net: remove ifalias on empty given alias

This patch removes the potentially allocated ifalias when the (new) given alias is empty.

E.g. when setting

echo "" > /sys/class/net/eth0/ifalias
Signed-off-by: NOliver Hartkopp <oliver@hartkopp.net>
Acked-by: NStephen Hemminger <shemminger@vyatta.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -967,6 +967,14 @@ int dev_set_alias(struct net_device *dev, const char *alias, size_t len)
 	if (len >= IFALIASZ)
 		return -EINVAL;
 
+	if (!len) {
+		if (dev->ifalias) {
+			kfree(dev->ifalias);
+			dev->ifalias = NULL;
+		}
+		return 0;
+	}
+
 	dev->ifalias = krealloc(dev->ifalias, len+1, GFP_KERNEL);
 	if (!dev->ifalias)
 		return -ENOMEM;