s390/qeth: cancel close_dev work before removing a card

A card's close_dev work is scheduled on a driver-wide workqueue. If the
card is removed and freed while the work is still active, this causes a
use-after-free.
So make sure that the work is completed before freeing the card.

Fixes: 0f54761d ("qeth: Support VEPA mode")
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/s390/net/qeth_core.h

@@ -22,6 +22,7 @@
 #include <linux/hashtable.h>
 #include <linux/ip.h>
 #include <linux/refcount.h>
+#include <linux/workqueue.h>
 
 #include <net/ipv6.h>
 #include <net/if_inet6.h>

drivers/s390/net/qeth_l2_main.c

@@ -801,6 +801,8 @@ static void qeth_l2_remove_device(struct ccwgroup_device *cgdev)
 
 	if (cgdev->state == CCWGROUP_ONLINE)
 		qeth_l2_set_offline(cgdev);
+
+	cancel_work_sync(&card->close_dev_work);
 	if (qeth_netdev_is_registered(card->dev))
 		unregister_netdev(card->dev);
 }

drivers/s390/net/qeth_l3_main.c

@@ -2338,6 +2338,7 @@ static void qeth_l3_remove_device(struct ccwgroup_device *cgdev)
 	if (cgdev->state == CCWGROUP_ONLINE)
 		qeth_l3_set_offline(cgdev);
 
+	cancel_work_sync(&card->close_dev_work);
 	if (qeth_netdev_is_registered(card->dev))
 		unregister_netdev(card->dev);
 	qeth_l3_clear_ip_htable(card, 0);