fs/xattr.c

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