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         }
 126
 127 again:
 128         ret = btrfs_insert_xattr_item(trans, root, path, btrfs_ino(inode),
 129                                       name, name_len, value, size);
 130         if (ret == -EEXIST) {
 131                 if (flags & XATTR_CREATE)
 132                         goto out;
 133                 /*
 134                  * We can't use the path we already have since we won't have the
 135                  * proper locking for a delete, so release the path and
 136                  * re-lookup to delete the thing.
 137                  */
 138                 btrfs_release_path(path);
 139                 di = btrfs_lookup_xattr(trans, root, path, btrfs_ino(inode),
 140                                         name, name_len, -1);
 141                 if (IS_ERR(di)) {
 142                         ret = PTR_ERR(di);
 143                         goto out;
 144                 } else if (!di) {
 145                         /* Shouldn't happen but just in case... */
 146                         btrfs_release_path(path);
 147                         goto again;
 148                 }
 149
 150                 ret = btrfs_delete_one_dir_name(trans, root, path, di);
 151                 if (ret)
 152                         goto out;
 153
 154                 /*
 155                  * We have a value to set, so go back and try to insert it now.
 156                  */
 157                 if (value) {
 158                         btrfs_release_path(path);
 159                         goto again;
 160                 }
 161         }
 162 out:
 163         btrfs_free_path(path);
 164         return ret;
 165 }
 166
 167 /*
 168  * @value: "" makes the attribute to empty, NULL removes it
 169  */
 170 int __btrfs_setxattr(struct btrfs_trans_handle *trans,
 171                      struct inode *inode, const char *name,
 172                      const void *value, size_t size, int flags)
 173 {
 174         struct btrfs_root *root = BTRFS_I(inode)->root;
 175         int ret;
 176
 177         if (trans)
 178                 return do_setxattr(trans, inode, name, value, size, flags);
 179
 180         trans = btrfs_start_transaction(root, 2);
 181         if (IS_ERR(trans))
 182                 return PTR_ERR(trans);
 183
 184         ret = do_setxattr(trans, inode, name, value, size, flags);
 185         if (ret)
 186                 goto out;
 187
 188         inode->i_ctime = CURRENT_TIME;
 189         ret = btrfs_update_inode(trans, root, inode);
 190         BUG_ON(ret);
 191 out:
 192         btrfs_end_transaction_throttle(trans, root);
 193         return ret;
 194 }
 195
 196 ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
 197 {
 198         struct btrfs_key key, found_key;
 199         struct inode *inode = dentry->d_inode;
 200         struct btrfs_root *root = BTRFS_I(inode)->root;
 201         struct btrfs_path *path;
 202         struct extent_buffer *leaf;
 203         struct btrfs_dir_item *di;
 204         int ret = 0, slot;
 205         size_t total_size = 0, size_left = size;
 206         unsigned long name_ptr;
 207         size_t name_len;
 208
 209         /*
 210          * ok we want all objects associated with this id.
 211          * NOTE: we set key.offset = 0; because we want to start with the
 212          * first xattr that we find and walk forward
 213          */
 214         key.objectid = btrfs_ino(inode);
 215         btrfs_set_key_type(&key, BTRFS_XATTR_ITEM_KEY);
 216         key.offset = 0;
 217
 218         path = btrfs_alloc_path();
 219         if (!path)
 220                 return -ENOMEM;
 221         path->reada = 2;
 222
 223         /* search for our xattrs */
 224         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 225         if (ret < 0)
 226                 goto err;
 227
 228         while (1) {
 229                 leaf = path->nodes[0];
 230                 slot = path->slots[0];
 231
 232                 /* this is where we start walking through the path */
 233                 if (slot >= btrfs_header_nritems(leaf)) {
 234                         /*
 235                          * if we've reached the last slot in this leaf we need
 236                          * to go to the next leaf and reset everything
 237                          */
 238                         ret = btrfs_next_leaf(root, path);
 239                         if (ret < 0)
 240                                 goto err;
 241                         else if (ret > 0)
 242                                 break;
 243                         continue;
 244                 }
 245
 246                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
 247
 248                 /* check to make sure this item is what we want */
 249                 if (found_key.objectid != key.objectid)
 250                         break;
 251                 if (btrfs_key_type(&found_key) != BTRFS_XATTR_ITEM_KEY)
 252                         break;
 253
 254                 di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
 255                 if (verify_dir_item(root, leaf, di))
 256                         continue;
 257
 258                 name_len = btrfs_dir_name_len(leaf, di);
 259                 total_size += name_len + 1;
 260
 261                 /* we are just looking for how big our buffer needs to be */
 262                 if (!size)
 263                         goto next;
 264
 265                 if (!buffer || (name_len + 1) > size_left) {
 266                         ret = -ERANGE;
 267                         goto err;
 268                 }
 269
 270                 name_ptr = (unsigned long)(di + 1);
 271                 read_extent_buffer(leaf, buffer, name_ptr, name_len);
 272                 buffer[name_len] = '\0';
 273
 274                 size_left -= name_len + 1;
 275                 buffer += name_len + 1;
 276 next:
 277                 path->slots[0]++;
 278         }
 279         ret = total_size;
 280
 281 err:
 282         btrfs_free_path(path);
 283
 284         return ret;
 285 }
 286
 287 /*
 288  * List of handlers for synthetic system.* attributes.  All real ondisk
 289  * attributes are handled directly.
 290  */
 291 const struct xattr_handler *btrfs_xattr_handlers[] = {
 292 #ifdef CONFIG_BTRFS_FS_POSIX_ACL
 293         &btrfs_xattr_acl_access_handler,
 294         &btrfs_xattr_acl_default_handler,
 295 #endif
 296         NULL,
 297 };
 298
 299 /*
 300  * Check if the attribute is in a supported namespace.
 301  *
 302  * This applied after the check for the synthetic attributes in the system
 303  * namespace.
 304  */
 305 static bool btrfs_is_valid_xattr(const char *name)
 306 {
 307         return !strncmp(name, XATTR_SECURITY_PREFIX,
 308                         XATTR_SECURITY_PREFIX_LEN) ||
 309                !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN) ||
 310                !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) ||
 311                !strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN);
 312 }
 313
 314 ssize_t btrfs_getxattr(struct dentry *dentry, const char *name,
 315                        void *buffer, size_t size)
 316 {
 317         /*
 318          * If this is a request for a synthetic attribute in the system.*
 319          * namespace use the generic infrastructure to resolve a handler
 320          * for it via sb->s_xattr.
 321          */
 322         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
 323                 return generic_getxattr(dentry, name, buffer, size);
 324
 325         if (!btrfs_is_valid_xattr(name))
 326                 return -EOPNOTSUPP;
 327         return __btrfs_getxattr(dentry->d_inode, name, buffer, size);
 328 }
 329
 330 int btrfs_setxattr(struct dentry *dentry, const char *name, const void *value,
 331                    size_t size, int flags)
 332 {
 333         struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
 334
 335         /*
 336          * The permission on security.* and system.* is not checked
 337          * in permission().
 338          */
 339         if (btrfs_root_readonly(root))
 340                 return -EROFS;
 341
 342         /*
 343          * If this is a request for a synthetic attribute in the system.*
 344          * namespace use the generic infrastructure to resolve a handler
 345          * for it via sb->s_xattr.
 346          */
 347         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
 348                 return generic_setxattr(dentry, name, value, size, flags);
 349
 350         if (!btrfs_is_valid_xattr(name))
 351                 return -EOPNOTSUPP;
 352
 353         if (size == 0)
 354                 value = "";  /* empty EA, do not remove */
 355
 356         return __btrfs_setxattr(NULL, dentry->d_inode, name, value, size,
 357                                 flags);
 358 }
 359
 360 int btrfs_removexattr(struct dentry *dentry, const char *name)
 361 {
 362         struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
 363
 364         /*
 365          * The permission on security.* and system.* is not checked
 366          * in permission().
 367          */
 368         if (btrfs_root_readonly(root))
 369                 return -EROFS;
 370
 371         /*
 372          * If this is a request for a synthetic attribute in the system.*
 373          * namespace use the generic infrastructure to resolve a handler
 374          * for it via sb->s_xattr.
 375          */
 376         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
 377                 return generic_removexattr(dentry, name);
 378
 379         if (!btrfs_is_valid_xattr(name))
 380                 return -EOPNOTSUPP;
 381
 382         return __btrfs_setxattr(NULL, dentry->d_inode, name, NULL, 0,
 383                                 XATTR_REPLACE);
 384 }
 385
 386 int btrfs_xattr_security_init(struct btrfs_trans_handle *trans,
 387                               struct inode *inode, struct inode *dir,
 388                               const struct qstr *qstr)
 389 {
 390         int err;
 391         size_t len;
 392         void *value;
 393         char *suffix;
 394         char *name;
 395
 396         err = security_inode_init_security(inode, dir, qstr, &suffix, &value,
 397                                            &len);
 398         if (err) {
 399                 if (err == -EOPNOTSUPP)
 400                         return 0;
 401                 return err;
 402         }
 403
 404         name = kmalloc(XATTR_SECURITY_PREFIX_LEN + strlen(suffix) + 1,
 405                        GFP_NOFS);
 406         if (!name) {
 407                 err = -ENOMEM;
 408         } else {
 409                 strcpy(name, XATTR_SECURITY_PREFIX);
 410                 strcpy(name + XATTR_SECURITY_PREFIX_LEN, suffix);
 411                 err = __btrfs_setxattr(trans, inode, name, value, len, 0);
 412                 kfree(name);
 413         }
 414
 415         kfree(suffix);
 416         kfree(value);
 417         return err;
 418 }