[PATCH 4.2.y-ckt 115/218] dm: fix rq_end_stats() NULL pointer in dm_requeue_original_request()

From: Kamal Mostafa
Date: Thu Mar 31 2016 - 16:52:43 EST

4.2.8-ckt7 -stable review patch. If anyone has any objections, please let me know.


From: "Bryn M. Reeves" <bmr@xxxxxxxxxx>

commit 98dbc9c6c61698792e3a66f32f3bf066201d42d7 upstream.

An "old" (.request_fn) DM 'struct request' stores a pointer to the
associated 'struct dm_rq_target_io' in rq->special.

dm_requeue_original_request(), previously named
dm_requeue_unmapped_original_request(), called dm_unprep_request() to
reset rq->special to NULL. But rq_end_stats() would go on to hit a NULL
pointer deference because its call to tio_from_request() returned NULL.

Fix this by calling rq_end_stats() _before_ dm_unprep_request()

Signed-off-by: Bryn M. Reeves <bmr@xxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Fixes: e262f34741 ("dm stats: add support for request-based DM devices")
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
drivers/md/dm.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 3f82998..e066983 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1184,9 +1184,9 @@ static void dm_requeue_original_request(struct mapped_device *md,
int rw = rq_data_dir(rq);

+ rq_end_stats(md, rq);

- rq_end_stats(md, rq);
if (!rq->q->mq_ops)
else {