3.16.83-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Johannes Thumshirn <jthumshirn@xxxxxxx>
commit 349ae63f40638a28c6fce52e8447c2d14b84cc0c upstream.
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.
Code inspection showed a RAID1 block group has the same issues.
Fixes: e06cd3dd7cea ("Btrfs: add validadtion checks for chunk loading")
Reviewed-by: Qu Wenruo <wqu@xxxxxxxx>
Reviewed-by: Nikolay Borisov <nborisov@xxxxxxxx>
Signed-off-by: Johannes Thumshirn <jthumshirn@xxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
fs/btrfs/volumes.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -5884,10 +5884,10 @@ static int btrfs_check_chunk_valid(struc
}
if ((type & BTRFS_BLOCK_GROUP_RAID10 && sub_stripes != 2) ||
- (type & BTRFS_BLOCK_GROUP_RAID1 && num_stripes < 1) ||
+ (type & BTRFS_BLOCK_GROUP_RAID1 && num_stripes != 2) ||
(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(root->fs_info,
