[SRU][I][J][PATCH 1/1] s390/cio: verify the driver availability for path_event call

[Krzysztof Kozlowski]

From: Vineeth Vijayan <vneethv at linux.ibm.com>

BugLink: https://bugs.launchpad.net/bugs/1960875

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 at vger.kernel.org
Signed-off-by: Vineeth Vijayan <vneethv at linux.ibm.com>
Suggested-by: Peter Oberparleiter <oberpar at linux.ibm.com>
Reviewed-by: Jan Hoeppner <hoeppner at linux.ibm.com>
Reviewed-by: Peter Oberparleiter <oberpar at linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor at linux.ibm.com>
(cherry picked from commit dd9cb842fa9d90653a9b48aba52f89c069f3bc50)
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski at canonical.com>
---
 drivers/s390/cio/device.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/s390/cio/device.c b/drivers/s390/cio/device.c
index 84f659cafe76..ab734b66d008 100644
--- a/drivers/s390/cio/device.c
+++ b/drivers/s390/cio/device.c
@@ -1208,7 +1208,7 @@ static int io_subchannel_chp_event(struct subchannel *sch,
 			else
 				path_event[chpid] = PE_NONE;
 		}
-		if (cdev)
+		if (cdev && cdev->drv && cdev->drv->path_event)
 			cdev->drv->path_event(cdev, path_event);
 		break;
 	}
-- 
2.32.0