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, inode->i_ino, 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         /* first lets see if we already have this xattr */
 106         di = btrfs_lookup_xattr(trans, root, path, inode->i_ino, name,
 107                                 strlen(name), -1);
 108         if (IS_ERR(di)) {
 109                 ret = PTR_ERR(di);
 110                 goto out;
 111         }
 112
 113         /* ok we already have this xattr, lets remove it */
 114         if (di) {
 115                 /* if we want create only exit */
 116                 if (flags & XATTR_CREATE) {
 117                         ret = -EEXIST;
 118                         goto out;
 119                 }
 120
 121                 ret = btrfs_delete_one_dir_name(trans, root, path, di);
 122                 BUG_ON(ret);
 123                 btrfs_release_path(root, path);
 124
 125                 /* if we don't have a value then we are removing the xattr */
 126                 if (!value)
 127                         goto out;
 128         } else {
 129                 btrfs_release_path(root, path);
 130
 131                 if (flags & XATTR_REPLACE) {
 132                         /* we couldn't find the attr to replace */
 133                         ret = -ENODATA;
 134                         goto out;
 135                 }
 136         }
 137
 138         /* ok we have to create a completely new xattr */
 139         ret = btrfs_insert_xattr_item(trans, root, path, inode->i_ino,
 140                                       name, name_len, value, size);
 141         BUG_ON(ret);
 142 out:
 143         btrfs_free_path(path);
 144         return ret;
 145 }
 146
 147 int __btrfs_setxattr(struct btrfs_trans_handle *trans,
 148                      struct inode *inode, const char *name,
 149                      const void *value, size_t size, int flags)
 150 {
 151         struct btrfs_root *root = BTRFS_I(inode)->root;
 152         int ret;
 153
 154         if (trans)
 155                 return do_setxattr(trans, inode, name, value, size, flags);
 156
 157         trans = btrfs_start_transaction(root, 2);
 158         if (IS_ERR(trans))
 159                 return PTR_ERR(trans);
 160
 161         btrfs_set_trans_block_group(trans, inode);
 162
 163         ret = do_setxattr(trans, inode, name, value, size, flags);
 164         if (ret)
 165                 goto out;
 166
 167         inode->i_ctime = CURRENT_TIME;
 168         ret = btrfs_update_inode(trans, root, inode);
 169         BUG_ON(ret);
 170 out:
 171         btrfs_end_transaction_throttle(trans, root);
 172         return ret;
 173 }
 174
 175 ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
 176 {
 177         struct btrfs_key key, found_key;
 178         struct inode *inode = dentry->d_inode;
 179         struct btrfs_root *root = BTRFS_I(inode)->root;
 180         struct btrfs_path *path;
 181         struct extent_buffer *leaf;
 182         struct btrfs_dir_item *di;
 183         int ret = 0, slot, advance;
 184         size_t total_size = 0, size_left = size;
 185         unsigned long name_ptr;
 186         size_t name_len;
 187         u32 nritems;
 188
 189         /*
 190          * ok we want all objects associated with this id.
 191          * NOTE: we set key.offset = 0; because we want to start with the
 192          * first xattr that we find and walk forward
 193          */
 194         key.objectid = inode->i_ino;
 195         btrfs_set_key_type(&key, BTRFS_XATTR_ITEM_KEY);
 196         key.offset = 0;
 197
 198         path = btrfs_alloc_path();
 199         if (!path)
 200                 return -ENOMEM;
 201         path->reada = 2;
 202
 203         /* search for our xattrs */
 204         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 205         if (ret < 0)
 206                 goto err;
 207         advance = 0;
 208         while (1) {
 209                 leaf = path->nodes[0];
 210                 nritems = btrfs_header_nritems(leaf);
 211                 slot = path->slots[0];
 212
 213                 /* this is where we start walking through the path */
 214                 if (advance || slot >= nritems) {
 215                         /*
 216                          * if we've reached the last slot in this leaf we need
 217                          * to go to the next leaf and reset everything
 218                          */
 219                         if (slot >= nritems-1) {
 220                                 ret = btrfs_next_leaf(root, path);
 221                                 if (ret)
 222                                         break;
 223                                 leaf = path->nodes[0];
 224                                 nritems = btrfs_header_nritems(leaf);
 225                                 slot = path->slots[0];
 226                         } else {
 227                                 /*
 228                                  * just walking through the slots on this leaf
 229                                  */
 230                                 slot++;
 231                                 path->slots[0]++;
 232                         }
 233                 }
 234                 advance = 1;
 235
 236                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
 237
 238                 /* check to make sure this item is what we want */
 239                 if (found_key.objectid != key.objectid)
 240                         break;
 241                 if (btrfs_key_type(&found_key) != BTRFS_XATTR_ITEM_KEY)
 242                         break;
 243
 244                 di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
 245
 246                 name_len = btrfs_dir_name_len(leaf, di);
 247                 total_size += name_len + 1;
 248
 249                 /* we are just looking for how big our buffer needs to be */
 250                 if (!size)
 251                         continue;
 252
 253                 if (!buffer || (name_len + 1) > size_left) {
 254                         ret = -ERANGE;
 255                         goto err;
 256                 }
 257
 258                 name_ptr = (unsigned long)(di + 1);
 259                 read_extent_buffer(leaf, buffer, name_ptr, name_len);
 260                 buffer[name_len] = '\0';
 261
 262                 size_left -= name_len + 1;
 263                 buffer += name_len + 1;
 264         }
 265         ret = total_size;
 266
 267 err:
 268         btrfs_free_path(path);
 269
 270         return ret;
 271 }
 272
 273 /*
 274  * List of handlers for synthetic system.* attributes.  All real ondisk
 275  * attributes are handled directly.
 276  */
 277 const struct xattr_handler *btrfs_xattr_handlers[] = {
 278 #ifdef CONFIG_BTRFS_FS_POSIX_ACL
 279         &btrfs_xattr_acl_access_handler,
 280         &btrfs_xattr_acl_default_handler,
 281 #endif
 282         NULL,
 283 };
 284
 285 /*
 286  * Check if the attribute is in a supported namespace.
 287  *
 288  * This applied after the check for the synthetic attributes in the system
 289  * namespace.
 290  */
 291 static bool btrfs_is_valid_xattr(const char *name)
 292 {
 293         return !strncmp(name, XATTR_SECURITY_PREFIX,
 294                         XATTR_SECURITY_PREFIX_LEN) ||
 295                !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN) ||
 296                !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) ||
 297                !strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN);
 298 }
 299
 300 ssize_t btrfs_getxattr(struct dentry *dentry, const char *name,
 301                        void *buffer, size_t size)
 302 {
 303         /*
 304          * If this is a request for a synthetic attribute in the system.*
 305          * namespace use the generic infrastructure to resolve a handler
 306          * for it via sb->s_xattr.
 307          */
 308         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
 309                 return generic_getxattr(dentry, name, buffer, size);
 310
 311         if (!btrfs_is_valid_xattr(name))
 312                 return -EOPNOTSUPP;
 313         return __btrfs_getxattr(dentry->d_inode, name, buffer, size);
 314 }
 315
 316 int btrfs_setxattr(struct dentry *dentry, const char *name, const void *value,
 317                    size_t size, int flags)
 318 {
 319         struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
 320
 321         /*
 322          * The permission on security.* and system.* is not checked
 323          * in permission().
 324          */
 325         if (btrfs_root_readonly(root))
 326                 return -EROFS;
 327
 328         /*
 329          * If this is a request for a synthetic attribute in the system.*
 330          * namespace use the generic infrastructure to resolve a handler
 331          * for it via sb->s_xattr.
 332          */
 333         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
 334                 return generic_setxattr(dentry, name, value, size, flags);
 335
 336         if (!btrfs_is_valid_xattr(name))
 337                 return -EOPNOTSUPP;
 338
 339         if (size == 0)
 340                 value = "";  /* empty EA, do not remove */
 341
 342         return __btrfs_setxattr(NULL, dentry->d_inode, name, value, size,
 343                                 flags);
 344 }
 345
 346 int btrfs_removexattr(struct dentry *dentry, const char *name)
 347 {
 348         struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
 349
 350         /*
 351          * The permission on security.* and system.* is not checked
 352          * in permission().
 353          */
 354         if (btrfs_root_readonly(root))
 355                 return -EROFS;
 356
 357         /*
 358          * If this is a request for a synthetic attribute in the system.*
 359          * namespace use the generic infrastructure to resolve a handler
 360          * for it via sb->s_xattr.
 361          */
 362         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
 363                 return generic_removexattr(dentry, name);
 364
 365         if (!btrfs_is_valid_xattr(name))
 366                 return -EOPNOTSUPP;
 367
 368         return __btrfs_setxattr(NULL, dentry->d_inode, name, NULL, 0,
 369                                 XATTR_REPLACE);
 370 }
 371
 372 int btrfs_xattr_security_init(struct btrfs_trans_handle *trans,
 373                               struct inode *inode, struct inode *dir)
 374 {
 375         int err;
 376         size_t len;
 377         void *value;
 378         char *suffix;
 379         char *name;
 380
 381         err = security_inode_init_security(inode, dir, &suffix, &value, &len);
 382         if (err) {
 383                 if (err == -EOPNOTSUPP)
 384                         return 0;
 385                 return err;
 386         }
 387
 388         name = kmalloc(XATTR_SECURITY_PREFIX_LEN + strlen(suffix) + 1,
 389                        GFP_NOFS);
 390         if (!name) {
 391                 err = -ENOMEM;
 392         } else {
 393                 strcpy(name, XATTR_SECURITY_PREFIX);
 394                 strcpy(name + XATTR_SECURITY_PREFIX_LEN, suffix);
 395                 err = __btrfs_setxattr(trans, inode, name, value, len, 0);
 396                 kfree(name);
 397         }
 398
 399         kfree(suffix);
 400         kfree(value);
 401         return err;
 402 }