--- udp.c.orig	2015-07-19 09:28:16.732477245 +0800
+++ udp.c	2015-07-19 09:29:46.952441957 +0800
@@ -894,7 +894,7 @@
 	struct sk_buff *skb;
 	struct ip_options_data opt_copy;
 
-	if (len > 0xFFFF)
+	if (len > (0xFFFF - sizeof(struct udphdr) - sizeof(struct iphdr)))
 		return -EMSGSIZE;
 
 	/*