fs/btrfs/xattr.c

   1 /*
   2  * Copyright (C) 2007 Red Hat.  All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public
   6  * License v2 as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public
  14  * License along with this program; if not, write to the
  15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  16  * Boston, MA 021110-1307, USA.
  17  */
  18
  19 #include <linux/init.h>
  20 #include <linux/fs.h>
  21 #include <linux/slab.h>
  22 #include <linux/rwsem.h>
  23 #include <linux/xattr.h>
  24 #include <linux/security.h>
  25 #include <linux/posix_acl_xattr.h>
  26 #include "ctree.h"
  27 #include "btrfs_inode.h"
  28 #include "transaction.h"
  29 #include "xattr.h"
  30 #include "disk-io.h"
  31 #include "props.h"
  32 #include "locking.h"
  33
  34
  35 ssize_t __btrfs_getxattr(struct inode *inode, const char *name,
  36                                 void *buffer, size_t size)
  37 {
  38         struct btrfs_dir_item *di;
  39         struct btrfs_root *root = BTRFS_I(inode)->root;
  40         struct btrfs_path *path;
  41         struct extent_buffer *leaf;
  42         int ret = 0;
  43         unsigned long data_ptr;
  44
  45         path = btrfs_alloc_path();
  46         if (!path)
  47                 return -ENOMEM;
  48
  49         /* lookup the xattr by name */
  50         di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(inode), name,
  51                                 strlen(name), 0);
  52         if (!di) {
  53                 ret = -ENODATA;
  54                 goto out;
  55         } else if (IS_ERR(di)) {
  56                 ret = PTR_ERR(di);
  57                 goto out;
  58         }
  59
  60         leaf = path->nodes[0];
  61         /* if size is 0, that means we want the size of the attr */
  62         if (!size) {
  63                 ret = btrfs_dir_data_len(leaf, di);
  64                 goto out;
  65         }
  66
  67         /* now get the data out of our dir_item */
  68         if (btrfs_dir_data_len(leaf, di) > size) {
  69                 ret = -ERANGE;
  70                 goto out;
  71         }
  72
  73         /*
  74          * The way things are packed into the leaf is like this
  75          * |struct btrfs_dir_item|name|data|
  76          * where name is the xattr name, so security.foo, and data is the
  77          * content of the xattr.  data_ptr points to the location in memory
  78          * where the data starts in the in memory leaf
  79          */
  80         data_ptr = (unsigned long)((char *)(di + 1) +
  81                                    btrfs_dir_name_len(leaf, di));
  82         read_extent_buffer(leaf, buffer, data_ptr,
  83                            btrfs_dir_data_len(leaf, di));
  84         ret = btrfs_dir_data_len(leaf, di);
  85
  86 out:
  87         btrfs_free_path(path);
  88         return ret;
  89 }
  90
  91 static int do_setxattr(struct btrfs_trans_handle *trans,
  92                        struct inode *inode, const char *name,
  93                        const void *value, size_t size, int flags)
  94 {
  95         struct btrfs_dir_item *di = NULL;
  96         struct btrfs_root *root = BTRFS_I(inode)->root;
  97         struct btrfs_path *path;
  98         size_t name_len = strlen(name);
  99         int ret = 0;
 100
 101         if (name_len + size > BTRFS_MAX_XATTR_SIZE(root))
 102                 return -ENOSPC;
 103
 104         path = btrfs_alloc_path();
 105         if (!path)
 106                 return -ENOMEM;
 107         path->skip_release_on_error = 1;
 108
 109         if (!value) {
 110                 di = btrfs_lookup_xattr(trans, root, path, btrfs_ino(inode),
 111                                         name, name_len, -1);
 112                 if (!di && (flags & XATTR_REPLACE))
 113                         ret = -ENODATA;
 114                 else if (di)
 115                         ret = btrfs_delete_one_dir_name(trans, root, path, di);
 116                 goto out;
 117         }
 118
 119         /*
 120          * For a replace we can't just do the insert blindly.
 121          * Do a lookup first (read-only btrfs_search_slot), and return if xattr
 122          * doesn't exist. If it exists, fall down below to the insert/replace
 123          * path - we can't race with a concurrent xattr delete, because the VFS
 124          * locks the inode's i_mutex before calling setxattr or removexattr.
 125          */
 126         if (flags & XATTR_REPLACE) {
 127                 ASSERT(mutex_is_locked(&inode->i_mutex));
 128                 di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(inode),
 129                                         name, name_len, 0);
 130                 if (!di) {
 131                         ret = -ENODATA;
 132                         goto out;
 133                 }
 134                 btrfs_release_path(path);
 135                 di = NULL;
 136         }
 137
 138         ret = btrfs_insert_xattr_item(trans, root, path, btrfs_ino(inode),
 139                                       name, name_len, value, size);
 140         if (ret == -EOVERFLOW) {
 141                 /*
 142                  * We have an existing item in a leaf, split_leaf couldn't
 143                  * expand it. That item might have or not a dir_item that
 144                  * matches our target xattr, so lets check.
 145                  */
 146                 ret = 0;
 147                 btrfs_assert_tree_locked(path->nodes[0]);
 148                 di = btrfs_match_dir_item_name(root, path, name, name_len);
 149                 if (!di && !(flags & XATTR_REPLACE)) {
 150                         ret = -ENOSPC;
 151                         goto out;
 152                 }
 153         } else if (ret == -EEXIST) {
 154                 ret = 0;
 155                 di = btrfs_match_dir_item_name(root, path, name, name_len);
 156                 ASSERT(di); /* logic error */
 157         } else if (ret) {
 158                 goto out;
 159         }
 160
 161         if (di && (flags & XATTR_CREATE)) {
 162                 ret = -EEXIST;
 163                 goto out;
 164         }
 165
 166         if (di) {
 167                 /*
 168                  * We're doing a replace, and it must be atomic, that is, at
 169                  * any point in time we have either the old or the new xattr
 170                  * value in the tree. We don't want readers (getxattr and
 171                  * listxattrs) to miss a value, this is specially important
 172                  * for ACLs.
 173                  */
 174                 const int slot = path->slots[0];
 175                 struct extent_buffer *leaf = path->nodes[0];
 176                 const u16 old_data_len = btrfs_dir_data_len(leaf, di);
 177                 const u32 item_size = btrfs_item_size_nr(leaf, slot);
 178                 const u32 data_size = sizeof(*di) + name_len + size;
 179                 struct btrfs_item *item;
 180                 unsigned long data_ptr;
 181                 char *ptr;
 182
 183                 if (size > old_data_len) {
 184                         if (btrfs_leaf_free_space(root, leaf) <
 185                             (size - old_data_len)) {
 186                                 ret = -ENOSPC;
 187                                 goto out;
 188                         }
 189                 }
 190
 191                 if (old_data_len + name_len + sizeof(*di) == item_size) {
 192                         /* No other xattrs packed in the same leaf item. */
 193                         if (size > old_data_len)
 194                                 btrfs_extend_item(root, path,
 195                                                   size - old_data_len);
 196                         else if (size < old_data_len)
 197                                 btrfs_truncate_item(root, path, data_size, 1);
 198                 } else {
 199                         /* There are other xattrs packed in the same item. */
 200                         ret = btrfs_delete_one_dir_name(trans, root, path, di);
 201                         if (ret)
 202                                 goto out;
 203                         btrfs_extend_item(root, path, data_size);
 204                 }
 205
 206                 item = btrfs_item_nr(slot);
 207                 ptr = btrfs_item_ptr(leaf, slot, char);
 208                 ptr += btrfs_item_size(leaf, item) - data_size;
 209                 di = (struct btrfs_dir_item *)ptr;
 210                 btrfs_set_dir_data_len(leaf, di, size);
 211                 data_ptr = ((unsigned long)(di + 1)) + name_len;
 212                 write_extent_buffer(leaf, value, data_ptr, size);
 213                 btrfs_mark_buffer_dirty(leaf);
 214         } else {
 215                 /*
 216                  * Insert, and we had space for the xattr, so path->slots[0] is
 217                  * where our xattr dir_item is and btrfs_insert_xattr_item()
 218                  * filled it.
 219                  */
 220         }
 221 out:
 222         btrfs_free_path(path);
 223         return ret;
 224 }
 225
 226 /*
 227  * @value: "" makes the attribute to empty, NULL removes it
 228  */
 229 int __btrfs_setxattr(struct btrfs_trans_handle *trans,
 230                      struct inode *inode, const char *name,
 231                      const void *value, size_t size, int flags)
 232 {
 233         struct btrfs_root *root = BTRFS_I(inode)->root;
 234         int ret;
 235
 236         if (trans)
 237                 return do_setxattr(trans, inode, name, value, size, flags);
 238
 239         trans = btrfs_start_transaction(root, 2);
 240         if (IS_ERR(trans))
 241                 return PTR_ERR(trans);
 242
 243         ret = do_setxattr(trans, inode, name, value, size, flags);
 244         if (ret)
 245                 goto out;
 246
 247         inode_inc_iversion(inode);
 248         inode->i_ctime = CURRENT_TIME;
 249         set_bit(BTRFS_INODE_COPY_EVERYTHING, &BTRFS_I(inode)->runtime_flags);
 250         ret = btrfs_update_inode(trans, root, inode);
 251         BUG_ON(ret);
 252 out:
 253         btrfs_end_transaction(trans, root);
 254         return ret;
 255 }
 256
 257 ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
 258 {
 259         struct btrfs_key key, found_key;
 260         struct inode *inode = dentry->d_inode;
 261         struct btrfs_root *root = BTRFS_I(inode)->root;
 262         struct btrfs_path *path;
 263         struct extent_buffer *leaf;
 264         struct btrfs_dir_item *di;
 265         int ret = 0, slot;
 266         size_t total_size = 0, size_left = size;
 267         unsigned long name_ptr;
 268         size_t name_len;
 269
 270         /*
 271          * ok we want all objects associated with this id.
 272          * NOTE: we set key.offset = 0; because we want to start with the
 273          * first xattr that we find and walk forward
 274          */
 275         key.objectid = btrfs_ino(inode);
 276         btrfs_set_key_type(&key, BTRFS_XATTR_ITEM_KEY);
 277         key.offset = 0;
 278
 279         path = btrfs_alloc_path();
 280         if (!path)
 281                 return -ENOMEM;
 282         path->reada = 2;
 283
 284         /* search for our xattrs */
 285         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 286         if (ret < 0)
 287                 goto err;
 288
 289         while (1) {
 290                 leaf = path->nodes[0];
 291                 slot = path->slots[0];
 292
 293                 /* this is where we start walking through the path */
 294                 if (slot >= btrfs_header_nritems(leaf)) {
 295                         /*
 296                          * if we've reached the last slot in this leaf we need
 297                          * to go to the next leaf and reset everything
 298                          */
 299                         ret = btrfs_next_leaf(root, path);
 300                         if (ret < 0)
 301                                 goto err;
 302                         else if (ret > 0)
 303                                 break;
 304                         continue;
 305                 }
 306
 307                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
 308
 309                 /* check to make sure this item is what we want */
 310                 if (found_key.objectid != key.objectid)
 311                         break;
 312                 if (found_key.type > BTRFS_XATTR_ITEM_KEY)
 313                         break;
 314                 if (found_key.type < BTRFS_XATTR_ITEM_KEY)
 315                         goto next;
 316
 317                 di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
 318                 if (verify_dir_item(root, leaf, di))
 319                         goto next;
 320
 321                 name_len = btrfs_dir_name_len(leaf, di);
 322                 total_size += name_len + 1;
 323
 324                 /* we are just looking for how big our buffer needs to be */
 325                 if (!size)
 326                         goto next;
 327
 328                 if (!buffer || (name_len + 1) > size_left) {
 329                         ret = -ERANGE;
 330                         goto err;
 331                 }
 332
 333                 name_ptr = (unsigned long)(di + 1);
 334                 read_extent_buffer(leaf, buffer, name_ptr, name_len);
 335                 buffer[name_len] = '\0';
 336
 337                 size_left -= name_len + 1;
 338                 buffer += name_len + 1;
 339 next:
 340                 path->slots[0]++;
 341         }
 342         ret = total_size;
 343
 344 err:
 345         btrfs_free_path(path);
 346
 347         return ret;
 348 }
 349
 350 /*
 351  * List of handlers for synthetic system.* attributes.  All real ondisk
 352  * attributes are handled directly.
 353  */
 354 const struct xattr_handler *btrfs_xattr_handlers[] = {
 355 #ifdef CONFIG_BTRFS_FS_POSIX_ACL
 356         &posix_acl_access_xattr_handler,
 357         &posix_acl_default_xattr_handler,
 358 #endif
 359         NULL,
 360 };
 361
 362 /*
 363  * Check if the attribute is in a supported namespace.
 364  *
 365  * This is applied after the check for the synthetic attributes in the system
 366  * namespace.
 367  */
 368 static int btrfs_is_valid_xattr(const char *name)
 369 {
 370         int len = strlen(name);
 371         int prefixlen = 0;
 372
 373         if (!strncmp(name, XATTR_SECURITY_PREFIX,
 374                         XATTR_SECURITY_PREFIX_LEN))
 375                 prefixlen = XATTR_SECURITY_PREFIX_LEN;
 376         else if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
 377                 prefixlen = XATTR_SYSTEM_PREFIX_LEN;
 378         else if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN))
 379                 prefixlen = XATTR_TRUSTED_PREFIX_LEN;
 380         else if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN))
 381                 prefixlen = XATTR_USER_PREFIX_LEN;
 382         else if (!strncmp(name, XATTR_BTRFS_PREFIX, XATTR_BTRFS_PREFIX_LEN))
 383                 prefixlen = XATTR_BTRFS_PREFIX_LEN;
 384         else
 385                 return -EOPNOTSUPP;
 386
 387         /*
 388          * The name cannot consist of just prefix
 389          */
 390         if (len <= prefixlen)
 391                 return -EINVAL;
 392
 393         return 0;
 394 }
 395
 396 ssize_t btrfs_getxattr(struct dentry *dentry, const char *name,
 397                        void *buffer, size_t size)
 398 {
 399         int ret;
 400
 401         /*
 402          * If this is a request for a synthetic attribute in the system.*
 403          * namespace use the generic infrastructure to resolve a handler
 404          * for it via sb->s_xattr.
 405          */
 406         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
 407                 return generic_getxattr(dentry, name, buffer, size);
 408
 409         ret = btrfs_is_valid_xattr(name);
 410         if (ret)
 411                 return ret;
 412         return __btrfs_getxattr(dentry->d_inode, name, buffer, size);
 413 }
 414
 415 int btrfs_setxattr(struct dentry *dentry, const char *name, const void *value,
 416                    size_t size, int flags)
 417 {
 418         struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
 419         int ret;
 420
 421         /*
 422          * The permission on security.* and system.* is not checked
 423          * in permission().
 424          */
 425         if (btrfs_root_readonly(root))
 426                 return -EROFS;
 427
 428         /*
 429          * If this is a request for a synthetic attribute in the system.*
 430          * namespace use the generic infrastructure to resolve a handler
 431          * for it via sb->s_xattr.
 432          */
 433         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
 434                 return generic_setxattr(dentry, name, value, size, flags);
 435
 436         ret = btrfs_is_valid_xattr(name);
 437         if (ret)
 438                 return ret;
 439
 440         if (!strncmp(name, XATTR_BTRFS_PREFIX, XATTR_BTRFS_PREFIX_LEN))
 441                 return btrfs_set_prop(dentry->d_inode, name,
 442                                       value, size, flags);
 443
 444         if (size == 0)
 445                 value = "";  /* empty EA, do not remove */
 446
 447         return __btrfs_setxattr(NULL, dentry->d_inode, name, value, size,
 448                                 flags);
 449 }
 450
 451 int btrfs_removexattr(struct dentry *dentry, const char *name)
 452 {
 453         struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
 454         int ret;
 455
 456         /*
 457          * The permission on security.* and system.* is not checked
 458          * in permission().
 459          */
 460         if (btrfs_root_readonly(root))
 461                 return -EROFS;
 462
 463         /*
 464          * If this is a request for a synthetic attribute in the system.*
 465          * namespace use the generic infrastructure to resolve a handler
 466          * for it via sb->s_xattr.
 467          */
 468         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
 469                 return generic_removexattr(dentry, name);
 470
 471         ret = btrfs_is_valid_xattr(name);
 472         if (ret)
 473                 return ret;
 474
 475         if (!strncmp(name, XATTR_BTRFS_PREFIX, XATTR_BTRFS_PREFIX_LEN))
 476                 return btrfs_set_prop(dentry->d_inode, name,
 477                                       NULL, 0, XATTR_REPLACE);
 478
 479         return __btrfs_setxattr(NULL, dentry->d_inode, name, NULL, 0,
 480                                 XATTR_REPLACE);
 481 }
 482
 483 static int btrfs_initxattrs(struct inode *inode,
 484                             const struct xattr *xattr_array, void *fs_info)
 485 {
 486         const struct xattr *xattr;
 487         struct btrfs_trans_handle *trans = fs_info;
 488         char *name;
 489         int err = 0;
 490
 491         for (xattr = xattr_array; xattr->name != NULL; xattr++) {
 492                 name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
 493                                strlen(xattr->name) + 1, GFP_NOFS);
 494                 if (!name) {
 495                         err = -ENOMEM;
 496                         break;
 497                 }
 498                 strcpy(name, XATTR_SECURITY_PREFIX);
 499                 strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
 500                 err = __btrfs_setxattr(trans, inode, name,
 501                                        xattr->value, xattr->value_len, 0);
 502                 kfree(name);
 503                 if (err < 0)
 504                         break;
 505         }
 506         return err;
 507 }
 508
 509 int btrfs_xattr_security_init(struct btrfs_trans_handle *trans,
 510                               struct inode *inode, struct inode *dir,
 511                               const struct qstr *qstr)
 512 {
 513         return security_inode_init_security(inode, dir, qstr,
 514                                             &btrfs_initxattrs, trans);
 515 }