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 <linux/posix_acl_xattr.h>
  26 #include "ctree.h"
  27 #include "btrfs_inode.h"
  28 #include "transaction.h"
  29 #include "xattr.h"
  30 #include "disk-io.h"
  31 #include "props.h"
  32 #include "locking.h"
  33
  34
  35 ssize_t __btrfs_getxattr(struct inode *inode, const char *name,
  36                                 void *buffer, size_t size)
  37 {
  38         struct btrfs_dir_item *di;
  39         struct btrfs_root *root = BTRFS_I(inode)->root;
  40         struct btrfs_path *path;
  41         struct extent_buffer *leaf;
  42         int ret = 0;
  43         unsigned long data_ptr;
  44
  45         path = btrfs_alloc_path();
  46         if (!path)
  47                 return -ENOMEM;
  48
  49         /* lookup the xattr by name */
  50         di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(BTRFS_I(inode)),
  51                         name, strlen(name), 0);
  52         if (!di) {
  53                 ret = -ENODATA;
  54                 goto out;
  55         } else if (IS_ERR(di)) {
  56                 ret = PTR_ERR(di);
  57                 goto out;
  58         }
  59
  60         leaf = path->nodes[0];
  61         /* if size is 0, that means we want the size of the attr */
  62         if (!size) {
  63                 ret = btrfs_dir_data_len(leaf, di);
  64                 goto out;
  65         }
  66
  67         /* now get the data out of our dir_item */
  68         if (btrfs_dir_data_len(leaf, di) > size) {
  69                 ret = -ERANGE;
  70                 goto out;
  71         }
  72
  73         /*
  74          * The way things are packed into the leaf is like this
  75          * |struct btrfs_dir_item|name|data|
  76          * where name is the xattr name, so security.foo, and data is the
  77          * content of the xattr.  data_ptr points to the location in memory
  78          * where the data starts in the in memory leaf
  79          */
  80         data_ptr = (unsigned long)((char *)(di + 1) +
  81                                    btrfs_dir_name_len(leaf, di));
  82         read_extent_buffer(leaf, buffer, data_ptr,
  83                            btrfs_dir_data_len(leaf, di));
  84         ret = btrfs_dir_data_len(leaf, di);
  85
  86 out:
  87         btrfs_free_path(path);
  88         return ret;
  89 }
  90
  91 static int do_setxattr(struct btrfs_trans_handle *trans,
  92                        struct inode *inode, const char *name,
  93                        const void *value, size_t size, int flags)
  94 {
  95         struct btrfs_dir_item *di = NULL;
  96         struct btrfs_root *root = BTRFS_I(inode)->root;
  97         struct btrfs_fs_info *fs_info = root->fs_info;
  98         struct btrfs_path *path;
  99         size_t name_len = strlen(name);
 100         int ret = 0;
 101
 102         if (name_len + size > BTRFS_MAX_XATTR_SIZE(root->fs_info))
 103                 return -ENOSPC;
 104
 105         path = btrfs_alloc_path();
 106         if (!path)
 107                 return -ENOMEM;
 108         path->skip_release_on_error = 1;
 109
 110         if (!value) {
 111                 di = btrfs_lookup_xattr(trans, root, path,
 112                                 btrfs_ino(BTRFS_I(inode)), name, name_len, -1);
 113                 if (!di && (flags & XATTR_REPLACE))
 114                         ret = -ENODATA;
 115                 else if (IS_ERR(di))
 116                         ret = PTR_ERR(di);
 117                 else if (di)
 118                         ret = btrfs_delete_one_dir_name(trans, root, path, di);
 119                 goto out;
 120         }
 121
 122         /*
 123          * For a replace we can't just do the insert blindly.
 124          * Do a lookup first (read-only btrfs_search_slot), and return if xattr
 125          * doesn't exist. If it exists, fall down below to the insert/replace
 126          * path - we can't race with a concurrent xattr delete, because the VFS
 127          * locks the inode's i_mutex before calling setxattr or removexattr.
 128          */
 129         if (flags & XATTR_REPLACE) {
 130                 ASSERT(inode_is_locked(inode));
 131                 di = btrfs_lookup_xattr(NULL, root, path,
 132                                 btrfs_ino(BTRFS_I(inode)), name, name_len, 0);
 133                 if (!di)
 134                         ret = -ENODATA;
 135                 else if (IS_ERR(di))
 136                         ret = PTR_ERR(di);
 137                 if (ret)
 138                         goto out;
 139                 btrfs_release_path(path);
 140                 di = NULL;
 141         }
 142
 143         ret = btrfs_insert_xattr_item(trans, root, path, btrfs_ino(BTRFS_I(inode)),
 144                                       name, name_len, value, size);
 145         if (ret == -EOVERFLOW) {
 146                 /*
 147                  * We have an existing item in a leaf, split_leaf couldn't
 148                  * expand it. That item might have or not a dir_item that
 149                  * matches our target xattr, so lets check.
 150                  */
 151                 ret = 0;
 152                 btrfs_assert_tree_locked(path->nodes[0]);
 153                 di = btrfs_match_dir_item_name(fs_info, path, name, name_len);
 154                 if (!di && !(flags & XATTR_REPLACE)) {
 155                         ret = -ENOSPC;
 156                         goto out;
 157                 }
 158         } else if (ret == -EEXIST) {
 159                 ret = 0;
 160                 di = btrfs_match_dir_item_name(fs_info, path, name, name_len);
 161                 ASSERT(di); /* logic error */
 162         } else if (ret) {
 163                 goto out;
 164         }
 165
 166         if (di && (flags & XATTR_CREATE)) {
 167                 ret = -EEXIST;
 168                 goto out;
 169         }
 170
 171         if (di) {
 172                 /*
 173                  * We're doing a replace, and it must be atomic, that is, at
 174                  * any point in time we have either the old or the new xattr
 175                  * value in the tree. We don't want readers (getxattr and
 176                  * listxattrs) to miss a value, this is specially important
 177                  * for ACLs.
 178                  */
 179                 const int slot = path->slots[0];
 180                 struct extent_buffer *leaf = path->nodes[0];
 181                 const u16 old_data_len = btrfs_dir_data_len(leaf, di);
 182                 const u32 item_size = btrfs_item_size_nr(leaf, slot);
 183                 const u32 data_size = sizeof(*di) + name_len + size;
 184                 struct btrfs_item *item;
 185                 unsigned long data_ptr;
 186                 char *ptr;
 187
 188                 if (size > old_data_len) {
 189                         if (btrfs_leaf_free_space(fs_info, leaf) <
 190                             (size - old_data_len)) {
 191                                 ret = -ENOSPC;
 192                                 goto out;
 193                         }
 194                 }
 195
 196                 if (old_data_len + name_len + sizeof(*di) == item_size) {
 197                         /* No other xattrs packed in the same leaf item. */
 198                         if (size > old_data_len)
 199                                 btrfs_extend_item(fs_info, path,
 200                                                   size - old_data_len);
 201                         else if (size < old_data_len)
 202                                 btrfs_truncate_item(fs_info, path,
 203                                                     data_size, 1);
 204                 } else {
 205                         /* There are other xattrs packed in the same item. */
 206                         ret = btrfs_delete_one_dir_name(trans, root, path, di);
 207                         if (ret)
 208                                 goto out;
 209                         btrfs_extend_item(fs_info, path, data_size);
 210                 }
 211
 212                 item = btrfs_item_nr(slot);
 213                 ptr = btrfs_item_ptr(leaf, slot, char);
 214                 ptr += btrfs_item_size(leaf, item) - data_size;
 215                 di = (struct btrfs_dir_item *)ptr;
 216                 btrfs_set_dir_data_len(leaf, di, size);
 217                 data_ptr = ((unsigned long)(di + 1)) + name_len;
 218                 write_extent_buffer(leaf, value, data_ptr, size);
 219                 btrfs_mark_buffer_dirty(leaf);
 220         } else {
 221                 /*
 222                  * Insert, and we had space for the xattr, so path->slots[0] is
 223                  * where our xattr dir_item is and btrfs_insert_xattr_item()
 224                  * filled it.
 225                  */
 226         }
 227 out:
 228         btrfs_free_path(path);
 229         return ret;
 230 }
 231
 232 /*
 233  * @value: "" makes the attribute to empty, NULL removes it
 234  */
 235 int __btrfs_setxattr(struct btrfs_trans_handle *trans,
 236                      struct inode *inode, const char *name,
 237                      const void *value, size_t size, int flags)
 238 {
 239         struct btrfs_root *root = BTRFS_I(inode)->root;
 240         int ret;
 241
 242         if (btrfs_root_readonly(root))
 243                 return -EROFS;
 244
 245         if (trans)
 246                 return do_setxattr(trans, inode, name, value, size, flags);
 247
 248         trans = btrfs_start_transaction(root, 2);
 249         if (IS_ERR(trans))
 250                 return PTR_ERR(trans);
 251
 252         ret = do_setxattr(trans, inode, name, value, size, flags);
 253         if (ret)
 254                 goto out;
 255
 256         inode_inc_iversion(inode);
 257         inode->i_ctime = current_time(inode);
 258         set_bit(BTRFS_INODE_COPY_EVERYTHING, &BTRFS_I(inode)->runtime_flags);
 259         ret = btrfs_update_inode(trans, root, inode);
 260         BUG_ON(ret);
 261 out:
 262         btrfs_end_transaction(trans);
 263         return ret;
 264 }
 265
 266 ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
 267 {
 268         struct btrfs_key key;
 269         struct inode *inode = d_inode(dentry);
 270         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 271         struct btrfs_root *root = BTRFS_I(inode)->root;
 272         struct btrfs_path *path;
 273         int ret = 0;
 274         size_t total_size = 0, size_left = size;
 275
 276         /*
 277          * ok we want all objects associated with this id.
 278          * NOTE: we set key.offset = 0; because we want to start with the
 279          * first xattr that we find and walk forward
 280          */
 281         key.objectid = btrfs_ino(BTRFS_I(inode));
 282         key.type = BTRFS_XATTR_ITEM_KEY;
 283         key.offset = 0;
 284
 285         path = btrfs_alloc_path();
 286         if (!path)
 287                 return -ENOMEM;
 288         path->reada = READA_FORWARD;
 289
 290         /* search for our xattrs */
 291         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 292         if (ret < 0)
 293                 goto err;
 294
 295         while (1) {
 296                 struct extent_buffer *leaf;
 297                 int slot;
 298                 struct btrfs_dir_item *di;
 299                 struct btrfs_key found_key;
 300                 u32 item_size;
 301                 u32 cur;
 302
 303                 leaf = path->nodes[0];
 304                 slot = path->slots[0];
 305
 306                 /* this is where we start walking through the path */
 307                 if (slot >= btrfs_header_nritems(leaf)) {
 308                         /*
 309                          * if we've reached the last slot in this leaf we need
 310                          * to go to the next leaf and reset everything
 311                          */
 312                         ret = btrfs_next_leaf(root, path);
 313                         if (ret < 0)
 314                                 goto err;
 315                         else if (ret > 0)
 316                                 break;
 317                         continue;
 318                 }
 319
 320                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
 321
 322                 /* check to make sure this item is what we want */
 323                 if (found_key.objectid != key.objectid)
 324                         break;
 325                 if (found_key.type > BTRFS_XATTR_ITEM_KEY)
 326                         break;
 327                 if (found_key.type < BTRFS_XATTR_ITEM_KEY)
 328                         goto next_item;
 329
 330                 di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
 331                 item_size = btrfs_item_size_nr(leaf, slot);
 332                 cur = 0;
 333                 while (cur < item_size) {
 334                         u16 name_len = btrfs_dir_name_len(leaf, di);
 335                         u16 data_len = btrfs_dir_data_len(leaf, di);
 336                         u32 this_len = sizeof(*di) + name_len + data_len;
 337                         unsigned long name_ptr = (unsigned long)(di + 1);
 338
 339                         if (verify_dir_item(fs_info, leaf, slot, di)) {
 340                                 ret = -EIO;
 341                                 goto err;
 342                         }
 343
 344                         total_size += name_len + 1;
 345                         /*
 346                          * We are just looking for how big our buffer needs to
 347                          * be.
 348                          */
 349                         if (!size)
 350                                 goto next;
 351
 352                         if (!buffer || (name_len + 1) > size_left) {
 353                                 ret = -ERANGE;
 354                                 goto err;
 355                         }
 356
 357                         read_extent_buffer(leaf, buffer, name_ptr, name_len);
 358                         buffer[name_len] = '\0';
 359
 360                         size_left -= name_len + 1;
 361                         buffer += name_len + 1;
 362 next:
 363                         cur += this_len;
 364                         di = (struct btrfs_dir_item *)((char *)di + this_len);
 365                 }
 366 next_item:
 367                 path->slots[0]++;
 368         }
 369         ret = total_size;
 370
 371 err:
 372         btrfs_free_path(path);
 373
 374         return ret;
 375 }
 376
 377 static int btrfs_xattr_handler_get(const struct xattr_handler *handler,
 378                                    struct dentry *unused, struct inode *inode,
 379                                    const char *name, void *buffer, size_t size)
 380 {
 381         name = xattr_full_name(handler, name);
 382         return __btrfs_getxattr(inode, name, buffer, size);
 383 }
 384
 385 static int btrfs_xattr_handler_set(const struct xattr_handler *handler,
 386                                    struct dentry *unused, struct inode *inode,
 387                                    const char *name, const void *buffer,
 388                                    size_t size, int flags)
 389 {
 390         name = xattr_full_name(handler, name);
 391         return __btrfs_setxattr(NULL, inode, name, buffer, size, flags);
 392 }
 393
 394 static int btrfs_xattr_handler_set_prop(const struct xattr_handler *handler,
 395                                         struct dentry *unused, struct inode *inode,
 396                                         const char *name, const void *value,
 397                                         size_t size, int flags)
 398 {
 399         name = xattr_full_name(handler, name);
 400         return btrfs_set_prop(inode, name, value, size, flags);
 401 }
 402
 403 static const struct xattr_handler btrfs_security_xattr_handler = {
 404         .prefix = XATTR_SECURITY_PREFIX,
 405         .get = btrfs_xattr_handler_get,
 406         .set = btrfs_xattr_handler_set,
 407 };
 408
 409 static const struct xattr_handler btrfs_trusted_xattr_handler = {
 410         .prefix = XATTR_TRUSTED_PREFIX,
 411         .get = btrfs_xattr_handler_get,
 412         .set = btrfs_xattr_handler_set,
 413 };
 414
 415 static const struct xattr_handler btrfs_user_xattr_handler = {
 416         .prefix = XATTR_USER_PREFIX,
 417         .get = btrfs_xattr_handler_get,
 418         .set = btrfs_xattr_handler_set,
 419 };
 420
 421 static const struct xattr_handler btrfs_btrfs_xattr_handler = {
 422         .prefix = XATTR_BTRFS_PREFIX,
 423         .get = btrfs_xattr_handler_get,
 424         .set = btrfs_xattr_handler_set_prop,
 425 };
 426
 427 const struct xattr_handler *btrfs_xattr_handlers[] = {
 428         &btrfs_security_xattr_handler,
 429 #ifdef CONFIG_BTRFS_FS_POSIX_ACL
 430         &posix_acl_access_xattr_handler,
 431         &posix_acl_default_xattr_handler,
 432 #endif
 433         &btrfs_trusted_xattr_handler,
 434         &btrfs_user_xattr_handler,
 435         &btrfs_btrfs_xattr_handler,
 436         NULL,
 437 };
 438
 439 static int btrfs_initxattrs(struct inode *inode,
 440                             const struct xattr *xattr_array, void *fs_info)
 441 {
 442         const struct xattr *xattr;
 443         struct btrfs_trans_handle *trans = fs_info;
 444         char *name;
 445         int err = 0;
 446
 447         for (xattr = xattr_array; xattr->name != NULL; xattr++) {
 448                 name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
 449                                strlen(xattr->name) + 1, GFP_KERNEL);
 450                 if (!name) {
 451                         err = -ENOMEM;
 452                         break;
 453                 }
 454                 strcpy(name, XATTR_SECURITY_PREFIX);
 455                 strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
 456                 err = __btrfs_setxattr(trans, inode, name,
 457                                        xattr->value, xattr->value_len, 0);
 458                 kfree(name);
 459                 if (err < 0)
 460                         break;
 461         }
 462         return err;
 463 }
 464
 465 int btrfs_xattr_security_init(struct btrfs_trans_handle *trans,
 466                               struct inode *inode, struct inode *dir,
 467                               const struct qstr *qstr)
 468 {
 469         return security_inode_init_security(inode, dir, qstr,
 470                                             &btrfs_initxattrs, trans);
 471 }