s390/cio: derive cdev information only for IO-subchannels

[ Upstream commit 0c3812c ]

cdev->online for the purge function must not be checked for the
non-IO subchannel type. Make sure that we are deriving the cdev only
from sch-type SUBCHANNEL_TYPE_IO.

Signed-off-by: Vineeth Vijayan <vneethv@linux.ibm.com>
Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Stable-dep-of: 1b60741 ("s390/cio: fix out-of-bounds access on cio_ignore free")
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/s390/cio/css.c

@@ -792,10 +792,13 @@ static int __unset_online(struct device *dev, void *data)
 {
 	struct idset *set = data;
 	struct subchannel *sch = to_subchannel(dev);
-	struct ccw_device *cdev = sch_get_cdev(sch);
+	struct ccw_device *cdev;
 
-	if (cdev && cdev->online)
-		idset_sch_del(set, sch->schid);
+	if (sch->st == SUBCHANNEL_TYPE_IO) {
+		cdev = sch_get_cdev(sch);
+		if (cdev && cdev->online)
+			idset_sch_del(set, sch->schid);
+	}
 
 	return 0;
 }