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 "ctree.h"
  26 #include "btrfs_inode.h"
  27 #include "transaction.h"
  28 #include "xattr.h"
  29 #include "disk-io.h"
  30
  31
  32 ssize_t __btrfs_getxattr(struct inode *inode, const char *name,
  33                                 void *buffer, size_t size)
  34 {
  35         struct btrfs_dir_item *di;
  36         struct btrfs_root *root = BTRFS_I(inode)->root;
  37         struct btrfs_path *path;
  38         struct extent_buffer *leaf;
  39         int ret = 0;
  40         unsigned long data_ptr;
  41
  42         path = btrfs_alloc_path();
  43         if (!path)
  44                 return -ENOMEM;
  45
  46         /* lookup the xattr by name */
  47         di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(inode), name,
  48                                 strlen(name), 0);
  49         if (!di) {
  50                 ret = -ENODATA;
  51                 goto out;
  52         } else if (IS_ERR(di)) {
  53                 ret = PTR_ERR(di);
  54                 goto out;
  55         }
  56
  57         leaf = path->nodes[0];
  58         /* if size is 0, that means we want the size of the attr */
  59         if (!size) {
  60                 ret = btrfs_dir_data_len(leaf, di);
  61                 goto out;
  62         }
  63
  64         /* now get the data out of our dir_item */
  65         if (btrfs_dir_data_len(leaf, di) > size) {
  66                 ret = -ERANGE;
  67                 goto out;
  68         }
  69
  70         /*
  71          * The way things are packed into the leaf is like this
  72          * |struct btrfs_dir_item|name|data|
  73          * where name is the xattr name, so security.foo, and data is the
  74          * content of the xattr.  data_ptr points to the location in memory
  75          * where the data starts in the in memory leaf
  76          */
  77         data_ptr = (unsigned long)((char *)(di + 1) +
  78                                    btrfs_dir_name_len(leaf, di));
  79         read_extent_buffer(leaf, buffer, data_ptr,
  80                            btrfs_dir_data_len(leaf, di));
  81         ret = btrfs_dir_data_len(leaf, di);
  82
  83 out:
  84         btrfs_free_path(path);
  85         return ret;
  86 }
  87
  88 static int do_setxattr(struct btrfs_trans_handle *trans,
  89                        struct inode *inode, const char *name,
  90                        const void *value, size_t size, int flags)
  91 {
  92         struct btrfs_dir_item *di;
  93         struct btrfs_root *root = BTRFS_I(inode)->root;
  94         struct btrfs_path *path;
  95         size_t name_len = strlen(name);
  96         int ret = 0;
  97
  98         if (name_len + size > BTRFS_MAX_XATTR_SIZE(root))
  99                 return -ENOSPC;
 100
 101         path = btrfs_alloc_path();
 102         if (!path)
 103                 return -ENOMEM;
 104
 105         if (flags & XATTR_REPLACE) {
 106                 di = btrfs_lookup_xattr(trans, root, path, btrfs_ino(inode), name,
 107                                         name_len, -1);
 108                 if (IS_ERR(di)) {
 109                         ret = PTR_ERR(di);
 110                         goto out;
 111                 } else if (!di) {
 112                         ret = -ENODATA;
 113                         goto out;
 114                 }
 115                 ret = btrfs_delete_one_dir_name(trans, root, path, di);
 116                 if (ret)
 117                         goto out;
 118                 btrfs_release_path(path);
 119
 120                 /*
 121                  * remove the attribute
 122                  */
 123                 if (!value)
 124                         goto out;
 125         } else {
 126                 di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(inode),
 127                                         name, name_len, 0);
 128                 if (IS_ERR(di)) {
 129                         ret = PTR_ERR(di);
 130                         goto out;
 131                 }
 132                 if (!di && !value)
 133                         goto out;
 134                 btrfs_release_path(path);
 135         }
 136
 137 again:
 138         ret = btrfs_insert_xattr_item(trans, root, path, btrfs_ino(inode),
 139                                       name, name_len, value, size);
 140         /*
 141          * If we're setting an xattr to a new value but the new value is say
 142          * exactly BTRFS_MAX_XATTR_SIZE, we could end up with EOVERFLOW getting
 143          * back from split_leaf.  This is because it thinks we'll be extending
 144          * the existing item size, but we're asking for enough space to add the
 145          * item itself.  So if we get EOVERFLOW just set ret to EEXIST and let
 146          * the rest of the function figure it out.
 147          */
 148         if (ret == -EOVERFLOW)
 149                 ret = -EEXIST;
 150
 151         if (ret == -EEXIST) {
 152                 if (flags & XATTR_CREATE)
 153                         goto out;
 154                 /*
 155                  * We can't use the path we already have since we won't have the
 156                  * proper locking for a delete, so release the path and
 157                  * re-lookup to delete the thing.
 158                  */
 159                 btrfs_release_path(path);
 160                 di = btrfs_lookup_xattr(trans, root, path, btrfs_ino(inode),
 161                                         name, name_len, -1);
 162                 if (IS_ERR(di)) {
 163                         ret = PTR_ERR(di);
 164                         goto out;
 165                 } else if (!di) {
 166                         /* Shouldn't happen but just in case... */
 167                         btrfs_release_path(path);
 168                         goto again;
 169                 }
 170
 171                 ret = btrfs_delete_one_dir_name(trans, root, path, di);
 172                 if (ret)
 173                         goto out;
 174
 175                 /*
 176                  * We have a value to set, so go back and try to insert it now.
 177                  */
 178                 if (value) {
 179                         btrfs_release_path(path);
 180                         goto again;
 181                 }
 182         }
 183 out:
 184         btrfs_free_path(path);
 185         return ret;
 186 }
 187
 188 /*
 189  * @value: "" makes the attribute to empty, NULL removes it
 190  */
 191 int __btrfs_setxattr(struct btrfs_trans_handle *trans,
 192                      struct inode *inode, const char *name,
 193                      const void *value, size_t size, int flags)
 194 {
 195         struct btrfs_root *root = BTRFS_I(inode)->root;
 196         int ret;
 197
 198         if (trans)
 199                 return do_setxattr(trans, inode, name, value, size, flags);
 200
 201         trans = btrfs_start_transaction(root, 2);
 202         if (IS_ERR(trans))
 203                 return PTR_ERR(trans);
 204
 205         ret = do_setxattr(trans, inode, name, value, size, flags);
 206         if (ret)
 207                 goto out;
 208
 209         inode_inc_iversion(inode);
 210         inode->i_ctime = CURRENT_TIME;
 211         set_bit(BTRFS_INODE_COPY_EVERYTHING, &BTRFS_I(inode)->runtime_flags);
 212         ret = btrfs_update_inode(trans, root, inode);
 213         BUG_ON(ret);
 214 out:
 215         btrfs_end_transaction(trans, root);
 216         return ret;
 217 }
 218
 219 ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
 220 {
 221         struct btrfs_key key, found_key;
 222         struct inode *inode = dentry->d_inode;
 223         struct btrfs_root *root = BTRFS_I(inode)->root;
 224         struct btrfs_path *path;
 225         struct extent_buffer *leaf;
 226         struct btrfs_dir_item *di;
 227         int ret = 0, slot;
 228         size_t total_size = 0, size_left = size;
 229         unsigned long name_ptr;
 230         size_t name_len;
 231
 232         /*
 233          * ok we want all objects associated with this id.
 234          * NOTE: we set key.offset = 0; because we want to start with the
 235          * first xattr that we find and walk forward
 236          */
 237         key.objectid = btrfs_ino(inode);
 238         btrfs_set_key_type(&key, BTRFS_XATTR_ITEM_KEY);
 239         key.offset = 0;
 240
 241         path = btrfs_alloc_path();
 242         if (!path)
 243                 return -ENOMEM;
 244         path->reada = 2;
 245
 246         /* search for our xattrs */
 247         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 248         if (ret < 0)
 249                 goto err;
 250
 251         while (1) {
 252                 leaf = path->nodes[0];
 253                 slot = path->slots[0];
 254
 255                 /* this is where we start walking through the path */
 256                 if (slot >= btrfs_header_nritems(leaf)) {
 257                         /*
 258                          * if we've reached the last slot in this leaf we need
 259                          * to go to the next leaf and reset everything
 260                          */
 261                         ret = btrfs_next_leaf(root, path);
 262                         if (ret < 0)
 263                                 goto err;
 264                         else if (ret > 0)
 265                                 break;
 266                         continue;
 267                 }
 268
 269                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
 270
 271                 /* check to make sure this item is what we want */
 272                 if (found_key.objectid != key.objectid)
 273                         break;
 274                 if (btrfs_key_type(&found_key) != BTRFS_XATTR_ITEM_KEY)
 275                         break;
 276
 277                 di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
 278                 if (verify_dir_item(root, leaf, di))
 279                         goto next;
 280
 281                 name_len = btrfs_dir_name_len(leaf, di);
 282                 total_size += name_len + 1;
 283
 284                 /* we are just looking for how big our buffer needs to be */
 285                 if (!size)
 286                         goto next;
 287
 288                 if (!buffer || (name_len + 1) > size_left) {
 289                         ret = -ERANGE;
 290                         goto err;
 291                 }
 292
 293                 name_ptr = (unsigned long)(di + 1);
 294                 read_extent_buffer(leaf, buffer, name_ptr, name_len);
 295                 buffer[name_len] = '\0';
 296
 297                 size_left -= name_len + 1;
 298                 buffer += name_len + 1;
 299 next:
 300                 path->slots[0]++;
 301         }
 302         ret = total_size;
 303
 304 err:
 305         btrfs_free_path(path);
 306
 307         return ret;
 308 }
 309
 310 /*
 311  * List of handlers for synthetic system.* attributes.  All real ondisk
 312  * attributes are handled directly.
 313  */
 314 const struct xattr_handler *btrfs_xattr_handlers[] = {
 315 #ifdef CONFIG_BTRFS_FS_POSIX_ACL
 316         &btrfs_xattr_acl_access_handler,
 317         &btrfs_xattr_acl_default_handler,
 318 #endif
 319         NULL,
 320 };
 321
 322 /*
 323  * Check if the attribute is in a supported namespace.
 324  *
 325  * This applied after the check for the synthetic attributes in the system
 326  * namespace.
 327  */
 328 static bool btrfs_is_valid_xattr(const char *name)
 329 {
 330         return !strncmp(name, XATTR_SECURITY_PREFIX,
 331                         XATTR_SECURITY_PREFIX_LEN) ||
 332                !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN) ||
 333                !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) ||
 334                !strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN);
 335 }
 336
 337 ssize_t btrfs_getxattr(struct dentry *dentry, const char *name,
 338                        void *buffer, size_t size)
 339 {
 340         /*
 341          * If this is a request for a synthetic attribute in the system.*
 342          * namespace use the generic infrastructure to resolve a handler
 343          * for it via sb->s_xattr.
 344          */
 345         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
 346                 return generic_getxattr(dentry, name, buffer, size);
 347
 348         if (!btrfs_is_valid_xattr(name))
 349                 return -EOPNOTSUPP;
 350         return __btrfs_getxattr(dentry->d_inode, name, buffer, size);
 351 }
 352
 353 int btrfs_setxattr(struct dentry *dentry, const char *name, const void *value,
 354                    size_t size, int flags)
 355 {
 356         struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
 357
 358         /*
 359          * The permission on security.* and system.* is not checked
 360          * in permission().
 361          */
 362         if (btrfs_root_readonly(root))
 363                 return -EROFS;
 364
 365         /*
 366          * If this is a request for a synthetic attribute in the system.*
 367          * namespace use the generic infrastructure to resolve a handler
 368          * for it via sb->s_xattr.
 369          */
 370         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
 371                 return generic_setxattr(dentry, name, value, size, flags);
 372
 373         if (!btrfs_is_valid_xattr(name))
 374                 return -EOPNOTSUPP;
 375
 376         if (size == 0)
 377                 value = "";  /* empty EA, do not remove */
 378
 379         return __btrfs_setxattr(NULL, dentry->d_inode, name, value, size,
 380                                 flags);
 381 }
 382
 383 int btrfs_removexattr(struct dentry *dentry, const char *name)
 384 {
 385         struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
 386
 387         /*
 388          * The permission on security.* and system.* is not checked
 389          * in permission().
 390          */
 391         if (btrfs_root_readonly(root))
 392                 return -EROFS;
 393
 394         /*
 395          * If this is a request for a synthetic attribute in the system.*
 396          * namespace use the generic infrastructure to resolve a handler
 397          * for it via sb->s_xattr.
 398          */
 399         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
 400                 return generic_removexattr(dentry, name);
 401
 402         if (!btrfs_is_valid_xattr(name))
 403                 return -EOPNOTSUPP;
 404
 405         return __btrfs_setxattr(NULL, dentry->d_inode, name, NULL, 0,
 406                                 XATTR_REPLACE);
 407 }
 408
 409 static int btrfs_initxattrs(struct inode *inode,
 410                             const struct xattr *xattr_array, void *fs_info)
 411 {
 412         const struct xattr *xattr;
 413         struct btrfs_trans_handle *trans = fs_info;
 414         char *name;
 415         int err = 0;
 416
 417         for (xattr = xattr_array; xattr->name != NULL; xattr++) {
 418                 name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
 419                                strlen(xattr->name) + 1, GFP_NOFS);
 420                 if (!name) {
 421                         err = -ENOMEM;
 422                         break;
 423                 }
 424                 strcpy(name, XATTR_SECURITY_PREFIX);
 425                 strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
 426                 err = __btrfs_setxattr(trans, inode, name,
 427                                        xattr->value, xattr->value_len, 0);
 428                 kfree(name);
 429                 if (err < 0)
 430                         break;
 431         }
 432         return err;
 433 }
 434
 435 int btrfs_xattr_security_init(struct btrfs_trans_handle *trans,
 436                               struct inode *inode, struct inode *dir,
 437                               const struct qstr *qstr)
 438 {
 439         return security_inode_init_security(inode, dir, qstr,
 440                                             &btrfs_initxattrs, trans);
 441 }