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 (IS_ERR(di))
 115                         ret = PTR_ERR(di);
 116                 else if (di)
 117                         ret = btrfs_delete_one_dir_name(trans, root, path, di);
 118                 goto out;
 119         }
 120
 121         /*
 122          * For a replace we can't just do the insert blindly.
 123          * Do a lookup first (read-only btrfs_search_slot), and return if xattr
 124          * doesn't exist. If it exists, fall down below to the insert/replace
 125          * path - we can't race with a concurrent xattr delete, because the VFS
 126          * locks the inode's i_mutex before calling setxattr or removexattr.
 127          */
 128         if (flags & XATTR_REPLACE) {
 129                 ASSERT(mutex_is_locked(&inode->i_mutex));
 130                 di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(inode),
 131                                         name, name_len, 0);
 132                 if (!di)
 133                         ret = -ENODATA;
 134                 else if (IS_ERR(di))
 135                         ret = PTR_ERR(di);
 136                 if (ret)
 137                         goto out;
 138                 btrfs_release_path(path);
 139                 di = NULL;
 140         }
 141
 142         ret = btrfs_insert_xattr_item(trans, root, path, btrfs_ino(inode),
 143                                       name, name_len, value, size);
 144         if (ret == -EOVERFLOW) {
 145                 /*
 146                  * We have an existing item in a leaf, split_leaf couldn't
 147                  * expand it. That item might have or not a dir_item that
 148                  * matches our target xattr, so lets check.
 149                  */
 150                 ret = 0;
 151                 btrfs_assert_tree_locked(path->nodes[0]);
 152                 di = btrfs_match_dir_item_name(root, path, name, name_len);
 153                 if (!di && !(flags & XATTR_REPLACE)) {
 154                         ret = -ENOSPC;
 155                         goto out;
 156                 }
 157         } else if (ret == -EEXIST) {
 158                 ret = 0;
 159                 di = btrfs_match_dir_item_name(root, path, name, name_len);
 160                 ASSERT(di); /* logic error */
 161         } else if (ret) {
 162                 goto out;
 163         }
 164
 165         if (di && (flags & XATTR_CREATE)) {
 166                 ret = -EEXIST;
 167                 goto out;
 168         }
 169
 170         if (di) {
 171                 /*
 172                  * We're doing a replace, and it must be atomic, that is, at
 173                  * any point in time we have either the old or the new xattr
 174                  * value in the tree. We don't want readers (getxattr and
 175                  * listxattrs) to miss a value, this is specially important
 176                  * for ACLs.
 177                  */
 178                 const int slot = path->slots[0];
 179                 struct extent_buffer *leaf = path->nodes[0];
 180                 const u16 old_data_len = btrfs_dir_data_len(leaf, di);
 181                 const u32 item_size = btrfs_item_size_nr(leaf, slot);
 182                 const u32 data_size = sizeof(*di) + name_len + size;
 183                 struct btrfs_item *item;
 184                 unsigned long data_ptr;
 185                 char *ptr;
 186
 187                 if (size > old_data_len) {
 188                         if (btrfs_leaf_free_space(root, leaf) <
 189                             (size - old_data_len)) {
 190                                 ret = -ENOSPC;
 191                                 goto out;
 192                         }
 193                 }
 194
 195                 if (old_data_len + name_len + sizeof(*di) == item_size) {
 196                         /* No other xattrs packed in the same leaf item. */
 197                         if (size > old_data_len)
 198                                 btrfs_extend_item(root, path,
 199                                                   size - old_data_len);
 200                         else if (size < old_data_len)
 201                                 btrfs_truncate_item(root, path, data_size, 1);
 202                 } else {
 203                         /* There are other xattrs packed in the same item. */
 204                         ret = btrfs_delete_one_dir_name(trans, root, path, di);
 205                         if (ret)
 206                                 goto out;
 207                         btrfs_extend_item(root, path, data_size);
 208                 }
 209
 210                 item = btrfs_item_nr(slot);
 211                 ptr = btrfs_item_ptr(leaf, slot, char);
 212                 ptr += btrfs_item_size(leaf, item) - data_size;
 213                 di = (struct btrfs_dir_item *)ptr;
 214                 btrfs_set_dir_data_len(leaf, di, size);
 215                 data_ptr = ((unsigned long)(di + 1)) + name_len;
 216                 write_extent_buffer(leaf, value, data_ptr, size);
 217                 btrfs_mark_buffer_dirty(leaf);
 218         } else {
 219                 /*
 220                  * Insert, and we had space for the xattr, so path->slots[0] is
 221                  * where our xattr dir_item is and btrfs_insert_xattr_item()
 222                  * filled it.
 223                  */
 224         }
 225 out:
 226         btrfs_free_path(path);
 227         return ret;
 228 }
 229
 230 /*
 231  * @value: "" makes the attribute to empty, NULL removes it
 232  */
 233 int __btrfs_setxattr(struct btrfs_trans_handle *trans,
 234                      struct inode *inode, const char *name,
 235                      const void *value, size_t size, int flags)
 236 {
 237         struct btrfs_root *root = BTRFS_I(inode)->root;
 238         int ret;
 239
 240         if (trans)
 241                 return do_setxattr(trans, inode, name, value, size, flags);
 242
 243         trans = btrfs_start_transaction(root, 2);
 244         if (IS_ERR(trans))
 245                 return PTR_ERR(trans);
 246
 247         ret = do_setxattr(trans, inode, name, value, size, flags);
 248         if (ret)
 249                 goto out;
 250
 251         inode_inc_iversion(inode);
 252         inode->i_ctime = CURRENT_TIME;
 253         set_bit(BTRFS_INODE_COPY_EVERYTHING, &BTRFS_I(inode)->runtime_flags);
 254         ret = btrfs_update_inode(trans, root, inode);
 255         BUG_ON(ret);
 256 out:
 257         btrfs_end_transaction(trans, root);
 258         return ret;
 259 }
 260
 261 ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
 262 {
 263         struct btrfs_key key, found_key;
 264         struct inode *inode = d_inode(dentry);
 265         struct btrfs_root *root = BTRFS_I(inode)->root;
 266         struct btrfs_path *path;
 267         struct extent_buffer *leaf;
 268         struct btrfs_dir_item *di;
 269         int ret = 0, slot;
 270         size_t total_size = 0, size_left = size;
 271         unsigned long name_ptr;
 272         size_t name_len;
 273
 274         /*
 275          * ok we want all objects associated with this id.
 276          * NOTE: we set key.offset = 0; because we want to start with the
 277          * first xattr that we find and walk forward
 278          */
 279         key.objectid = btrfs_ino(inode);
 280         key.type = BTRFS_XATTR_ITEM_KEY;
 281         key.offset = 0;
 282
 283         path = btrfs_alloc_path();
 284         if (!path)
 285                 return -ENOMEM;
 286         path->reada = 2;
 287
 288         /* search for our xattrs */
 289         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 290         if (ret < 0)
 291                 goto err;
 292
 293         while (1) {
 294                 leaf = path->nodes[0];
 295                 slot = path->slots[0];
 296
 297                 /* this is where we start walking through the path */
 298                 if (slot >= btrfs_header_nritems(leaf)) {
 299                         /*
 300                          * if we've reached the last slot in this leaf we need
 301                          * to go to the next leaf and reset everything
 302                          */
 303                         ret = btrfs_next_leaf(root, path);
 304                         if (ret < 0)
 305                                 goto err;
 306                         else if (ret > 0)
 307                                 break;
 308                         continue;
 309                 }
 310
 311                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
 312
 313                 /* check to make sure this item is what we want */
 314                 if (found_key.objectid != key.objectid)
 315                         break;
 316                 if (found_key.type > BTRFS_XATTR_ITEM_KEY)
 317                         break;
 318                 if (found_key.type < BTRFS_XATTR_ITEM_KEY)
 319                         goto next;
 320
 321                 di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
 322                 if (verify_dir_item(root, leaf, di))
 323                         goto next;
 324
 325                 name_len = btrfs_dir_name_len(leaf, di);
 326                 total_size += name_len + 1;
 327
 328                 /* we are just looking for how big our buffer needs to be */
 329                 if (!size)
 330                         goto next;
 331
 332                 if (!buffer || (name_len + 1) > size_left) {
 333                         ret = -ERANGE;
 334                         goto err;
 335                 }
 336
 337                 name_ptr = (unsigned long)(di + 1);
 338                 read_extent_buffer(leaf, buffer, name_ptr, name_len);
 339                 buffer[name_len] = '\0';
 340
 341                 size_left -= name_len + 1;
 342                 buffer += name_len + 1;
 343 next:
 344                 path->slots[0]++;
 345         }
 346         ret = total_size;
 347
 348 err:
 349         btrfs_free_path(path);
 350
 351         return ret;
 352 }
 353
 354 /*
 355  * List of handlers for synthetic system.* attributes.  All real ondisk
 356  * attributes are handled directly.
 357  */
 358 const struct xattr_handler *btrfs_xattr_handlers[] = {
 359 #ifdef CONFIG_BTRFS_FS_POSIX_ACL
 360         &posix_acl_access_xattr_handler,
 361         &posix_acl_default_xattr_handler,
 362 #endif
 363         NULL,
 364 };
 365
 366 /*
 367  * Check if the attribute is in a supported namespace.
 368  *
 369  * This is applied after the check for the synthetic attributes in the system
 370  * namespace.
 371  */
 372 static int btrfs_is_valid_xattr(const char *name)
 373 {
 374         int len = strlen(name);
 375         int prefixlen = 0;
 376
 377         if (!strncmp(name, XATTR_SECURITY_PREFIX,
 378                         XATTR_SECURITY_PREFIX_LEN))
 379                 prefixlen = XATTR_SECURITY_PREFIX_LEN;
 380         else if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
 381                 prefixlen = XATTR_SYSTEM_PREFIX_LEN;
 382         else if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN))
 383                 prefixlen = XATTR_TRUSTED_PREFIX_LEN;
 384         else if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN))
 385                 prefixlen = XATTR_USER_PREFIX_LEN;
 386         else if (!strncmp(name, XATTR_BTRFS_PREFIX, XATTR_BTRFS_PREFIX_LEN))
 387                 prefixlen = XATTR_BTRFS_PREFIX_LEN;
 388         else
 389                 return -EOPNOTSUPP;
 390
 391         /*
 392          * The name cannot consist of just prefix
 393          */
 394         if (len <= prefixlen)
 395                 return -EINVAL;
 396
 397         return 0;
 398 }
 399
 400 ssize_t btrfs_getxattr(struct dentry *dentry, const char *name,
 401                        void *buffer, size_t size)
 402 {
 403         int ret;
 404
 405         /*
 406          * If this is a request for a synthetic attribute in the system.*
 407          * namespace use the generic infrastructure to resolve a handler
 408          * for it via sb->s_xattr.
 409          */
 410         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
 411                 return generic_getxattr(dentry, name, buffer, size);
 412
 413         ret = btrfs_is_valid_xattr(name);
 414         if (ret)
 415                 return ret;
 416         return __btrfs_getxattr(d_inode(dentry), name, buffer, size);
 417 }
 418
 419 int btrfs_setxattr(struct dentry *dentry, const char *name, const void *value,
 420                    size_t size, int flags)
 421 {
 422         struct btrfs_root *root = BTRFS_I(d_inode(dentry))->root;
 423         int ret;
 424
 425         /*
 426          * The permission on security.* and system.* is not checked
 427          * in permission().
 428          */
 429         if (btrfs_root_readonly(root))
 430                 return -EROFS;
 431
 432         /*
 433          * If this is a request for a synthetic attribute in the system.*
 434          * namespace use the generic infrastructure to resolve a handler
 435          * for it via sb->s_xattr.
 436          */
 437         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
 438                 return generic_setxattr(dentry, name, value, size, flags);
 439
 440         ret = btrfs_is_valid_xattr(name);
 441         if (ret)
 442                 return ret;
 443
 444         if (!strncmp(name, XATTR_BTRFS_PREFIX, XATTR_BTRFS_PREFIX_LEN))
 445                 return btrfs_set_prop(d_inode(dentry), name,
 446                                       value, size, flags);
 447
 448         if (size == 0)
 449                 value = "";  /* empty EA, do not remove */
 450
 451         return __btrfs_setxattr(NULL, d_inode(dentry), name, value, size,
 452                                 flags);
 453 }
 454
 455 int btrfs_removexattr(struct dentry *dentry, const char *name)
 456 {
 457         struct btrfs_root *root = BTRFS_I(d_inode(dentry))->root;
 458         int ret;
 459
 460         /*
 461          * The permission on security.* and system.* is not checked
 462          * in permission().
 463          */
 464         if (btrfs_root_readonly(root))
 465                 return -EROFS;
 466
 467         /*
 468          * If this is a request for a synthetic attribute in the system.*
 469          * namespace use the generic infrastructure to resolve a handler
 470          * for it via sb->s_xattr.
 471          */
 472         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
 473                 return generic_removexattr(dentry, name);
 474
 475         ret = btrfs_is_valid_xattr(name);
 476         if (ret)
 477                 return ret;
 478
 479         if (!strncmp(name, XATTR_BTRFS_PREFIX, XATTR_BTRFS_PREFIX_LEN))
 480                 return btrfs_set_prop(d_inode(dentry), name,
 481                                       NULL, 0, XATTR_REPLACE);
 482
 483         return __btrfs_setxattr(NULL, d_inode(dentry), name, NULL, 0,
 484                                 XATTR_REPLACE);
 485 }
 486
 487 static int btrfs_initxattrs(struct inode *inode,
 488                             const struct xattr *xattr_array, void *fs_info)
 489 {
 490         const struct xattr *xattr;
 491         struct btrfs_trans_handle *trans = fs_info;
 492         char *name;
 493         int err = 0;
 494
 495         for (xattr = xattr_array; xattr->name != NULL; xattr++) {
 496                 name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
 497                                strlen(xattr->name) + 1, GFP_NOFS);
 498                 if (!name) {
 499                         err = -ENOMEM;
 500                         break;
 501                 }
 502                 strcpy(name, XATTR_SECURITY_PREFIX);
 503                 strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
 504                 err = __btrfs_setxattr(trans, inode, name,
 505                                        xattr->value, xattr->value_len, 0);
 506                 kfree(name);
 507                 if (err < 0)
 508                         break;
 509         }
 510         return err;
 511 }
 512
 513 int btrfs_xattr_security_init(struct btrfs_trans_handle *trans,
 514                               struct inode *inode, struct inode *dir,
 515                               const struct qstr *qstr)
 516 {
 517         return security_inode_init_security(inode, dir, qstr,
 518                                             &btrfs_initxattrs, trans);
 519 }