We recently had a customer issue with a corrupted filesystem. When trying
to mount this image btrfs panicked with a division by zero in
calc_stripe_length().
The corrupt chunk had a 'num_stripes' value of 1. calc_stripe_length()
takes this value and divides it by the number of copies the RAID profile is
expected to have to calculate the amount of data stripes. As a DUP profile
is expected to have 2 copies this division resulted in 1/2 = 0. Later then
the 'data_stripes' variable is used as a divisor in the stripe length
calculation which results in a division by 0 and thus a kernel panic.
When encountering a filesystem with a DUP block group and a 'num_stripes'
value unequal to 2, refuse mounting as the image is corrupted and will lead
to unexpected behaviour.
Fixes: e06cd3dd7cea ("Btrfs: add validadtion checks for chunk loading")
Cc: Liu Bo <obuil.liubo@xxxxxxxxx>
Signed-off-by: Johannes Thumshirn <jthumshirn@xxxxxxx>
---
fs/btrfs/volumes.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 03f223aa7194..b40cc7c830f4 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -6794,7 +6794,7 @@ static int btrfs_check_chunk_valid(struct btrfs_fs_info *fs_info,
(type & BTRFS_BLOCK_GROUP_RAID1 && num_stripes < 1) ||
(type & BTRFS_BLOCK_GROUP_RAID5 && num_stripes < 2) ||
(type & BTRFS_BLOCK_GROUP_RAID6 && num_stripes < 3) ||
- (type & BTRFS_BLOCK_GROUP_DUP && num_stripes > 2) ||
+ (type & BTRFS_BLOCK_GROUP_DUP && num_stripes != 2) ||
((type & BTRFS_BLOCK_GROUP_PROFILE_MASK) == 0 &&
num_stripes != 1)) {
btrfs_err(fs_info,
--
2.16.4
