ipv6: fix illegal mac_header comparison on 32bit

Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/skbuff.h

@@ -1741,6 +1741,11 @@ static inline void skb_set_mac_header(struct sk_buff *skb, const int offset)
 }
 #endif /* NET_SKBUFF_DATA_USES_OFFSET */
 
+static inline void skb_pop_mac_header(struct sk_buff *skb)
+{
+	skb->mac_header = skb->network_header;
+}
+
 static inline void skb_probe_transport_header(struct sk_buff *skb,
 					      const int offset_hint)
 {

net/ipv6/udp_offload.c

@@ -85,7 +85,7 @@ static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb,
 
 	/* Check if there is enough headroom to insert fragment header. */
 	tnl_hlen = skb_tnl_header_len(skb);
-	if (skb->mac_header < (tnl_hlen + frag_hdr_sz)) {
+	if (skb_mac_header(skb) < skb->head + tnl_hlen + frag_hdr_sz) {
 		if (gso_pskb_expand_head(skb, tnl_hlen + frag_hdr_sz))
 			goto out;
 	}