[IPV4]: Fix inet6_dev reference leak in ndisc_dst_alloc error path.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/route.c

@@ -647,8 +647,10 @@ struct dst_entry *ndisc_dst_alloc(struct net_device *dev,
 		return NULL;
 
 	rt = ip6_dst_alloc();
-	if (unlikely(rt == NULL))
+	if (unlikely(rt == NULL)) {
+		in6_dev_put(idev);
 		goto out;
+	}
 
 	dev_hold(dev);
 	if (neigh)