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