From: Mike Snitzer <snitzer@redhat.com>
Date: Wed, 25 Jan 2017 15:24:52 +0000 (+0100)
Subject: dm rq: cope with DM device destruction while in dm_old_request_fn()
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=4087a1fffe38106e10646606a27f10d40451862d;p=linux-beck.git

dm rq: cope with DM device destruction while in dm_old_request_fn()

Fixes a crash in dm_table_find_target() due to a NULL struct dm_table
being passed from dm_old_request_fn() that races with DM device
destruction.

Reported-by: artem@flashgrid.io
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
---

diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index 9d7275fb541a..6e702fc69a83 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -779,6 +779,10 @@ static void dm_old_request_fn(struct request_queue *q)
 		int srcu_idx;
 		struct dm_table *map = dm_get_live_table(md, &srcu_idx);
 
+		if (unlikely(!map)) {
+			dm_put_live_table(md, srcu_idx);
+			return;
+		}
 		ti = dm_table_find_target(map, pos);
 		dm_put_live_table(md, srcu_idx);
 	}