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