4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Qu Wenruo <wqu@xxxxxxxx> commit ba480dd4db9f1798541eb2d1c423fc95feee8d36 upstream. A crafted image has empty root tree block, which will later cause 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 as it contains the mapping. 3) Fs tree At least inode item for top level inode (.). 4) Device tree Dev extents for chunks 5) Extent tree Must have corresponding extent for each chunk. If any of them 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.xu@xxxxxxxxxx> Signed-off-by: Qu Wenruo <wqu@xxxxxxxx> Tested-by: Gu Jinxiang <gujx@xxxxxxxxxxxxxx> Reviewed-by: David Sterba <dsterba@xxxxxxxx> Signed-off-by: David Sterba <dsterba@xxxxxxxx> [bwh: Backported to 4.4: Pass root instead of fs_info to generic_err()] Signed-off-by: Ben Hutchings <ben.hutchings@xxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/btrfs/tree-checker.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) --- a/fs/btrfs/tree-checker.c +++ b/fs/btrfs/tree-checker.c @@ -456,9 +456,22 @@ static int check_leaf(struct btrfs_root * skip this check for relocation trees. */ if (nritems == 0 && !btrfs_header_flag(leaf, BTRFS_HEADER_FLAG_RELOC)) { + u64 owner = btrfs_header_owner(leaf); struct btrfs_root *check_root; - key.objectid = btrfs_header_owner(leaf); + /* These trees must 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 || + owner == BTRFS_DATA_RELOC_TREE_OBJECTID) { + generic_err(root, leaf, 0, + "invalid root, root %llu must never be empty", + owner); + return -EUCLEAN; + } + key.objectid = owner; key.type = BTRFS_ROOT_ITEM_KEY; key.offset = (u64)-1;
