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         /*
 131          * If we're setting an xattr to a new value but the new value is say
 132          * exactly BTRFS_MAX_XATTR_SIZE, we could end up with EOVERFLOW getting
 133          * back from split_leaf.  This is because it thinks we'll be extending
 134          * the existing item size, but we're asking for enough space to add the
 135          * item itself.  So if we get EOVERFLOW just set ret to EEXIST and let
 136          * the rest of the function figure it out.
 137          */
 138         if (ret == -EOVERFLOW)
 139                 ret = -EEXIST;
 140
 141         if (ret == -EEXIST) {
 142                 if (flags & XATTR_CREATE)
 143                         goto out;
 144                 /*
 145                  * We can't use the path we already have since we won't have the
 146                  * proper locking for a delete, so release the path and
 147                  * re-lookup to delete the thing.
 148                  */
 149                 btrfs_release_path(path);
 150                 di = btrfs_lookup_xattr(trans, root, path, btrfs_ino(inode),
 151                                         name, name_len, -1);
 152                 if (IS_ERR(di)) {
 153                         ret = PTR_ERR(di);
 154                         goto out;
 155                 } else if (!di) {
 156                         /* Shouldn't happen but just in case... */
 157                         btrfs_release_path(path);
 158                         goto again;
 159                 }
 160
 161                 ret = btrfs_delete_one_dir_name(trans, root, path, di);
 162                 if (ret)
 163                         goto out;
 164
 165                 /*
 166                  * We have a value to set, so go back and try to insert it now.
 167                  */
 168                 if (value) {
 169                         btrfs_release_path(path);
 170                         goto again;
 171                 }
 172         }
 173 out:
 174         btrfs_free_path(path);
 175         return ret;
 176 }
 177
 178 /*
 179  * @value: "" makes the attribute to empty, NULL removes it
 180  */
 181 int __btrfs_setxattr(struct btrfs_trans_handle *trans,
 182                      struct inode *inode, const char *name,
 183                      const void *value, size_t size, int flags)
 184 {
 185         struct btrfs_root *root = BTRFS_I(inode)->root;
 186         int ret;
 187
 188         if (trans)
 189                 return do_setxattr(trans, inode, name, value, size, flags);
 190
 191         trans = btrfs_start_transaction(root, 2);
 192         if (IS_ERR(trans))
 193                 return PTR_ERR(trans);
 194
 195         ret = do_setxattr(trans, inode, name, value, size, flags);
 196         if (ret)
 197                 goto out;
 198
 199         inode->i_ctime = CURRENT_TIME;
 200         ret = btrfs_update_inode(trans, root, inode);
 201         BUG_ON(ret);
 202 out:
 203         btrfs_end_transaction_throttle(trans, root);
 204         return ret;
 205 }
 206
 207 ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
 208 {
 209         struct btrfs_key key, found_key;
 210         struct inode *inode = dentry->d_inode;
 211         struct btrfs_root *root = BTRFS_I(inode)->root;
 212         struct btrfs_path *path;
 213         struct extent_buffer *leaf;
 214         struct btrfs_dir_item *di;
 215         int ret = 0, slot;
 216         size_t total_size = 0, size_left = size;
 217         unsigned long name_ptr;
 218         size_t name_len;
 219
 220         /*
 221          * ok we want all objects associated with this id.
 222          * NOTE: we set key.offset = 0; because we want to start with the
 223          * first xattr that we find and walk forward
 224          */
 225         key.objectid = btrfs_ino(inode);
 226         btrfs_set_key_type(&key, BTRFS_XATTR_ITEM_KEY);
 227         key.offset = 0;
 228
 229         path = btrfs_alloc_path();
 230         if (!path)
 231                 return -ENOMEM;
 232         path->reada = 2;
 233
 234         /* search for our xattrs */
 235         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 236         if (ret < 0)
 237                 goto err;
 238
 239         while (1) {
 240                 leaf = path->nodes[0];
 241                 slot = path->slots[0];
 242
 243                 /* this is where we start walking through the path */
 244                 if (slot >= btrfs_header_nritems(leaf)) {
 245                         /*
 246                          * if we've reached the last slot in this leaf we need
 247                          * to go to the next leaf and reset everything
 248                          */
 249                         ret = btrfs_next_leaf(root, path);
 250                         if (ret < 0)
 251                                 goto err;
 252                         else if (ret > 0)
 253                                 break;
 254                         continue;
 255                 }
 256
 257                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
 258
 259                 /* check to make sure this item is what we want */
 260                 if (found_key.objectid != key.objectid)
 261                         break;
 262                 if (btrfs_key_type(&found_key) != BTRFS_XATTR_ITEM_KEY)
 263                         break;
 264
 265                 di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
 266                 if (verify_dir_item(root, leaf, di))
 267                         continue;
 268
 269                 name_len = btrfs_dir_name_len(leaf, di);
 270                 total_size += name_len + 1;
 271
 272                 /* we are just looking for how big our buffer needs to be */
 273                 if (!size)
 274                         goto next;
 275
 276                 if (!buffer || (name_len + 1) > size_left) {
 277                         ret = -ERANGE;
 278                         goto err;
 279                 }
 280
 281                 name_ptr = (unsigned long)(di + 1);
 282                 read_extent_buffer(leaf, buffer, name_ptr, name_len);
 283                 buffer[name_len] = '\0';
 284
 285                 size_left -= name_len + 1;
 286                 buffer += name_len + 1;
 287 next:
 288                 path->slots[0]++;
 289         }
 290         ret = total_size;
 291
 292 err:
 293         btrfs_free_path(path);
 294
 295         return ret;
 296 }
 297
 298 /*
 299  * List of handlers for synthetic system.* attributes.  All real ondisk
 300  * attributes are handled directly.
 301  */
 302 const struct xattr_handler *btrfs_xattr_handlers[] = {
 303 #ifdef CONFIG_BTRFS_FS_POSIX_ACL
 304         &btrfs_xattr_acl_access_handler,
 305         &btrfs_xattr_acl_default_handler,
 306 #endif
 307         NULL,
 308 };
 309
 310 /*
 311  * Check if the attribute is in a supported namespace.
 312  *
 313  * This applied after the check for the synthetic attributes in the system
 314  * namespace.
 315  */
 316 static bool btrfs_is_valid_xattr(const char *name)
 317 {
 318         return !strncmp(name, XATTR_SECURITY_PREFIX,
 319                         XATTR_SECURITY_PREFIX_LEN) ||
 320                !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN) ||
 321                !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) ||
 322                !strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN);
 323 }
 324
 325 ssize_t btrfs_getxattr(struct dentry *dentry, const char *name,
 326                        void *buffer, size_t size)
 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_getxattr(dentry, name, buffer, size);
 335
 336         if (!btrfs_is_valid_xattr(name))
 337                 return -EOPNOTSUPP;
 338         return __btrfs_getxattr(dentry->d_inode, name, buffer, size);
 339 }
 340
 341 int btrfs_setxattr(struct dentry *dentry, const char *name, const void *value,
 342                    size_t size, int flags)
 343 {
 344         struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
 345
 346         /*
 347          * The permission on security.* and system.* is not checked
 348          * in permission().
 349          */
 350         if (btrfs_root_readonly(root))
 351                 return -EROFS;
 352
 353         /*
 354          * If this is a request for a synthetic attribute in the system.*
 355          * namespace use the generic infrastructure to resolve a handler
 356          * for it via sb->s_xattr.
 357          */
 358         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
 359                 return generic_setxattr(dentry, name, value, size, flags);
 360
 361         if (!btrfs_is_valid_xattr(name))
 362                 return -EOPNOTSUPP;
 363
 364         if (size == 0)
 365                 value = "";  /* empty EA, do not remove */
 366
 367         return __btrfs_setxattr(NULL, dentry->d_inode, name, value, size,
 368                                 flags);
 369 }
 370
 371 int btrfs_removexattr(struct dentry *dentry, const char *name)
 372 {
 373         struct btrfs_root *root = BTRFS_I(dentry->d_inode)->root;
 374
 375         /*
 376          * The permission on security.* and system.* is not checked
 377          * in permission().
 378          */
 379         if (btrfs_root_readonly(root))
 380                 return -EROFS;
 381
 382         /*
 383          * If this is a request for a synthetic attribute in the system.*
 384          * namespace use the generic infrastructure to resolve a handler
 385          * for it via sb->s_xattr.
 386          */
 387         if (!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
 388                 return generic_removexattr(dentry, name);
 389
 390         if (!btrfs_is_valid_xattr(name))
 391                 return -EOPNOTSUPP;
 392
 393         return __btrfs_setxattr(NULL, dentry->d_inode, name, NULL, 0,
 394                                 XATTR_REPLACE);
 395 }
 396
 397 int btrfs_initxattrs(struct inode *inode, const struct xattr *xattr_array,
 398                      void *fs_info)
 399 {
 400         const struct xattr *xattr;
 401         struct btrfs_trans_handle *trans = fs_info;
 402         char *name;
 403         int err = 0;
 404
 405         for (xattr = xattr_array; xattr->name != NULL; xattr++) {
 406                 name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
 407                                strlen(xattr->name) + 1, GFP_NOFS);
 408                 if (!name) {
 409                         err = -ENOMEM;
 410                         break;
 411                 }
 412                 strcpy(name, XATTR_SECURITY_PREFIX);
 413                 strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
 414                 err = __btrfs_setxattr(trans, inode, name,
 415                                        xattr->value, xattr->value_len, 0);
 416                 kfree(name);
 417                 if (err < 0)
 418                         break;
 419         }
 420         return err;
 421 }
 422
 423 int btrfs_xattr_security_init(struct btrfs_trans_handle *trans,
 424                               struct inode *inode, struct inode *dir,
 425                               const struct qstr *qstr)
 426 {
 427         return security_inode_init_security(inode, dir, qstr,
 428                                             &btrfs_initxattrs, trans);
 429 }