[4.2.y-ckt stable] Patch "dm: fix rq_end_stats() NULL pointer in dm_requeue_original_request()" has been added to the 4.2.y-ckt tree

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    dm: fix rq_end_stats() NULL pointer in dm_requeue_original_request()

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt7.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

>From 701aaef57ad56c558f609b619f44b2ba75e8730a Mon Sep 17 00:00:00 2001
From: "Bryn M. Reeves" <bmr at redhat.com>
Date: Mon, 14 Mar 2016 17:04:34 -0400
Subject: dm: fix rq_end_stats() NULL pointer in dm_requeue_original_request()

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 at redhat.com>
Signed-off-by: Mike Snitzer <snitzer at redhat.com>
Fixes: e262f34741 ("dm stats: add support for request-based DM devices")
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 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);
 	dm_unprep_request(rq);

-	rq_end_stats(md, rq);
 	if (!rq->q->mq_ops)
 		old_requeue_request(rq);
 	else {
--
2.7.4