On 3.07.2018 12:10, Qu Wenruo wrote:
> A crafted image has empty root tree block, which will cause later NULL
> pointer dereference.
>
> The following trees should never be empty:
> 1) Tree root
> Must contain at least root items for extent tree, device tree and fs
> tree
>
> 2) Chunk tree
> Or we can't even bootstrap.
>
> 3) Fs tree
> At least inode item for top level inode (.).
>
> 4) Device tree
> Dev extents for chunks
>
> 5) Extent tree
> Must has corresponding extent for each chunk.
>
> If any is empty, we are sure the fs is corrupted and no need to mount
> it.
>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=199847
> Reported-by: Xu Wen <wen...@gatech.edu>
> Signed-off-by: Qu Wenruo <w...@suse.com>
> ---
> fs/btrfs/tree-checker.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c
> index 1cd735b099df..3a307efab46b 100644
> --- a/fs/btrfs/tree-checker.c
> +++ b/fs/btrfs/tree-checker.c
> @@ -497,8 +497,20 @@ static int check_leaf(struct btrfs_fs_info *fs_info,
> struct extent_buffer *leaf,
> * skip this check for relocation trees.
> */
> if (nritems == 0 && !btrfs_header_flag(leaf, BTRFS_HEADER_FLAG_RELOC)) {
> + u64 owner = btrfs_header_owner(leaf);
nit: Since you assign the owner of the leaf to a variable use this
variable when initialising key object below.
> struct btrfs_root *check_root;
>
> + /* These trees should never be empty */
> + if (owner == BTRFS_ROOT_TREE_OBJECTID ||
> + owner == BTRFS_CHUNK_TREE_OBJECTID ||
> + owner == BTRFS_EXTENT_TREE_OBJECTID ||
> + owner == BTRFS_DEV_TREE_OBJECTID ||
> + owner == BTRFS_FS_TREE_OBJECTID) {
> + generic_err(fs_info, leaf, 0,
> + "invalid root, root %llu should never be empty",
> + owner);
> + return -EUCLEAN;
> + }
> key.objectid = btrfs_header_owner(leaf);
> key.type = BTRFS_ROOT_ITEM_KEY;
> key.offset = (u64)-1;
>
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