diff options
author | NeilBrown <neilb@suse.com> | 2018-02-15 10:00:15 +0100 |
---|---|---|
committer | Mike Snitzer <snitzer@redhat.com> | 2018-02-16 16:46:35 +0100 |
commit | 8dd601fa8317243be887458c49f6c29c2f3d719f (patch) | |
tree | 0a354a696fd0f12ef5a405fe130a3349abd88217 /drivers/md | |
parent | Linux 4.16-rc1 (diff) | |
download | linux-8dd601fa8317243be887458c49f6c29c2f3d719f.tar.xz linux-8dd601fa8317243be887458c49f6c29c2f3d719f.zip |
dm: correctly handle chained bios in dec_pending()
dec_pending() is given an error status (possibly 0) to be recorded
against a bio. It can be called several times on the one 'struct
dm_io', and it is careful to only assign a non-zero error to
io->status. However when it then assigned io->status to bio->bi_status,
it is not careful and could overwrite a genuine error status with 0.
This can happen when chained bios are in use. If a bio is chained
beneath the bio that this dm_io is handling, the child bio might
complete and set bio->bi_status before the dm_io completes.
This has been possible since chained bios were introduced in 3.14, and
has become a lot easier to trigger with commit 18a25da84354 ("dm: ensure
bio submission follows a depth-first tree walk") as that commit caused
dm to start using chained bios itself.
A particular failure mode is that if a bio spans an 'error' target and a
working target, the 'error' fragment will complete instantly and set the
->bi_status, and the other fragment will normally complete a little
later, and will clear ->bi_status.
The fix is simply to only assign io_error to bio->bi_status when
io_error is not zero.
Reported-and-tested-by: Milan Broz <gmazyland@gmail.com>
Cc: stable@vger.kernel.org (v3.14+)
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'drivers/md')
-rw-r--r-- | drivers/md/dm.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/drivers/md/dm.c b/drivers/md/dm.c index d6de00f367ef..68136806d365 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -903,7 +903,8 @@ static void dec_pending(struct dm_io *io, blk_status_t error) queue_io(md, bio); } else { /* done with normal IO or empty flush */ - bio->bi_status = io_error; + if (io_error) + bio->bi_status = io_error; bio_endio(bio); } } |