Although only RAID10 use sub_stripes, a hostile attack can modify chunk
tree and just add RAID10 bit to a single chunk.
Then btrfs_map_block will trigger a 0 division in kernel and destroy
everything.
Just add extra check when reading chunk from disk.
Reported-by: Lukas Lueg <lukas.l...@gmail.com>
Signed-off-by: Qu Wenruo <quwen...@cn.fujitsu.com>
---
v2:
Return -EIO, and add kernel message output.
---
fs/btrfs/volumes.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 8222f6f..fdcecf7 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -6061,6 +6061,17 @@ static int read_one_chunk(struct btrfs_root *root,
struct btrfs_key *key,
map->stripe_len = btrfs_chunk_stripe_len(leaf, chunk);
map->type = btrfs_chunk_type(leaf, chunk);
map->sub_stripes = btrfs_chunk_sub_stripes(leaf, chunk);
+
+ /* Add extra check to avoid hostile 0 division attack */
+ if (map->type & BTRFS_BLOCK_GROUP_RAID10 &&
+ map->sub_stripes == 0) {
+ btrfs_warn(root->fs_info,
+ "RAID10 chunk found but with no sub stripe for
bytenr: %llu\n",
+ logical);
+ free_extent_map(em);
+ return -EIO;
+ }
+
for (i = 0; i < num_stripes; i++) {
map->stripes[i].physical =
btrfs_stripe_offset_nr(leaf, chunk, i);
--
2.3.5
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