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