vlan/macvlan: fix NULL pointer dereferences in ethtool handlers

Check whether the underlying device provides a set of ethtool ops before
checking for individual handlers to avoid NULL pointer dereferences.

Reported-by: Art van Breemen <ard@telegraafnet.nl>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c
index 1b34135..6b09213 100644
--- a/net/8021q/vlan_dev.c
+++ b/net/8021q/vlan_dev.c
@@ -668,7 +668,8 @@
 	const struct vlan_dev_info *vlan = vlan_dev_info(dev);
 	struct net_device *real_dev = vlan->real_dev;
 
-	if (!real_dev->ethtool_ops->get_settings)
+	if (!real_dev->ethtool_ops ||
+	    !real_dev->ethtool_ops->get_settings)
 		return -EOPNOTSUPP;
 
 	return real_dev->ethtool_ops->get_settings(real_dev, cmd);