[PATCH] Fix for NAT core on nonlinear skbs

The nat core calls skb_ip_make_writable() with a length too short.
Found by nfsim.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

net/ipv4/netfilter/ip_nat_core.c

@@ -466,7 +466,7 @@ manip_pkt(u_int16_t proto,
 	struct iphdr *iph;
 
 	(*pskb)->nfcache |= NFC_ALTERED;
-	if (!skb_ip_make_writable(pskb, iphdroff+sizeof(iph)))
+	if (!skb_ip_make_writable(pskb, iphdroff+sizeof(*iph)))
 		return 0;
 
 	iph = (void *)(*pskb)->data + iphdroff;