vxlan: fix potential NULL dereference in arp_reduce()

This patch fixes a NULL pointer dereference in the event of an
skb allocation failure in arp_reduce().
Signed-Off-By: NDavid L Stevens <dlstevens@us.ibm.com>
Acked-by: NCong Wang <cwang@twopensource.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/vxlan.c

@@ -1318,6 +1318,9 @@ static int arp_reduce(struct net_device *dev, struct sk_buff *skb)
 
 		neigh_release(n);
 
+		if (reply == NULL)
+			goto out;
+
 		skb_reset_mac_header(reply);
 		__skb_pull(reply, skb_network_offset(reply));
 		reply->ip_summed = CHECKSUM_UNNECESSARY;