Reported in https://bugzilla.kernel.org/show_bug.cgi?id=199837, if a crafted btrfs with incorrect chunk<->block group mapping, it could leads to a lot of unexpected behavior. Although the crafted image can be catched by block group item checker added in "[PATCH] btrfs: tree-checker: Verify block_group_item", if one crafted a valid enough block group item which can pass above check but still mismatch with existing chunk, it could cause a lot of undefined behavior. This patch will add extra chunk<->block group mapping check at mount time, so such problem can be detected early and cause no harm. Reported-by: Xu Wen <wen.xu@xxxxxxxxxx> Signed-off-by: Qu Wenruo <wqu@xxxxxxxx> --- fs/btrfs/extent-tree.c | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 3d9fe58c0080..7a11dc76cd6d 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -10003,6 +10003,31 @@ btrfs_create_block_group_cache(struct btrfs_fs_info *fs_info, return cache; } +static int verify_chunk_block_group_mapping(struct btrfs_fs_info *fs_info, + u64 start, u64 len) +{ + struct btrfs_mapping_tree *map_tree = &fs_info->mapping_tree; + struct extent_map *em; + int ret; + + read_lock(&map_tree->map_tree.lock); + em = lookup_extent_mapping(&map_tree->map_tree, start, len); + read_unlock(&map_tree->map_tree.lock); + + if (!em) { + ret = -ENOENT; + goto out; + } + if (em->start != start || em->len != len) { + ret = -ENOENT; + goto out; + } + ret = 0; +out: + free_extent_map(em); + return ret; +} + int btrfs_read_block_groups(struct btrfs_fs_info *info) { struct btrfs_path *path; @@ -10045,6 +10070,19 @@ int btrfs_read_block_groups(struct btrfs_fs_info *info) leaf = path->nodes[0]; btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]); + /* + * Since block group and chunks are 1:1 mapped and are core + * infrastructure of btrfs, we need to do extra verification. + */ + ret = verify_chunk_block_group_mapping(info, + found_key.objectid, found_key.offset); + if (ret < 0) { + btrfs_err_rl(info, + "block group start=%llu len=%llu doesn't have matched chunk", + found_key.objectid, found_key.offset); + goto error; + } + cache = btrfs_create_block_group_cache(info, found_key.objectid, found_key.offset); if (!cache) { -- 2.18.0 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
