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 #include "internal.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 EXPORT_SYMBOL_GPL(__vfs_setxattr_noperm);
 207
 208
 209 int
 210 vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
 211                 size_t size, int flags)
 212 {
 213         struct inode *inode = dentry->d_inode;
 214         int error;
 215
 216         error = xattr_permission(inode, name, MAY_WRITE);
 217         if (error)
 218                 return error;
 219
 220         inode_lock(inode);
 221         error = security_inode_setxattr(dentry, name, value, size, flags);
 222         if (error)
 223                 goto out;
 224
 225         error = __vfs_setxattr_noperm(dentry, name, value, size, flags);
 226
 227 out:
 228         inode_unlock(inode);
 229         return error;
 230 }
 231 EXPORT_SYMBOL_GPL(vfs_setxattr);
 232
 233 ssize_t
 234 xattr_getsecurity(struct inode *inode, const char *name, void *value,
 235                         size_t size)
 236 {
 237         void *buffer = NULL;
 238         ssize_t len;
 239
 240         if (!value || !size) {
 241                 len = security_inode_getsecurity(inode, name, &buffer, false);
 242                 goto out_noalloc;
 243         }
 244
 245         len = security_inode_getsecurity(inode, name, &buffer, true);
 246         if (len < 0)
 247                 return len;
 248         if (size < len) {
 249                 len = -ERANGE;
 250                 goto out;
 251         }
 252         memcpy(value, buffer, len);
 253 out:
 254         kfree(buffer);
 255 out_noalloc:
 256         return len;
 257 }
 258 EXPORT_SYMBOL_GPL(xattr_getsecurity);
 259
 260 /*
 261  * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
 262  *
 263  * Allocate memory, if not already allocated, or re-allocate correct size,
 264  * before retrieving the extended attribute.
 265  *
 266  * Returns the result of alloc, if failed, or the getxattr operation.
 267  */
 268 ssize_t
 269 vfs_getxattr_alloc(struct dentry *dentry, const char *name, char **xattr_value,
 270                    size_t xattr_size, gfp_t flags)
 271 {
 272         const struct xattr_handler *handler;
 273         struct inode *inode = dentry->d_inode;
 274         char *value = *xattr_value;
 275         int error;
 276
 277         error = xattr_permission(inode, name, MAY_READ);
 278         if (error)
 279                 return error;
 280
 281         handler = xattr_resolve_name(inode, &name);
 282         if (IS_ERR(handler))
 283                 return PTR_ERR(handler);
 284         if (!handler->get)
 285                 return -EOPNOTSUPP;
 286         error = handler->get(handler, dentry, inode, name, NULL, 0);
 287         if (error < 0)
 288                 return error;
 289
 290         if (!value || (error > xattr_size)) {
 291                 value = krealloc(*xattr_value, error + 1, flags);
 292                 if (!value)
 293                         return -ENOMEM;
 294                 memset(value, 0, error + 1);
 295         }
 296
 297         error = handler->get(handler, dentry, inode, name, value, error);
 298         *xattr_value = value;
 299         return error;
 300 }
 301 EXPORT_SYMBOL_GPL(vfs_getxattr_alloc);
 302
 303 ssize_t
 304 __vfs_getxattr(struct dentry *dentry, struct inode *inode, const char *name,
 305                void *value, size_t size)
 306 {
 307         const struct xattr_handler *handler;
 308
 309         handler = xattr_resolve_name(inode, &name);
 310         if (IS_ERR(handler))
 311                 return PTR_ERR(handler);
 312         if (!handler->get)
 313                 return -EOPNOTSUPP;
 314         return handler->get(handler, dentry, inode, name, value, size);
 315 }
 316 EXPORT_SYMBOL(__vfs_getxattr);
 317
 318 ssize_t
 319 vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
 320 {
 321         struct inode *inode = dentry->d_inode;
 322         int error;
 323
 324         error = xattr_permission(inode, name, MAY_READ);
 325         if (error)
 326                 return error;
 327
 328         error = security_inode_getxattr(dentry, name);
 329         if (error)
 330                 return error;
 331
 332         if (!strncmp(name, XATTR_SECURITY_PREFIX,
 333                                 XATTR_SECURITY_PREFIX_LEN)) {
 334                 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
 335                 int ret = xattr_getsecurity(inode, suffix, value, size);
 336                 /*
 337                  * Only overwrite the return value if a security module
 338                  * is actually active.
 339                  */
 340                 if (ret == -EOPNOTSUPP)
 341                         goto nolsm;
 342                 return ret;
 343         }
 344 nolsm:
 345         return __vfs_getxattr(dentry, inode, name, value, size);
 346 }
 347 EXPORT_SYMBOL_GPL(vfs_getxattr);
 348
 349 ssize_t
 350 vfs_listxattr(struct dentry *dentry, char *list, size_t size)
 351 {
 352         struct inode *inode = d_inode(dentry);
 353         ssize_t error;
 354
 355         error = security_inode_listxattr(dentry);
 356         if (error)
 357                 return error;
 358         if (inode->i_op->listxattr && (inode->i_opflags & IOP_XATTR)) {
 359                 error = -EOPNOTSUPP;
 360                 error = inode->i_op->listxattr(dentry, list, size);
 361         } else {
 362                 error = security_inode_listsecurity(inode, list, size);
 363                 if (size && error > size)
 364                         error = -ERANGE;
 365         }
 366         return error;
 367 }
 368 EXPORT_SYMBOL_GPL(vfs_listxattr);
 369
 370 int
 371 __vfs_removexattr(struct dentry *dentry, const char *name)
 372 {
 373         struct inode *inode = d_inode(dentry);
 374         const struct xattr_handler *handler;
 375
 376         handler = xattr_resolve_name(inode, &name);
 377         if (IS_ERR(handler))
 378                 return PTR_ERR(handler);
 379         if (!handler->set)
 380                 return -EOPNOTSUPP;
 381         return handler->set(handler, dentry, inode, name, NULL, 0, XATTR_REPLACE);
 382 }
 383 EXPORT_SYMBOL(__vfs_removexattr);
 384
 385 /**
 386  *  __vfs_removexattr_noperm - perform removexattr operation without
 387  *  performing permission checks.
 388  *
 389  *  @dentry - object to perform setxattr on
 390  *  @name - xattr name to set
 391  *
 392  *  returns the result of the internal setxattr or setsecurity operations.
 393  *
 394  *  This function requires the caller to lock the inode's i_mutex before it
 395  *  is executed. It also assumes that the caller will make the appropriate
 396  *  permission checks.
 397  */
 398 int
 399 __vfs_removexattr_noperm(struct dentry *dentry, const char *name)
 400 {
 401         int error;
 402
 403         error =__vfs_removexattr(dentry, name);
 404         if (!error) {
 405                 fsnotify_xattr(dentry);
 406                 evm_inode_post_removexattr(dentry, name);
 407         }
 408         return error;
 409 }
 410 EXPORT_SYMBOL_GPL(__vfs_removexattr_noperm);
 411
 412 int
 413 vfs_removexattr(struct dentry *dentry, const char *name)
 414 {
 415         struct inode *inode = dentry->d_inode;
 416         int error;
 417
 418         error = xattr_permission(inode, name, MAY_WRITE);
 419         if (error)
 420                 return error;
 421
 422         inode_lock(inode);
 423         error = security_inode_removexattr(dentry, name);
 424         if (error)
 425                 goto out;
 426
 427         error = __vfs_removexattr_noperm(dentry, name);
 428
 429 out:
 430         inode_unlock(inode);
 431         return error;
 432 }
 433 EXPORT_SYMBOL_GPL(vfs_removexattr);
 434
 435
 436 /*
 437  * Extended attribute SET operations
 438  */
 439 static long
 440 setxattr(struct dentry *d, const char __user *name, const void __user *value,
 441          size_t size, int flags)
 442 {
 443         int error;
 444         void *kvalue = NULL;
 445         char kname[XATTR_NAME_MAX + 1];
 446
 447         if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
 448                 return -EINVAL;
 449
 450         error = strncpy_from_user(kname, name, sizeof(kname));
 451         if (error == 0 || error == sizeof(kname))
 452                 error = -ERANGE;
 453         if (error < 0)
 454                 return error;
 455
 456         if (size) {
 457                 if (size > XATTR_SIZE_MAX)
 458                         return -E2BIG;
 459                 kvalue = kvmalloc(size, GFP_KERNEL);
 460                 if (!kvalue)
 461                         return -ENOMEM;
 462                 if (copy_from_user(kvalue, value, size)) {
 463                         error = -EFAULT;
 464                         goto out;
 465                 }
 466                 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
 467                     (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
 468                         posix_acl_fix_xattr_from_user(kvalue, size);
 469                 else if (strcmp(kname, XATTR_NAME_CAPS) == 0) {
 470                         error = cap_convert_nscap(d, &kvalue, size);
 471                         if (error < 0)
 472                                 goto out;
 473                         size = error;
 474                 }
 475         }
 476
 477         error = vfs_setxattr(d, kname, kvalue, size, flags);
 478 out:
 479         kvfree(kvalue);
 480
 481         return error;
 482 }
 483
 484 static int path_setxattr(const char __user *pathname,
 485                          const char __user *name, const void __user *value,
 486                          size_t size, int flags, unsigned int lookup_flags)
 487 {
 488         struct path path;
 489         int error;
 490 retry:
 491         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 492         if (error)
 493                 return error;
 494         error = mnt_want_write(path.mnt);
 495         if (!error) {
 496                 error = setxattr(path.dentry, name, value, size, flags);
 497                 mnt_drop_write(path.mnt);
 498         }
 499         path_put(&path);
 500         if (retry_estale(error, lookup_flags)) {
 501                 lookup_flags |= LOOKUP_REVAL;
 502                 goto retry;
 503         }
 504         return error;
 505 }
 506
 507 SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
 508                 const char __user *, name, const void __user *, value,
 509                 size_t, size, int, flags)
 510 {
 511         return path_setxattr(pathname, name, value, size, flags, LOOKUP_FOLLOW);
 512 }
 513
 514 SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
 515                 const char __user *, name, const void __user *, value,
 516                 size_t, size, int, flags)
 517 {
 518         return path_setxattr(pathname, name, value, size, flags, 0);
 519 }
 520
 521 SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
 522                 const void __user *,value, size_t, size, int, flags)
 523 {
 524         struct fd f = fdget(fd);
 525         int error = -EBADF;
 526
 527         if (!f.file)
 528                 return error;
 529         audit_file(f.file);
 530         error = mnt_want_write_file_path(f.file);
 531         if (!error) {
 532                 error = setxattr(f.file->f_path.dentry, name, value, size, flags);
 533                 mnt_drop_write_file_path(f.file);
 534         }
 535         fdput(f);
 536         return error;
 537 }
 538
 539 /*
 540  * Extended attribute GET operations
 541  */
 542 static ssize_t
 543 getxattr(struct dentry *d, const char __user *name, void __user *value,
 544          size_t size)
 545 {
 546         ssize_t error;
 547         void *kvalue = NULL;
 548         char kname[XATTR_NAME_MAX + 1];
 549
 550         error = strncpy_from_user(kname, name, sizeof(kname));
 551         if (error == 0 || error == sizeof(kname))
 552                 error = -ERANGE;
 553         if (error < 0)
 554                 return error;
 555
 556         if (size) {
 557                 if (size > XATTR_SIZE_MAX)
 558                         size = XATTR_SIZE_MAX;
 559                 kvalue = kvzalloc(size, GFP_KERNEL);
 560                 if (!kvalue)
 561                         return -ENOMEM;
 562         }
 563
 564         error = vfs_getxattr(d, kname, kvalue, size);
 565         if (error > 0) {
 566                 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
 567                     (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
 568                         posix_acl_fix_xattr_to_user(kvalue, error);
 569                 if (size && copy_to_user(value, kvalue, error))
 570                         error = -EFAULT;
 571         } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
 572                 /* The file system tried to returned a value bigger
 573                    than XATTR_SIZE_MAX bytes. Not possible. */
 574                 error = -E2BIG;
 575         }
 576
 577         kvfree(kvalue);
 578
 579         return error;
 580 }
 581
 582 static ssize_t path_getxattr(const char __user *pathname,
 583                              const char __user *name, void __user *value,
 584                              size_t size, unsigned int lookup_flags)
 585 {
 586         struct path path;
 587         ssize_t error;
 588 retry:
 589         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 590         if (error)
 591                 return error;
 592         error = getxattr(path.dentry, name, value, size);
 593         path_put(&path);
 594         if (retry_estale(error, lookup_flags)) {
 595                 lookup_flags |= LOOKUP_REVAL;
 596                 goto retry;
 597         }
 598         return error;
 599 }
 600
 601 SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
 602                 const char __user *, name, void __user *, value, size_t, size)
 603 {
 604         return path_getxattr(pathname, name, value, size, LOOKUP_FOLLOW);
 605 }
 606
 607 SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
 608                 const char __user *, name, void __user *, value, size_t, size)
 609 {
 610         return path_getxattr(pathname, name, value, size, 0);
 611 }
 612
 613 SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
 614                 void __user *, value, size_t, size)
 615 {
 616         struct fd f = fdget(fd);
 617         ssize_t error = -EBADF;
 618
 619         if (!f.file)
 620                 return error;
 621         audit_file(f.file);
 622         error = getxattr(f.file->f_path.dentry, name, value, size);
 623         fdput(f);
 624         return error;
 625 }
 626
 627 /*
 628  * Extended attribute LIST operations
 629  */
 630 static ssize_t
 631 listxattr(struct dentry *d, char __user *list, size_t size)
 632 {
 633         ssize_t error;
 634         char *klist = NULL;
 635
 636         if (size) {
 637                 if (size > XATTR_LIST_MAX)
 638                         size = XATTR_LIST_MAX;
 639                 klist = kvmalloc(size, GFP_KERNEL);
 640                 if (!klist)
 641                         return -ENOMEM;
 642         }
 643
 644         error = vfs_listxattr(d, klist, size);
 645         if (error > 0) {
 646                 if (size && copy_to_user(list, klist, error))
 647                         error = -EFAULT;
 648         } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
 649                 /* The file system tried to returned a list bigger
 650                    than XATTR_LIST_MAX bytes. Not possible. */
 651                 error = -E2BIG;
 652         }
 653
 654         kvfree(klist);
 655
 656         return error;
 657 }
 658
 659 static ssize_t path_listxattr(const char __user *pathname, char __user *list,
 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 = listxattr(path.dentry, list, 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_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
 678                 size_t, size)
 679 {
 680         return path_listxattr(pathname, list, size, LOOKUP_FOLLOW);
 681 }
 682
 683 SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
 684                 size_t, size)
 685 {
 686         return path_listxattr(pathname, list, size, 0);
 687 }
 688
 689 SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
 690 {
 691         struct fd f = fdget(fd);
 692         ssize_t error = -EBADF;
 693
 694         if (!f.file)
 695                 return error;
 696         audit_file(f.file);
 697         error = listxattr(f.file->f_path.dentry, list, size);
 698         fdput(f);
 699         return error;
 700 }
 701
 702 /*
 703  * Extended attribute REMOVE operations
 704  */
 705 static long
 706 removexattr(struct dentry *d, const char __user *name)
 707 {
 708         int error;
 709         char kname[XATTR_NAME_MAX + 1];
 710
 711         error = strncpy_from_user(kname, name, sizeof(kname));
 712         if (error == 0 || error == sizeof(kname))
 713                 error = -ERANGE;
 714         if (error < 0)
 715                 return error;
 716
 717         return vfs_removexattr(d, kname);
 718 }
 719
 720 static int path_removexattr(const char __user *pathname,
 721                             const char __user *name, unsigned int lookup_flags)
 722 {
 723         struct path path;
 724         int error;
 725 retry:
 726         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 727         if (error)
 728                 return error;
 729         error = mnt_want_write(path.mnt);
 730         if (!error) {
 731                 error = removexattr(path.dentry, name);
 732                 mnt_drop_write(path.mnt);
 733         }
 734         path_put(&path);
 735         if (retry_estale(error, lookup_flags)) {
 736                 lookup_flags |= LOOKUP_REVAL;
 737                 goto retry;
 738         }
 739         return error;
 740 }
 741
 742 SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
 743                 const char __user *, name)
 744 {
 745         return path_removexattr(pathname, name, LOOKUP_FOLLOW);
 746 }
 747
 748 SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
 749                 const char __user *, name)
 750 {
 751         return path_removexattr(pathname, name, 0);
 752 }
 753
 754 SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
 755 {
 756         struct fd f = fdget(fd);
 757         int error = -EBADF;
 758
 759         if (!f.file)
 760                 return error;
 761         audit_file(f.file);
 762         error = mnt_want_write_file_path(f.file);
 763         if (!error) {
 764                 error = removexattr(f.file->f_path.dentry, name);
 765                 mnt_drop_write_file_path(f.file);
 766         }
 767         fdput(f);
 768         return error;
 769 }
 770
 771 /*
 772  * Combine the results of the list() operation from every xattr_handler in the
 773  * list.
 774  */
 775 ssize_t
 776 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 777 {
 778         const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
 779         unsigned int size = 0;
 780
 781         if (!buffer) {
 782                 for_each_xattr_handler(handlers, handler) {
 783                         if (!handler->name ||
 784                             (handler->list && !handler->list(dentry)))
 785                                 continue;
 786                         size += strlen(handler->name) + 1;
 787                 }
 788         } else {
 789                 char *buf = buffer;
 790                 size_t len;
 791
 792                 for_each_xattr_handler(handlers, handler) {
 793                         if (!handler->name ||
 794                             (handler->list && !handler->list(dentry)))
 795                                 continue;
 796                         len = strlen(handler->name);
 797                         if (len + 1 > buffer_size)
 798                                 return -ERANGE;
 799                         memcpy(buf, handler->name, len + 1);
 800                         buf += len + 1;
 801                         buffer_size -= len + 1;
 802                 }
 803                 size = buf - buffer;
 804         }
 805         return size;
 806 }
 807 EXPORT_SYMBOL(generic_listxattr);
 808
 809 /**
 810  * xattr_full_name  -  Compute full attribute name from suffix
 811  *
 812  * @handler:    handler of the xattr_handler operation
 813  * @name:       name passed to the xattr_handler operation
 814  *
 815  * The get and set xattr handler operations are called with the remainder of
 816  * the attribute name after skipping the handler's prefix: for example, "foo"
 817  * is passed to the get operation of a handler with prefix "user." to get
 818  * attribute "user.foo".  The full name is still "there" in the name though.
 819  *
 820  * Note: the list xattr handler operation when called from the vfs is passed a
 821  * NULL name; some file systems use this operation internally, with varying
 822  * semantics.
 823  */
 824 const char *xattr_full_name(const struct xattr_handler *handler,
 825                             const char *name)
 826 {
 827         size_t prefix_len = strlen(xattr_prefix(handler));
 828
 829         return name - prefix_len;
 830 }
 831 EXPORT_SYMBOL(xattr_full_name);
 832
 833 /*
 834  * Allocate new xattr and copy in the value; but leave the name to callers.
 835  */
 836 struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
 837 {
 838         struct simple_xattr *new_xattr;
 839         size_t len;
 840
 841         /* wrap around? */
 842         len = sizeof(*new_xattr) + size;
 843         if (len < sizeof(*new_xattr))
 844                 return NULL;
 845
 846         new_xattr = kmalloc(len, GFP_KERNEL);
 847         if (!new_xattr)
 848                 return NULL;
 849
 850         new_xattr->size = size;
 851         memcpy(new_xattr->value, value, size);
 852         return new_xattr;
 853 }
 854
 855 /*
 856  * xattr GET operation for in-memory/pseudo filesystems
 857  */
 858 int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
 859                      void *buffer, size_t size)
 860 {
 861         struct simple_xattr *xattr;
 862         int ret = -ENODATA;
 863
 864         spin_lock(&xattrs->lock);
 865         list_for_each_entry(xattr, &xattrs->head, list) {
 866                 if (strcmp(name, xattr->name))
 867                         continue;
 868
 869                 ret = xattr->size;
 870                 if (buffer) {
 871                         if (size < xattr->size)
 872                                 ret = -ERANGE;
 873                         else
 874                                 memcpy(buffer, xattr->value, xattr->size);
 875                 }
 876                 break;
 877         }
 878         spin_unlock(&xattrs->lock);
 879         return ret;
 880 }
 881
 882 /**
 883  * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
 884  * @xattrs: target simple_xattr list
 885  * @name: name of the extended attribute
 886  * @value: value of the xattr. If %NULL, will remove the attribute.
 887  * @size: size of the new xattr
 888  * @flags: %XATTR_{CREATE|REPLACE}
 889  *
 890  * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
 891  * with -EEXIST.  If %XATTR_REPLACE is set, the xattr should exist;
 892  * otherwise, fails with -ENODATA.
 893  *
 894  * Returns 0 on success, -errno on failure.
 895  */
 896 int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
 897                      const void *value, size_t size, int flags)
 898 {
 899         struct simple_xattr *xattr;
 900         struct simple_xattr *new_xattr = NULL;
 901         int err = 0;
 902
 903         /* value == NULL means remove */
 904         if (value) {
 905                 new_xattr = simple_xattr_alloc(value, size);
 906                 if (!new_xattr)
 907                         return -ENOMEM;
 908
 909                 new_xattr->name = kstrdup(name, GFP_KERNEL);
 910                 if (!new_xattr->name) {
 911                         kfree(new_xattr);
 912                         return -ENOMEM;
 913                 }
 914         }
 915
 916         spin_lock(&xattrs->lock);
 917         list_for_each_entry(xattr, &xattrs->head, list) {
 918                 if (!strcmp(name, xattr->name)) {
 919                         if (flags & XATTR_CREATE) {
 920                                 xattr = new_xattr;
 921                                 err = -EEXIST;
 922                         } else if (new_xattr) {
 923                                 list_replace(&xattr->list, &new_xattr->list);
 924                         } else {
 925                                 list_del(&xattr->list);
 926                         }
 927                         goto out;
 928                 }
 929         }
 930         if (flags & XATTR_REPLACE) {
 931                 xattr = new_xattr;
 932                 err = -ENODATA;
 933         } else {
 934                 list_add(&new_xattr->list, &xattrs->head);
 935                 xattr = NULL;
 936         }
 937 out:
 938         spin_unlock(&xattrs->lock);
 939         if (xattr) {
 940                 kfree(xattr->name);
 941                 kfree(xattr);
 942         }
 943         return err;
 944
 945 }
 946
 947 static bool xattr_is_trusted(const char *name)
 948 {
 949         return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
 950 }
 951
 952 static int xattr_list_one(char **buffer, ssize_t *remaining_size,
 953                           const char *name)
 954 {
 955         size_t len = strlen(name) + 1;
 956         if (*buffer) {
 957                 if (*remaining_size < len)
 958                         return -ERANGE;
 959                 memcpy(*buffer, name, len);
 960                 *buffer += len;
 961         }
 962         *remaining_size -= len;
 963         return 0;
 964 }
 965
 966 /*
 967  * xattr LIST operation for in-memory/pseudo filesystems
 968  */
 969 ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs,
 970                           char *buffer, size_t size)
 971 {
 972         bool trusted = capable(CAP_SYS_ADMIN);
 973         struct simple_xattr *xattr;
 974         ssize_t remaining_size = size;
 975         int err = 0;
 976
 977 #ifdef CONFIG_FS_POSIX_ACL
 978         if (inode->i_acl) {
 979                 err = xattr_list_one(&buffer, &remaining_size,
 980                                      XATTR_NAME_POSIX_ACL_ACCESS);
 981                 if (err)
 982                         return err;
 983         }
 984         if (inode->i_default_acl) {
 985                 err = xattr_list_one(&buffer, &remaining_size,
 986                                      XATTR_NAME_POSIX_ACL_DEFAULT);
 987                 if (err)
 988                         return err;
 989         }
 990 #endif
 991
 992         spin_lock(&xattrs->lock);
 993         list_for_each_entry(xattr, &xattrs->head, list) {
 994                 /* skip "trusted." attributes for unprivileged callers */
 995                 if (!trusted && xattr_is_trusted(xattr->name))
 996                         continue;
 997
 998                 err = xattr_list_one(&buffer, &remaining_size, xattr->name);
 999                 if (err)
1000                         break;
1001         }
1002         spin_unlock(&xattrs->lock);
1003
1004         return err ? err : size - remaining_size;
1005 }
1006
1007 /*
1008  * Adds an extended attribute to the list
1009  */
1010 void simple_xattr_list_add(struct simple_xattrs *xattrs,
1011                            struct simple_xattr *new_xattr)
1012 {
1013         spin_lock(&xattrs->lock);
1014         list_add(&new_xattr->list, &xattrs->head);
1015         spin_unlock(&xattrs->lock);
1016 }