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 block group -> chunk mapping check, to ensure we have a completely matching (start, len, flags) chunk for each block group at mount time. Here we reuse the original find_first_block_group(), which is already doing basic bg -> chunk check, adding more check on start/len and type flags. Link: https://bugzilla.kernel.org/show_bug.cgi?id=199837 Reported-by: Xu Wen <wen.xu@xxxxxxxxxx> Signed-off-by: Qu Wenruo <wqu@xxxxxxxx> --- changelog: v2: Reuse existing find_first_block_group() to do the verification, pointed out by Gu. --- fs/btrfs/extent-tree.c | 29 ++++++++++++++++++++++++++++- 1 file changed, 28 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 3d9fe58c0080..63a6b5d36ac1 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -9717,6 +9717,8 @@ static int find_first_block_group(struct btrfs_fs_info *fs_info, int ret = 0; struct btrfs_key found_key; struct extent_buffer *leaf; + struct btrfs_block_group_item bg; + u64 flags; int slot; ret = btrfs_search_slot(NULL, root, key, path, 0, 0); @@ -9751,8 +9753,33 @@ static int find_first_block_group(struct btrfs_fs_info *fs_info, "logical %llu len %llu found bg but no related chunk", found_key.objectid, found_key.offset); ret = -ENOENT; + } else if (em->start != found_key.objectid || + em->len != found_key.offset) { + btrfs_err(fs_info, + "block group %llu len %llu mismatch with chunk %llu len %llu", + found_key.objectid, found_key.offset, + em->start, em->len); + ret = -EUCLEAN; } else { - ret = 0; + read_extent_buffer(leaf, &bg, + btrfs_item_ptr_offset(leaf, slot), + sizeof(bg)); + flags = btrfs_block_group_flags(&bg) & + BTRFS_BLOCK_GROUP_TYPE_MASK; + + if (flags != (em->map_lookup->type & + BTRFS_BLOCK_GROUP_TYPE_MASK)) { + btrfs_err(fs_info, +"block group %llu len %llu type flags 0x%llx mismatch with chunk type flags 0x%llx", + found_key.objectid, + found_key.offset, + flags, + (BTRFS_BLOCK_GROUP_TYPE_MASK & + em->map_lookup->type)); + ret = -EUCLEAN; + } else { + ret = 0; + } } free_extent_map(em); goto out; -- 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
