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* [PATCH] btrfs: ensure that a DUP block group has exactly two stripes
@ 2019-02-13 14:26 Johannes Thumshirn
  2019-02-13 14:27 ` Nikolay Borisov
                   ` (2 more replies)
  0 siblings, 3 replies; 9+ messages in thread
From: Johannes Thumshirn @ 2019-02-13 14:26 UTC (permalink / raw)
  To: David Sterba; +Cc: Linux BTRFS Mailinglist, Johannes Thumshirn, Liu Bo

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@gmail.com>
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
---
 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


^ permalink raw reply related	[flat|nested] 9+ messages in thread

end of thread, other threads:[~2019-02-15 15:18 UTC | newest]

Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-02-13 14:26 [PATCH] btrfs: ensure that a DUP block group has exactly two stripes Johannes Thumshirn
2019-02-13 14:27 ` Nikolay Borisov
2019-02-13 14:32 ` Qu Wenruo
2019-02-13 14:32 ` Hans van Kranenburg
2019-02-13 14:37   ` Johannes Thumshirn
2019-02-13 15:02     ` Nikolay Borisov
2019-02-14 17:27     ` Hans van Kranenburg
2019-02-14 16:21   ` Johannes Thumshirn
2019-02-15 15:20     ` David Sterba

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