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