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>

drivers/s390/net/qeth_core_main.c

@@ -572,6 +572,10 @@ static void qeth_send_control_data_cb(struct qeth_channel *channel,
 	card = CARD_FROM_CDEV(channel->ccwdev);
 	if (qeth_check_idx_response(iob->data)) {
 		qeth_clear_ipacmd_list(card);
+		if (((iob->data[2] & 0xc0) == 0xc0) && iob->data[4] == 0xf6)
+			dev_err(&card->gdev->dev,
+				"The qeth device is not configured "
+				"for the OSI layer required by z/VM\n");
 		qeth_schedule_recovery(card);
 		goto out;
 	}

drivers/s390/net/qeth_l2_main.c

@@ -1126,9 +1126,11 @@ static int qeth_l2_recover(void *ptr)
 		dev_info(&card->gdev->dev,
 			"Device successfully recovered!\n");
 	else {
-		rtnl_lock();
-		dev_close(card->dev);
-		rtnl_unlock();
+		if (card->dev) {
+			rtnl_lock();
+			dev_close(card->dev);
+			rtnl_unlock();
+		}
 		dev_warn(&card->gdev->dev, "The qeth device driver "
 			"failed to recover an error on the device\n");
 	}

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);