qeth: avoid crash in case of layer mismatch for VSWITCH

For z/VM GuestLAN or VSWITCH devices the transport layer is
configured in z/VM. The layer2 attribute of a participating Linux
device has to match the z/VM definition. In case of a mismatch
Linux currently crashes in qeth recovery due to a reference to the
not yet existing net_device.
Solution: add a check for existence of net_device and add a message
pointing to the mismatch of layer definitions in Linux and z/VM.

Signed-off-by: Ursula Braun <ursula.braun@de.ibm.com>
Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 3 deletions

diff --git a/drivers/s390/net/qeth_l3_main.c b/drivers/s390/net/qeth_l3_main.c
index cdd6ab9c894d..8f30085ef5b4 100644
--- a/drivers/s390/net/qeth_l3_main.c
+++ b/drivers/s390/net/qeth_l3_main.c
@@ -2082,9 +2082,11 @@ static int qeth_l3_stop_card(struct qeth_card *card, int recovery_mode)
                 if (recovery_mode)
                         qeth_l3_stop(card->dev);
                 else {
-                        rtnl_lock();
-                        dev_close(card->dev);
-                        rtnl_unlock();
+                        if (card->dev) {
+                                rtnl_lock();
+                                dev_close(card->dev);
+                                rtnl_unlock();
+                        }
                 }
                 if (!card->use_hard_stop) {
                         rc = qeth_send_stoplan(card);