From: Vineeth Vijayan <vneethv@linux.ibm.com>
Date: Wed, 2 Feb 2022 21:45:56 +0100
Subject: s390/cio: verify the driver availability for path_event call
Git-commit: dd9cb842fa9d90653a9b48aba52f89c069f3bc50
Patch-mainline: v5.17-rc4
References: bsc#1195927 LTC#196420

If no driver is attached to a device or the driver does not provide the
path_event function, an FCES path-event on this device could end up in a
kernel-panic. Verify the driver availability before the path_event
function call.

Fixes: 32ef938815c1 ("s390/cio: Add support for FCES status notification")
Cc: stable@vger.kernel.org
Signed-off-by: Vineeth Vijayan <vneethv@linux.ibm.com>
Suggested-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Reviewed-by: Jan Hoeppner <hoeppner@linux.ibm.com>
Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/s390/cio/device.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/s390/cio/device.c
+++ b/drivers/s390/cio/device.c
@@ -1207,7 +1207,7 @@ static int io_subchannel_chp_event(struc
 			else
 				path_event[chpid] = PE_NONE;
 		}
-		if (cdev)
+		if (cdev && cdev->drv && cdev->drv->path_event)
 			cdev->drv->path_event(cdev, path_event);
 		break;
 	}