT;
 691         } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
 692                 /* The file system tried to returned a list bigger
 693                    than XATTR_LIST_MAX bytes. Not possible. */
 694                 error = -E2BIG;
 695         }
 696
 697         kvfree(klist);
 698
 699         return error;
 700 }
 701
 702 static ssize_t path_listxattr(const char __user *pathname, char __user *list,
 703                               size_t size, unsigned int lookup_flags)
 704 {
 705         struct path path;
 706         ssize_t error;
 707 retry:
 708         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 709         if (error)
 710                 return error;
 711         error = listxattr(path.dentry, list, size);
 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_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
 721                 size_t, size)
 722 {
 723         return path_listxattr(pathname, list, size, LOOKUP_FOLLOW);
 724 }
 725
 726 SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
 727                 size_t, size)
 728 {
 729         return path_listxattr(pathname, list, size, 0);
 730 }
 731
 732 SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
 733 {
 734         struct fd f = fdget(fd);
 735         ssize_t error = -EBADF;
 736
 737         if (!f.file)
 738                 return error;
 739         audit_file(f.file);
 740         error = listxattr(f.file->f_path.dentry, list, size);
 741         fdput(f);
 742         return error;
 743 }
 744
 745 /*
 746  * Extended attribute REMOVE operations
 747  */
 748 static long
 749 removexattr(struct dentry *d, const char __user *name)
 750 {
 751         int error;
 752         char kname[XATTR_NAME_MAX + 1];
 753
 754         error = strncpy_from_user(kname, name, sizeof(kname));
 755         if (error == 0 || error == sizeof(kname))
 756                 error = -ERANGE;
 757         if (error < 0)
 758                 return error;
 759
 760         return vfs_removexattr(d, kname);
 761 }
 762
 763 static int path_removexattr(const char __user *pathname,
 764                             const char __user *name, unsigned int lookup_flags)
 765 {
 766         struct path path;
 767         int error;
 768 retry:
 769         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 770         if (error)
 771                 return error;
 772         error = mnt_want_write(path.mnt);
 773         if (!error) {
 774                 error = removexattr(path.dentry, name);
 775                 mnt_drop_write(path.mnt);
 776         }
 777         path_put(&path);
 778         if (retry_estale(error, lookup_flags)) {
 779                 lookup_flags |= LOOKUP_REVAL;
 780                 goto retry;
 781         }
 782         return error;
 783 }
 784
 785 SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
 786                 const char __user *, name)
 787 {
 788         return path_removexattr(pathname, name, LOOKUP_FOLLOW);
 789 }
 790
 791 SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
 792                 const char __user *, name)
 793 {
 794         return path_removexattr(pathname, name, 0);
 795 }
 796
 797 SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
 798 {
 799         struct fd f = fdget(fd);
 800         int error = -EBADF;
 801
 802         if (!f.file)
 803                 return error;
 804         audit_file(f.file);
 805         error = mnt_want_write_file(f.file);
 806         if (!error) {
 807                 error = removexattr(f.file->f_path.dentry, name);
 808                 mnt_drop_write_file(f.file);
 809         }
 810         fdput(f);
 811         return error;
 812 }
 813
 814 /*
 815  * Combine the results of the list() operation from every xattr_handler in the
 816  * list.
 817  */
 818 ssize_t
 819 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 820 {
 821         const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
 822         unsigned int size = 0;
 823
 824         if (!buffer) {
 825                 for_each_xattr_handler(handlers, handler) {
 826                         if (!handler->name ||
 827                             (handler->list && !handler->list(dentry)))
 828                                 continue;
 829                         size += strlen(handler->name) + 1;
 830                 }
 831         } else {
 832                 char *buf = buffer;
 833                 size_t len;
 834
 835                 for_each_xattr_handler(handlers, handler) {
 836                         if (!handler->name ||
 837                             (handler->list && !handler->list(dentry)))
 838                                 continue;
 839                         len = strlen(handler->name);
 840                         if (len + 1 > buffer_size)
 841                                 return -ERANGE;
 842                         memcpy(buf, handler->name, len + 1);
 843                         buf += len + 1;
 844                         buffer_size -= len + 1;
 845                 }
 846                 size = buf - buffer;
 847         }
 848         return size;
 849 }
 850 EXPORT_SYMBOL(generic_listxattr);
 851
 852 /**
 853  * xattr_full_name  -  Compute full attribute name from suffix
 854  *
 855  * @handler:    handler of the xattr_handler operation
 856  * @name:       name passed to the xattr_handler operation
 857  *
 858  * The get and set xattr handler operations are called with the remainder of
 859  * the attribute name after skipping the handler's prefix: for example, "foo"
 860  * is passed to the get operation of a handler with prefix "user." to get
 861  * attribute "user.foo".  The full name is still "there" in the name though.
 862  *
 863  * Note: the list xattr handler operation when called from the vfs is passed a
 864  * NULL name; some file systems use this operation internally, with varying
 865  * semantics.
 866  */
 867 const char *xattr_full_name(const struct xattr_handler *handler,
 868                             const char *name)
 869 {
 870         size_t prefix_len = strlen(xattr_prefix(handler));
 871
 872         return name - prefix_len;
 873 }
 874 EXPORT_SYMBOL(xattr_full_name);
 875
 876 /*
 877  * Allocate new xattr and copy in the value; but leave the name to callers.
 878  */
 879 struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
 880 {
 881         struct simple_xattr *new_xattr;
 882         size_t len;
 883
 884         /* wrap around? */
 885         len = sizeof(*new_xattr) + size;
 886         if (len < sizeof(*new_xattr))
 887                 return NULL;
 888
 889         new_xattr = kmalloc(len, GFP_KERNEL);
 890         if (!new_xattr)
 891                 return NULL;
 892
 893         new_xattr->size = size;
 894         memcpy(new_xattr->value, value, size);
 895         return new_xattr;
 896 }
 897
 898 /*
 899  * xattr GET operation for in-memory/pseudo filesystems
 900  */
 901 int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
 902                      void *buffer, size_t size)
 903 {
 904         struct simple_xattr *xattr;
 905         int ret = -ENODATA;
 906
 907         spin_lock(&xattrs->lock);
 908         list_for_each_entry(xattr, &xattrs->head, list) {
 909                 if (strcmp(name, xattr->name))
 910                         continue;
 911
 912                 ret = xattr->size;
 913                 if (buffer) {
 914                         if (size < xattr->size)
 915                                 ret = -ERANGE;
 916                         else
 917                                 memcpy(buffer, xattr->value, xattr->size);
 918                 }
 919                 break;
 920         }
 921         spin_unlock(&xattrs->lock);
 922         return ret;
 923 }
 924
 925 /**
 926  * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
 927  * @xattrs: target simple_xattr list
 928  * @name: name of the extended attribute
 929  * @value: value of the xattr. If %NULL, will remove the attribute.
 930  * @size: size of the new xattr
 931  * @flags: %XATTR_{CREATE|REPLACE}
 932  *
 933  * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
 934  * with -EEXIST.  If %XATTR_REPLACE is set, the xattr should exist;
 935  * otherwise, fails with -ENODATA.
 936  *
 937  * Returns 0 on success, -errno on failure.
 938  */
 939 int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
 940                      const void *value, size_t size, int flags)
 941 {
 942         struct simple_xattr *xattr;
 943         struct simple_xattr *new_xattr = NULL;
 944         int err = 0;
 945
 946         /* value == NULL means remove */
 947         if (value) {
 948                 new_xattr = simple_xattr_alloc(value, size);
 949                 if (!new_xattr)
 950                         return -ENOMEM;
 951
 952                 new_xattr->name = kstrdup(name, GFP_KERNEL);
 953                 if (!new_xattr->name) {
 954                         kfree(new_xattr);
 955                         return -ENOMEM;
 956                 }
 957         }
 958
 959         spin_lock(&xattrs->lock);
 960         list_for_each_entry(xattr, &xattrs->head, list) {
 961                 if (!strcmp(name, xattr->name)) {
 962                         if (flags & XATTR_CREATE) {
 963                                 xattr = new_xattr;
 964                                 err = -EEXIST;
 965                         } else if (new_xattr) {
 966                                 list_replace(&xattr->list, &new_xattr->list);
 967                         } else {
 968                                 list_del(&xattr->list);
 969                         }
 970                         goto out;
 971                 }
 972         }
 973         if (flags & XATTR_REPLACE) {
 974                 xattr = new_xattr;
 975                 err = -ENODATA;
 976         } else {
 977                 list_add(&new_xattr->list, &xattrs->head);
 978                 xattr = NULL;
 979         }
 980 out:
 981         spin_unlock(&xattrs->lock);
 982         if (xattr) {
 983                 kfree(xattr->name);
 984                 kfree(xattr);
 985         }
 986         return err;
 987
 988 }
 989
 990 static bool xattr_is_trusted(const char *name)
 991 {
 992         return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
 993 }
 994
 995 static int xattr_list_one(char **buffer, ssize_t *remaining_size,
 996                           const char *name)
 997 {
 998         size_t len = strlen(name) + 1;
 999         if (*buffer) {
1000                 if (*remaining_size < len)
1001                         return -ERANGE;
1002                 memcpy(*buffer, name, len);
1003                 *buffer += len;
1004         }
1005         *remaining_size -= len;
1006         return 0;
1007 }
1008
1009 /*
1010  * xattr LIST operation for in-memory/pseudo filesystems
1011  */
1012 ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs,
1013                           char *buffer, size_t size)
1014 {
1015         bool trusted = capable(CAP_SYS_ADMIN);
1016         struct simple_xattr *xattr;
1017         ssize_t remaining_size = size;
1018         int err = 0;
1019
1020 #ifdef CONFIG_FS_POSIX_ACL
1021         if (IS_POSIXACL(inode)) {
1022                 if (inode->i_acl) {
1023                         err = xattr_list_one(&buffer, &remaining_size,
1024                                              XATTR_NAME_POSIX_ACL_ACCESS);
1025                         if (err)
1026                                 return err;
1027                 }
1028                 if (inode->i_default_acl) {
1029                         err = xattr_list_one(&buffer, &remaining_size,
1030                                              XATTR_NAME_POSIX_ACL_DEFAULT);
1031                         if (err)
1032                                 return err;
1033                 }
1034         }
1035 #endif
1036
1037         spin_lock(&xattrs->lock);
1038         list_for_each_entry(xattr, &xattrs->head, list) {
1039                 /* skip "trusted." attributes for unprivileged callers */
1040                 if (!trusted && xattr_is_trusted(xattr->name))
1041                         continue;
1042
1043                 err = xattr_list_one(&buffer, &remaining_size, xattr->name);
1044                 if (err)
1045                         break;
1046         }
1047         spin_unlock(&xattrs->lock);
1048
1049         return err ? err : size - remaining_size;
1050 }
1051
1052 /*
1053  * Adds an extended attribute to the list
1054  */
1055 void simple_xattr_list_add(struct simple_xattrs *xattrs,
1056                            struct simple_xattr *new_xattr)
1057 {
1058         spin_lock(&xattrs->lock);
1059         list_add(&new_xattr->list, &xattrs->head);
1060         spin_unlock(&xattrs->lock);
1061 }