[PATCH 4.4 37/40] s390/dasd: check for device error pointer within state change interrupts

[Greg Kroah-Hartman]

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

------------------

From: Stefan Haberland <sth@xxxxxxxxxxxxxxxxxx>


[ Upstream commit 2202134e48a3b50320aeb9e3dd1186833e9d7e66 ]

Check if the device pointer is valid. Just a sanity check since we already
are in the int handler of the device.

Signed-off-by: Stefan Haberland <sth@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/s390/block/dasd.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/drivers/s390/block/dasd.c
+++ b/drivers/s390/block/dasd.c
@@ -1635,8 +1635,11 @@ void dasd_int_handler(struct ccw_device
 	/* check for for attention message */
 	if (scsw_dstat(&irb->scsw) & DEV_STAT_ATTENTION) {
 		device = dasd_device_from_cdev_locked(cdev);
-		device->discipline->check_attention(device, irb->esw.esw1.lpum);
-		dasd_put_device(device);
+		if (!IS_ERR(device)) {
+			device->discipline->check_attention(device,
+							    irb->esw.esw1.lpum);
+			dasd_put_device(device);
+		}
 	}
 
 	if (!cqr)