[IPSEC]: Fix reversed ICMP6 policy check

The policy check I added for ICMP on IPv6 is reversed.  This
patch fixes that.

It also adds an skb->sp check so that unprotected packets that
fail the policy check do not crash the machine.
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/icmp.c

@@ -977,7 +977,7 @@ int icmp_rcv(struct sk_buff *skb)
 	struct icmphdr *icmph;
 	struct rtable *rt = (struct rtable *)skb->dst;
 
-	if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb) &&
+	if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb) && skb->sp &&
 	    skb->sp->xvec[skb->sp->len - 1]->props.flags & XFRM_STATE_ICMP) {
 		int nh;
 

net/ipv6/icmp.c

@@ -644,7 +644,7 @@ static int icmpv6_rcv(struct sk_buff *skb)
 	struct icmp6hdr *hdr;
 	int type;
 
-	if (xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb) &&
+	if (!xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb) && skb->sp &&
 	    skb->sp->xvec[skb->sp->len - 1]->props.flags & XFRM_STATE_ICMP) {
 		int nh;