From: Mikulas Patocka <mpatocka@xxxxxxxxxx> 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 <mpatocka@xxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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);