fs/xattr.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3   File: fs/xattr.c
   4
   5   Extended attribute handling.
   6
   7   Copyright (C) 2001 by Andreas Gruenbacher <a.gruenbacher@computer.org>
   8   Copyright (C) 2001 SGI - Silicon Graphics, Inc <linux-xfs@oss.sgi.com>
   9   Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
  10  */
  11 #include <linux/fs.h>
  12 #include <linux/slab.h>
  13 #include <linux/file.h>
  14 #include <linux/xattr.h>
  15 #include <linux/mount.h>
  16 #include <linux/namei.h>
  17 #include <linux/security.h>
  18 #include <linux/evm.h>
  19 #include <linux/syscalls.h>
  20 #include <linux/export.h>
  21 #include <linux/fsnotify.h>
  22 #include <linux/audit.h>
  23 #include <linux/vmalloc.h>
  24 #include <linux/posix_acl_xattr.h>
  25
  26 #include <linux/uaccess.h>
  27
  28 static const char *
  29 strcmp_prefix(const char *a, const char *a_prefix)
  30 {
  31         while (*a_prefix && *a == *a_prefix) {
  32                 a++;
  33                 a_prefix++;
  34         }
  35         return *a_prefix ? NULL : a;
  36 }
  37
  38 /*
  39  * In order to implement different sets of xattr operations for each xattr
  40  * prefix, a filesystem should create a null-terminated array of struct
  41  * xattr_handler (one for each prefix) and hang a pointer to it off of the
  42  * s_xattr field of the superblock.
  43  */
  44 #define for_each_xattr_handler(handlers, handler)               \
  45         if (handlers)                                           \
  46                 for ((handler) = *(handlers)++;                 \
  47                         (handler) != NULL;                      \
  48                         (handler) = *(handlers)++)
  49
  50 /*
  51  * Find the xattr_handler with the matching prefix.
  52  */
  53 static const struct xattr_handler *
  54 xattr_resolve_name(struct inode *inode, const char **name)
  55 {
  56         const struct xattr_handler **handlers = inode->i_sb->s_xattr;
  57         const struct xattr_handler *handler;
  58
  59         if (!(inode->i_opflags & IOP_XATTR)) {
  60                 if (unlikely(is_bad_inode(inode)))
  61                         return ERR_PTR(-EIO);
  62                 return ERR_PTR(-EOPNOTSUPP);
  63         }
  64         for_each_xattr_handler(handlers, handler) {
  65                 const char *n;
  66
  67                 n = strcmp_prefix(*name, xattr_prefix(handler));
  68                 if (n) {
  69                         if (!handler->prefix ^ !*n) {
  70                                 if (*n)
  71                                         continue;
  72                                 return ERR_PTR(-EINVAL);
  73                         }
  74                         *name = n;
  75                         return handler;
  76                 }
  77         }
  78         return ERR_PTR(-EOPNOTSUPP);
  79 }
  80
  81 /*
  82  * Check permissions for extended attribute access.  This is a bit complicated
  83  * because different namespaces have very different rules.
  84  */
  85 static int
  86 xattr_permission(struct user_namespace *mnt_userns, struct inode *inode,
  87                  const char *name, int mask)
  88 {
  89         /*
  90          * We can never set or remove an extended attribute on a read-only
  91          * filesystem  or on an immutable / append-only inode.
  92          */
  93         if (mask & MAY_WRITE) {
  94                 if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
  95                         return -EPERM;
  96                 /*
  97                  * Updating an xattr will likely cause i_uid and i_gid
  98                  * to be writen back improperly if their true value is
  99                  * unknown to the vfs.
 100                  */
 101                 if (HAS_UNMAPPED_ID(inode))
 102                         return -EPERM;
 103         }
 104
 105         /*
 106          * No restriction for security.* and system.* from the VFS.  Decision
 107          * on these is left to the underlying filesystem / security module.
 108          */
 109         if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||
 110             !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
 111                 return 0;
 112
 113         /*
 114          * The trusted.* namespace can only be accessed by privileged users.
 115          */
 116         if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
 117                 if (!capable(CAP_SYS_ADMIN))
 118                         return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
 119                 return 0;
 120         }
 121
 122         /*
 123          * In the user.* namespace, only regular files and directories can have
 124          * extended attributes. For sticky directories, only the owner and
 125          * privileged users can write attributes.
 126          */
 127         if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
 128                 if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
 129                         return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
 130                 if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&
 131                     (mask & MAY_WRITE) &&
 132                     !inode_owner_or_capable(mnt_userns, inode))
 133                         return -EPERM;
 134         }
 135
 136         return inode_permission(mnt_userns, inode, mask);
 137 }
 138
 139 /*
 140  * Look for any handler that deals with the specified namespace.
 141  */
 142 int
 143 xattr_supported_namespace(struct inode *inode, const char *prefix)
 144 {
 145         const struct xattr_handler **handlers = inode->i_sb->s_xattr;
 146         const struct xattr_handler *handler;
 147         size_t preflen;
 148
 149         if (!(inode->i_opflags & IOP_XATTR)) {
 150                 if (unlikely(is_bad_inode(inode)))
 151                         return -EIO;
 152                 return -EOPNOTSUPP;
 153         }
 154
 155         preflen = strlen(prefix);
 156
 157         for_each_xattr_handler(handlers, handler) {
 158                 if (!strncmp(xattr_prefix(handler), prefix, preflen))
 159                         return 0;
 160         }
 161
 162         return -EOPNOTSUPP;
 163 }
 164 EXPORT_SYMBOL(xattr_supported_namespace);
 165
 166 int
 167 __vfs_setxattr(struct user_namespace *mnt_userns, struct dentry *dentry,
 168                struct inode *inode, const char *name, const void *value,
 169                size_t size, int flags)
 170 {
 171         const struct xattr_handler *handler;
 172
 173         handler = xattr_resolve_name(inode, &name);
 174         if (IS_ERR(handler))
 175                 return PTR_ERR(handler);
 176         if (!handler->set)
 177                 return -EOPNOTSUPP;
 178         if (size == 0)
 179                 value = "";  /* empty EA, do not remove */
 180         return handler->set(handler, mnt_userns, dentry, inode, name, value,
 181                             size, flags);
 182 }
 183 EXPORT_SYMBOL(__vfs_setxattr);
 184
 185 /**
 186  *  __vfs_setxattr_noperm - perform setxattr operation without performing
 187  *  permission checks.
 188  *
 189  *  @mnt_userns - user namespace of the mount the inode was found from
 190  *  @dentry - object to perform setxattr on
 191  *  @name - xattr name to set
 192  *  @value - value to set @name to
 193  *  @size - size of @value
 194  *  @flags - flags to pass into filesystem operations
 195  *
 196  *  returns the result of the internal setxattr or setsecurity operations.
 197  *
 198  *  This function requires the caller to lock the inode's i_mutex before it
 199  *  is executed. It also assumes that the caller will make the appropriate
 200  *  permission checks.
 201  */
 202 int __vfs_setxattr_noperm(struct user_namespace *mnt_userns,
 203                           struct dentry *dentry, const char *name,
 204                           const void *value, size_t size, int flags)
 205 {
 206         struct inode *inode = dentry->d_inode;
 207         int error = -EAGAIN;
 208         int issec = !strncmp(name, XATTR_SECURITY_PREFIX,
 209                                    XATTR_SECURITY_PREFIX_LEN);
 210
 211         if (issec)
 212                 inode->i_flags &= ~S_NOSEC;
 213         if (inode->i_opflags & IOP_XATTR) {
 214                 error = __vfs_setxattr(mnt_userns, dentry, inode, name, value,
 215                                        size, flags);
 216                 if (!error) {
 217                         fsnotify_xattr(dentry);
 218                         security_inode_post_setxattr(dentry, name, value,
 219                                                      size, flags);
 220                 }
 221         } else {
 222                 if (unlikely(is_bad_inode(inode)))
 223                         return -EIO;
 224         }
 225         if (error == -EAGAIN) {
 226                 error = -EOPNOTSUPP;
 227
 228                 if (issec) {
 229                         const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
 230
 231                         error = security_inode_setsecurity(inode, suffix, value,
 232                                                            size, flags);
 233                         if (!error)
 234                                 fsnotify_xattr(dentry);
 235                 }
 236         }
 237
 238         return error;
 239 }
 240
 241 /**
 242  * __vfs_setxattr_locked - set an extended attribute while holding the inode
 243  * lock
 244  *
 245  *  @dentry: object to perform setxattr on
 246  *  @name: xattr name to set
 247  *  @value: value to set @name to
 248  *  @size: size of @value
 249  *  @flags: flags to pass into filesystem operations
 250  *  @delegated_inode: on return, will contain an inode pointer that
 251  *  a delegation was broken on, NULL if none.
 252  */
 253 int
 254 __vfs_setxattr_locked(struct user_namespace *mnt_userns, struct dentry *dentry,
 255                       const char *name, const void *value, size_t size,
 256                       int flags, struct inode **delegated_inode)
 257 {
 258         struct inode *inode = dentry->d_inode;
 259         int error;
 260
 261         error = xattr_permission(mnt_userns, inode, name, MAY_WRITE);
 262         if (error)
 263                 return error;
 264
 265         error = security_inode_setxattr(mnt_userns, dentry, name, value, size,
 266                                         flags);
 267         if (error)
 268                 goto out;
 269
 270         error = try_break_deleg(inode, delegated_inode);
 271         if (error)
 272                 goto out;
 273
 274         error = __vfs_setxattr_noperm(mnt_userns, dentry, name, value,
 275                                       size, flags);
 276
 277 out:
 278         return error;
 279 }
 280 EXPORT_SYMBOL_GPL(__vfs_setxattr_locked);
 281
 282 int
 283 vfs_setxattr(struct user_namespace *mnt_userns, struct dentry *dentry,
 284              const char *name, const void *value, size_t size, int flags)
 285 {
 286         struct inode *inode = dentry->d_inode;
 287         struct inode *delegated_inode = NULL;
 288         const void  *orig_value = value;
 289         int error;
 290
 291         if (size && strcmp(name, XATTR_NAME_CAPS) == 0) {
 292                 error = cap_convert_nscap(mnt_userns, dentry, &value, size);
 293                 if (error < 0)
 294                         return error;
 295                 size = error;
 296         }
 297
 298 retry_deleg:
 299         inode_lock(inode);
 300         error = __vfs_setxattr_locked(mnt_userns, dentry, name, value, size,
 301                                       flags, &delegated_inode);
 302         inode_unlock(inode);
 303
 304         if (delegated_inode) {
 305                 error = break_deleg_wait(&delegated_inode);
 306                 if (!error)
 307                         goto retry_deleg;
 308         }
 309         if (value != orig_value)
 310                 kfree(value);
 311
 312         return error;
 313 }
 314 EXPORT_SYMBOL_GPL(vfs_setxattr);
 315
 316 static ssize_t
 317 xattr_getsecurity(struct user_namespace *mnt_userns, struct inode *inode,
 318                   const char *name, void *value, size_t size)
 319 {
 320         void *buffer = NULL;
 321         ssize_t len;
 322
 323         if (!value || !size) {
 324                 len = security_inode_getsecurity(mnt_userns, inode, name,
 325                                                  &buffer, false);
 326                 goto out_noalloc;
 327         }
 328
 329         len = security_inode_getsecurity(mnt_userns, inode, name, &buffer,
 330                                          true);
 331         if (len < 0)
 332                 return len;
 333         if (size < len) {
 334                 len = -ERANGE;
 335                 goto out;
 336         }
 337         memcpy(value, buffer, len);
 338 out:
 339         kfree(buffer);
 340 out_noalloc:
 341         return len;
 342 }
 343
 344 /*
 345  * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
 346  *
 347  * Allocate memory, if not already allocated, or re-allocate correct size,
 348  * before retrieving the extended attribute.
 349  *
 350  * Returns the result of alloc, if failed, or the getxattr operation.
 351  */
 352 ssize_t
 353 vfs_getxattr_alloc(struct user_namespace *mnt_userns, struct dentry *dentry,
 354                    const char *name, char **xattr_value, size_t xattr_size,
 355                    gfp_t flags)
 356 {
 357         const struct xattr_handler *handler;
 358         struct inode *inode = dentry->d_inode;
 359         char *value = *xattr_value;
 360         int error;
 361
 362         error = xattr_permission(mnt_userns, inode, name, MAY_READ);
 363         if (error)
 364                 return error;
 365
 366         handler = xattr_resolve_name(inode, &name);
 367         if (IS_ERR(handler))
 368                 return PTR_ERR(handler);
 369         if (!handler->get)
 370                 return -EOPNOTSUPP;
 371         error = handler->get(handler, dentry, inode, name, NULL, 0);
 372         if (error < 0)
 373                 return error;
 374
 375         if (!value || (error > xattr_size)) {
 376                 value = krealloc(*xattr_value, error + 1, flags);
 377                 if (!value)
 378                         return -ENOMEM;
 379                 memset(value, 0, error + 1);
 380         }
 381
 382         error = handler->get(handler, dentry, inode, name, value, error);
 383         *xattr_value = value;
 384         return error;
 385 }
 386
 387 ssize_t
 388 __vfs_getxattr(struct dentry *dentry, struct inode *inode, const char *name,
 389                void *value, size_t size)
 390 {
 391         const struct xattr_handler *handler;
 392
 393         handler = xattr_resolve_name(inode, &name);
 394         if (IS_ERR(handler))
 395                 return PTR_ERR(handler);
 396         if (!handler->get)
 397                 return -EOPNOTSUPP;
 398         return handler->get(handler, dentry, inode, name, value, size);
 399 }
 400 EXPORT_SYMBOL(__vfs_getxattr);
 401
 402 ssize_t
 403 vfs_getxattr(struct user_namespace *mnt_userns, struct dentry *dentry,
 404              const char *name, void *value, size_t size)
 405 {
 406         struct inode *inode = dentry->d_inode;
 407         int error;
 408
 409         error = xattr_permission(mnt_userns, inode, name, MAY_READ);
 410         if (error)
 411                 return error;
 412
 413         error = security_inode_getxattr(dentry, name);
 414         if (error)
 415                 return error;
 416
 417         if (!strncmp(name, XATTR_SECURITY_PREFIX,
 418                                 XATTR_SECURITY_PREFIX_LEN)) {
 419                 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
 420                 int ret = xattr_getsecurity(mnt_userns, inode, suffix, value,
 421                                             size);
 422                 /*
 423                  * Only overwrite the return value if a security module
 424                  * is actually active.
 425                  */
 426                 if (ret == -EOPNOTSUPP)
 427                         goto nolsm;
 428                 return ret;
 429         }
 430 nolsm:
 431         return __vfs_getxattr(dentry, inode, name, value, size);
 432 }
 433 EXPORT_SYMBOL_GPL(vfs_getxattr);
 434
 435 ssize_t
 436 vfs_listxattr(struct dentry *dentry, char *list, size_t size)
 437 {
 438         struct inode *inode = d_inode(dentry);
 439         ssize_t error;
 440
 441         error = security_inode_listxattr(dentry);
 442         if (error)
 443                 return error;
 444         if (inode->i_op->listxattr && (inode->i_opflags & IOP_XATTR)) {
 445                 error = inode->i_op->listxattr(dentry, list, size);
 446         } else {
 447                 error = security_inode_listsecurity(inode, list, size);
 448                 if (size && error > size)
 449                         error = -ERANGE;
 450         }
 451         return error;
 452 }
 453 EXPORT_SYMBOL_GPL(vfs_listxattr);
 454
 455 int
 456 __vfs_removexattr(struct user_namespace *mnt_userns, struct dentry *dentry,
 457                   const char *name)
 458 {
 459         struct inode *inode = d_inode(dentry);
 460         const struct xattr_handler *handler;
 461
 462         handler = xattr_resolve_name(inode, &name);
 463         if (IS_ERR(handler))
 464                 return PTR_ERR(handler);
 465         if (!handler->set)
 466                 return -EOPNOTSUPP;
 467         return handler->set(handler, mnt_userns, dentry, inode, name, NULL, 0,
 468                             XATTR_REPLACE);
 469 }
 470 EXPORT_SYMBOL(__vfs_removexattr);
 471
 472 /**
 473  * __vfs_removexattr_locked - set an extended attribute while holding the inode
 474  * lock
 475  *
 476  *  @dentry: object to perform setxattr on
 477  *  @name: name of xattr to remove
 478  *  @delegated_inode: on return, will contain an inode pointer that
 479  *  a delegation was broken on, NULL if none.
 480  */
 481 int
 482 __vfs_removexattr_locked(struct user_namespace *mnt_userns,
 483                          struct dentry *dentry, const char *name,
 484                          struct inode **delegated_inode)
 485 {
 486         struct inode *inode = dentry->d_inode;
 487         int error;
 488
 489         error = xattr_permission(mnt_userns, inode, name, MAY_WRITE);
 490         if (error)
 491                 return error;
 492
 493         error = security_inode_removexattr(mnt_userns, dentry, name);
 494         if (error)
 495                 goto out;
 496
 497         error = try_break_deleg(inode, delegated_inode);
 498         if (error)
 499                 goto out;
 500
 501         error = __vfs_removexattr(mnt_userns, dentry, name);
 502
 503         if (!error) {
 504                 fsnotify_xattr(dentry);
 505                 evm_inode_post_removexattr(dentry, name);
 506         }
 507
 508 out:
 509         return error;
 510 }
 511 EXPORT_SYMBOL_GPL(__vfs_removexattr_locked);
 512
 513 int
 514 vfs_removexattr(struct user_namespace *mnt_userns, struct dentry *dentry,
 515                 const char *name)
 516 {
 517         struct inode *inode = dentry->d_inode;
 518         struct inode *delegated_inode = NULL;
 519         int error;
 520
 521 retry_deleg:
 522         inode_lock(inode);
 523         error = __vfs_removexattr_locked(mnt_userns, dentry,
 524                                          name, &delegated_inode);
 525         inode_unlock(inode);
 526
 527         if (delegated_inode) {
 528                 error = break_deleg_wait(&delegated_inode);
 529                 if (!error)
 530                         goto retry_deleg;
 531         }
 532
 533         return error;
 534 }
 535 EXPORT_SYMBOL_GPL(vfs_removexattr);
 536
 537 /*
 538  * Extended attribute SET operations
 539  */
 540 static long
 541 setxattr(struct user_namespace *mnt_userns, struct dentry *d,
 542          const char __user *name, const void __user *value, size_t size,
 543          int flags)
 544 {
 545         int error;
 546         void *kvalue = NULL;
 547         char kname[XATTR_NAME_MAX + 1];
 548
 549         if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
 550                 return -EINVAL;
 551
 552         error = strncpy_from_user(kname, name, sizeof(kname));
 553         if (error == 0 || error == sizeof(kname))
 554                 error = -ERANGE;
 555         if (error < 0)
 556                 return error;
 557
 558         if (size) {
 559                 if (size > XATTR_SIZE_MAX)
 560                         return -E2BIG;
 561                 kvalue = kvmalloc(size, GFP_KERNEL);
 562                 if (!kvalue)
 563                         return -ENOMEM;
 564                 if (copy_from_user(kvalue, value, size)) {
 565                         error = -EFAULT;
 566                         goto out;
 567                 }
 568                 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
 569                     (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
 570                         posix_acl_fix_xattr_from_user(mnt_userns, kvalue, size);
 571         }
 572
 573         error = vfs_setxattr(mnt_userns, d, kname, kvalue, size, flags);
 574 out:
 575         kvfree(kvalue);
 576
 577         return error;
 578 }
 579
 580 static int path_setxattr(const char __user *pathname,
 581                          const char __user *name, const void __user *value,
 582                          size_t size, int flags, unsigned int lookup_flags)
 583 {
 584         struct path path;
 585         int error;
 586
 587 retry:
 588         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 589         if (error)
 590                 return error;
 591         error = mnt_want_write(path.mnt);
 592         if (!error) {
 593                 error = setxattr(mnt_user_ns(path.mnt), path.dentry, name,
 594                                  value, size, flags);
 595                 mnt_drop_write(path.mnt);
 596         }
 597         path_put(&path);
 598         if (retry_estale(error, lookup_flags)) {
 599                 lookup_flags |= LOOKUP_REVAL;
 600                 goto retry;
 601         }
 602         return error;
 603 }
 604
 605 SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
 606                 const char __user *, name, const void __user *, value,
 607                 size_t, size, int, flags)
 608 {
 609         return path_setxattr(pathname, name, value, size, flags, LOOKUP_FOLLOW);
 610 }
 611
 612 SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
 613                 const char __user *, name, const void __user *, value,
 614                 size_t, size, int, flags)
 615 {
 616         return path_setxattr(pathname, name, value, size, flags, 0);
 617 }
 618
 619 SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
 620                 const void __user *,value, size_t, size, int, flags)
 621 {
 622         struct fd f = fdget(fd);
 623         int error = -EBADF;
 624
 625         if (!f.file)
 626                 return error;
 627         audit_file(f.file);
 628         error = mnt_want_write_file(f.file);
 629         if (!error) {
 630                 error = setxattr(file_mnt_user_ns(f.file),
 631                                  f.file->f_path.dentry, name,
 632                                  value, size, flags);
 633                 mnt_drop_write_file(f.file);
 634         }
 635         fdput(f);
 636         return error;
 637 }
 638
 639 /*
 640  * Extended attribute GET operations
 641  */
 642 static ssize_t
 643 getxattr(struct user_namespace *mnt_userns, struct dentry *d,
 644          const char __user *name, void __user *value, size_t size)
 645 {
 646         ssize_t error;
 647         void *kvalue = NULL;
 648         char kname[XATTR_NAME_MAX + 1];
 649
 650         error = strncpy_from_user(kname, name, sizeof(kname));
 651         if (error == 0 || error == sizeof(kname))
 652                 error = -ERANGE;
 653         if (error < 0)
 654                 return error;
 655
 656         if (size) {
 657                 if (size > XATTR_SIZE_MAX)
 658                         size = XATTR_SIZE_MAX;
 659                 kvalue = kvzalloc(size, GFP_KERNEL);
 660                 if (!kvalue)
 661                         return -ENOMEM;
 662         }
 663
 664         error = vfs_getxattr(mnt_userns, d, kname, kvalue, size);
 665         if (error > 0) {
 666                 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
 667                     (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
 668                         posix_acl_fix_xattr_to_user(mnt_userns, kvalue, error);
 669                 if (size && copy_to_user(value, kvalue, error))
 670                         error = -EFAULT;
 671         } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
 672                 /* The file system tried to returned a value bigger
 673                    than XATTR_SIZE_MAX bytes. Not possible. */
 674                 error = -E2BIG;
 675         }
 676
 677         kvfree(kvalue);
 678
 679         return error;
 680 }
 681
 682 static ssize_t path_getxattr(const char __user *pathname,
 683                              const char __user *name, void __user *value,
 684                              size_t size, unsigned int lookup_flags)
 685 {
 686         struct path path;
 687         ssize_t error;
 688 retry:
 689         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 690         if (error)
 691                 return error;
 692         error = getxattr(mnt_user_ns(path.mnt), path.dentry, name, value, size);
 693         path_put(&path);
 694         if (retry_estale(error, lookup_flags)) {
 695                 lookup_flags |= LOOKUP_REVAL;
 696                 goto retry;
 697         }
 698         return error;
 699 }
 700
 701 SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
 702                 const char __user *, name, void __user *, value, size_t, size)
 703 {
 704         return path_getxattr(pathname, name, value, size, LOOKUP_FOLLOW);
 705 }
 706
 707 SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
 708                 const char __user *, name, void __user *, value, size_t, size)
 709 {
 710         return path_getxattr(pathname, name, value, size, 0);
 711 }
 712
 713 SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
 714                 void __user *, value, size_t, size)
 715 {
 716         struct fd f = fdget(fd);
 717         ssize_t error = -EBADF;
 718
 719         if (!f.file)
 720                 return error;
 721         audit_file(f.file);
 722         error = getxattr(file_mnt_user_ns(f.file), f.file->f_path.dentry,
 723                          name, value, size);
 724         fdput(f);
 725         return error;
 726 }
 727
 728 /*
 729  * Extended attribute LIST operations
 730  */
 731 static ssize_t
 732 listxattr(struct dentry *d, char __user *list, size_t size)
 733 {
 734         ssize_t error;
 735         char *klist = NULL;
 736
 737         if (size) {
 738                 if (size > XATTR_LIST_MAX)
 739                         size = XATTR_LIST_MAX;
 740                 klist = kvmalloc(size, GFP_KERNEL);
 741                 if (!klist)
 742                         return -ENOMEM;
 743         }
 744
 745         error = vfs_listxattr(d, klist, size);
 746         if (error > 0) {
 747                 if (size && copy_to_user(list, klist, error))
 748                         error = -EFAULT;
 749         } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
 750                 /* The file system tried to returned a list bigger
 751                    than XATTR_LIST_MAX bytes. Not possible. */
 752                 error = -E2BIG;
 753         }
 754
 755         kvfree(klist);
 756
 757         return error;
 758 }
 759
 760 static ssize_t path_listxattr(const char __user *pathname, char __user *list,
 761                               size_t size, unsigned int lookup_flags)
 762 {
 763         struct path path;
 764         ssize_t error;
 765 retry:
 766         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 767         if (error)
 768                 return error;
 769         error = listxattr(path.dentry, list, size);
 770         path_put(&path);
 771         if (retry_estale(error, lookup_flags)) {
 772                 lookup_flags |= LOOKUP_REVAL;
 773                 goto retry;
 774         }
 775         return error;
 776 }
 777
 778 SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
 779                 size_t, size)
 780 {
 781         return path_listxattr(pathname, list, size, LOOKUP_FOLLOW);
 782 }
 783
 784 SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
 785                 size_t, size)
 786 {
 787         return path_listxattr(pathname, list, size, 0);
 788 }
 789
 790 SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
 791 {
 792         struct fd f = fdget(fd);
 793         ssize_t error = -EBADF;
 794
 795         if (!f.file)
 796                 return error;
 797         audit_file(f.file);
 798         error = listxattr(f.file->f_path.dentry, list, size);
 799         fdput(f);
 800         return error;
 801 }
 802
 803 /*
 804  * Extended attribute REMOVE operations
 805  */
 806 static long
 807 removexattr(struct user_namespace *mnt_userns, struct dentry *d,
 808             const char __user *name)
 809 {
 810         int error;
 811         char kname[XATTR_NAME_MAX + 1];
 812
 813         error = strncpy_from_user(kname, name, sizeof(kname));
 814         if (error == 0 || error == sizeof(kname))
 815                 error = -ERANGE;
 816         if (error < 0)
 817                 return error;
 818
 819         return vfs_removexattr(mnt_userns, d, kname);
 820 }
 821
 822 static int path_removexattr(const char __user *pathname,
 823                             const char __user *name, unsigned int lookup_flags)
 824 {
 825         struct path path;
 826         int error;
 827 retry:
 828         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 829         if (error)
 830                 return error;
 831         error = mnt_want_write(path.mnt);
 832         if (!error) {
 833                 error = removexattr(mnt_user_ns(path.mnt), path.dentry, name);
 834                 mnt_drop_write(path.mnt);
 835         }
 836         path_put(&path);
 837         if (retry_estale(error, lookup_flags)) {
 838                 lookup_flags |= LOOKUP_REVAL;
 839                 goto retry;
 840         }
 841         return error;
 842 }
 843
 844 SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
 845                 const char __user *, name)
 846 {
 847         return path_removexattr(pathname, name, LOOKUP_FOLLOW);
 848 }
 849
 850 SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
 851                 const char __user *, name)
 852 {
 853         return path_removexattr(pathname, name, 0);
 854 }
 855
 856 SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
 857 {
 858         struct fd f = fdget(fd);
 859         int error = -EBADF;
 860
 861         if (!f.file)
 862                 return error;
 863         audit_file(f.file);
 864         error = mnt_want_write_file(f.file);
 865         if (!error) {
 866                 error = removexattr(file_mnt_user_ns(f.file),
 867                                     f.file->f_path.dentry, name);
 868                 mnt_drop_write_file(f.file);
 869         }
 870         fdput(f);
 871         return error;
 872 }
 873
 874 /*
 875  * Combine the results of the list() operation from every xattr_handler in the
 876  * list.
 877  */
 878 ssize_t
 879 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 880 {
 881         const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
 882         unsigned int size = 0;
 883
 884         if (!buffer) {
 885                 for_each_xattr_handler(handlers, handler) {
 886                         if (!handler->name ||
 887                             (handler->list && !handler->list(dentry)))
 888                                 continue;
 889                         size += strlen(handler->name) + 1;
 890                 }
 891         } else {
 892                 char *buf = buffer;
 893                 size_t len;
 894
 895                 for_each_xattr_handler(handlers, handler) {
 896                         if (!handler->name ||
 897                             (handler->list && !handler->list(dentry)))
 898                                 continue;
 899                         len = strlen(handler->name);
 900                         if (len + 1 > buffer_size)
 901                                 return -ERANGE;
 902                         memcpy(buf, handler->name, len + 1);
 903                         buf += len + 1;
 904                         buffer_size -= len + 1;
 905                 }
 906                 size = buf - buffer;
 907         }
 908         return size;
 909 }
 910 EXPORT_SYMBOL(generic_listxattr);
 911
 912 /**
 913  * xattr_full_name  -  Compute full attribute name from suffix
 914  *
 915  * @handler:    handler of the xattr_handler operation
 916  * @name:       name passed to the xattr_handler operation
 917  *
 918  * The get and set xattr handler operations are called with the remainder of
 919  * the attribute name after skipping the handler's prefix: for example, "foo"
 920  * is passed to the get operation of a handler with prefix "user." to get
 921  * attribute "user.foo".  The full name is still "there" in the name though.
 922  *
 923  * Note: the list xattr handler operation when called from the vfs is passed a
 924  * NULL name; some file systems use this operation internally, with varying
 925  * semantics.
 926  */
 927 const char *xattr_full_name(const struct xattr_handler *handler,
 928                             const char *name)
 929 {
 930         size_t prefix_len = strlen(xattr_prefix(handler));
 931
 932         return name - prefix_len;
 933 }
 934 EXPORT_SYMBOL(xattr_full_name);
 935
 936 /*
 937  * Allocate new xattr and copy in the value; but leave the name to callers.
 938  */
 939 struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
 940 {
 941         struct simple_xattr *new_xattr;
 942         size_t len;
 943
 944         /* wrap around? */
 945         len = sizeof(*new_xattr) + size;
 946         if (len < sizeof(*new_xattr))
 947                 return NULL;
 948
 949         new_xattr = kvmalloc(len, GFP_KERNEL);
 950         if (!new_xattr)
 951                 return NULL;
 952
 953         new_xattr->size = size;
 954         memcpy(new_xattr->value, value, size);
 955         return new_xattr;
 956 }
 957
 958 /*
 959  * xattr GET operation for in-memory/pseudo filesystems
 960  */
 961 int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
 962                      void *buffer, size_t size)
 963 {
 964         struct simple_xattr *xattr;
 965         int ret = -ENODATA;
 966
 967         spin_lock(&xattrs->lock);
 968         list_for_each_entry(xattr, &xattrs->head, list) {
 969                 if (strcmp(name, xattr->name))
 970                         continue;
 971
 972                 ret = xattr->size;
 973                 if (buffer) {
 974                         if (size < xattr->size)
 975                                 ret = -ERANGE;
 976                         else
 977                                 memcpy(buffer, xattr->value, xattr->size);
 978                 }
 979                 break;
 980         }
 981         spin_unlock(&xattrs->lock);
 982         return ret;
 983 }
 984
 985 /**
 986  * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
 987  * @xattrs: target simple_xattr list
 988  * @name: name of the extended attribute
 989  * @value: value of the xattr. If %NULL, will remove the attribute.
 990  * @size: size of the new xattr
 991  * @flags: %XATTR_{CREATE|REPLACE}
 992  * @removed_size: returns size of the removed xattr, -1 if none removed
 993  *
 994  * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
 995  * with -EEXIST.  If %XATTR_REPLACE is set, the xattr should exist;
 996  * otherwise, fails with -ENODATA.
 997  *
 998  * Returns 0 on success, -errno on failure.
 999  */
1000 int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
1001                      const void *value, size_t size, int flags,
1002                      ssize_t *removed_size)
1003 {
1004         struct simple_xattr *xattr;
1005         struct simple_xattr *new_xattr = NULL;
1006         int err = 0;
1007
1008         if (removed_size)
1009                 *removed_size = -1;
1010
1011         /* value == NULL means remove */
1012         if (value) {
1013                 new_xattr = simple_xattr_alloc(value, size);
1014                 if (!new_xattr)
1015                         return -ENOMEM;
1016
1017                 new_xattr->name = kstrdup(name, GFP_KERNEL);
1018                 if (!new_xattr->name) {
1019                         kvfree(new_xattr);
1020                         return -ENOMEM;
1021                 }
1022         }
1023
1024         spin_lock(&xattrs->lock);
1025         list_for_each_entry(xattr, &xattrs->head, list) {
1026                 if (!strcmp(name, xattr->name)) {
1027                         if (flags & XATTR_CREATE) {
1028                                 xattr = new_xattr;
1029                                 err = -EEXIST;
1030                         } else if (new_xattr) {
1031                                 list_replace(&xattr->list, &new_xattr->list);
1032                                 if (removed_size)
1033                                         *removed_size = xattr->size;
1034                         } else {
1035                                 list_del(&xattr->list);
1036                                 if (removed_size)
1037                                         *removed_size = xattr->size;
1038                         }
1039                         goto out;
1040                 }
1041         }
1042         if (flags & XATTR_REPLACE) {
1043                 xattr = new_xattr;
1044                 err = -ENODATA;
1045         } else {
1046                 list_add(&new_xattr->list, &xattrs->head);
1047                 xattr = NULL;
1048         }
1049 out:
1050         spin_unlock(&xattrs->lock);
1051         if (xattr) {
1052                 kfree(xattr->name);
1053                 kvfree(xattr);
1054         }
1055         return err;
1056
1057 }
1058
1059 static bool xattr_is_trusted(const char *name)
1060 {
1061         return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
1062 }
1063
1064 static int xattr_list_one(char **buffer, ssize_t *remaining_size,
1065                           const char *name)
1066 {
1067         size_t len = strlen(name) + 1;
1068         if (*buffer) {
1069                 if (*remaining_size < len)
1070                         return -ERANGE;
1071                 memcpy(*buffer, name, len);
1072                 *buffer += len;
1073         }
1074         *remaining_size -= len;
1075         return 0;
1076 }
1077
1078 /*
1079  * xattr LIST operation for in-memory/pseudo filesystems
1080  */
1081 ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs,
1082                           char *buffer, size_t size)
1083 {
1084         bool trusted = capable(CAP_SYS_ADMIN);
1085         struct simple_xattr *xattr;
1086         ssize_t remaining_size = size;
1087         int err = 0;
1088
1089 #ifdef CONFIG_FS_POSIX_ACL
1090         if (IS_POSIXACL(inode)) {
1091                 if (inode->i_acl) {
1092                         err = xattr_list_one(&buffer, &remaining_size,
1093                                              XATTR_NAME_POSIX_ACL_ACCESS);
1094                         if (err)
1095                                 return err;
1096                 }
1097                 if (inode->i_default_acl) {
1098                         err = xattr_list_one(&buffer, &remaining_size,
1099                                              XATTR_NAME_POSIX_ACL_DEFAULT);
1100                         if (err)
1101                                 return err;
1102                 }
1103         }
1104 #endif
1105
1106         spin_lock(&xattrs->lock);
1107         list_for_each_entry(xattr, &xattrs->head, list) {
1108                 /* skip "trusted." attributes for unprivileged callers */
1109                 if (!trusted && xattr_is_trusted(xattr->name))
1110                         continue;
1111
1112                 err = xattr_list_one(&buffer, &remaining_size, xattr->name);
1113                 if (err)
1114                         break;
1115         }
1116         spin_unlock(&xattrs->lock);
1117
1118         return err ? err : size - remaining_size;
1119 }
1120
1121 /*
1122  * Adds an extended attribute to the list
1123  */
1124 void simple_xattr_list_add(struct simple_xattrs *xattrs,
1125                            struct simple_xattr *new_xattr)
1126 {
1127         spin_lock(&xattrs->lock);
1128         list_add(&new_xattr->list, &xattrs->head);
1129         spin_unlock(&xattrs->lock);
1130 }