ipx: header length validation needed

This patch will linearize and check there is enough data.
It handles the pprop case as well as avoiding a whole audit of
the routing code.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>

net/ipx/af_ipx.c

@@ -1647,7 +1647,8 @@ static int ipx_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_ty
 	ipx_pktsize	= ntohs(ipx->ipx_pktsize);
 	
 	/* Too small or invalid header? */
-	if (ipx_pktsize < sizeof(struct ipxhdr) || ipx_pktsize > skb->len)
+	if (ipx_pktsize < sizeof(struct ipxhdr)
+	   || !pskb_may_pull(skb, ipx_pktsize))
 		goto drop;
                         
 	if (ipx->ipx_checksum != IPX_NO_CHECKSUM &&