[PATCH 4.19 079/114] dm delay: fix a crash when invalid device is specified

[Greg Kroah-Hartman]

From: Mikulas Patocka <mpato...@redhat.com>

commit 81bc6d150ace6250503b825d9d0c10f7bbd24095 upstream.

When the target line contains an invalid device, delay_ctr() will call
delay_dtr() with NULL workqueue.  Attempting to destroy the NULL
workqueue causes a crash.

Signed-off-by: Mikulas Patocka <mpato...@redhat.com>
Cc: sta...@vger.kernel.org
Signed-off-by: Mike Snitzer <snit...@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 drivers/md/dm-delay.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/md/dm-delay.c
+++ b/drivers/md/dm-delay.c
@@ -121,7 +121,8 @@ static void delay_dtr(struct dm_target *
 {
        struct delay_c *dc = ti->private;
 
-       destroy_workqueue(dc->kdelayd_wq);
+       if (dc->kdelayd_wq)
+               destroy_workqueue(dc->kdelayd_wq);
 
        if (dc->read.dev)
                dm_put_device(ti, dc->read.dev);