[NETFILTER] Fix ip_conntrack_proto_find_get badness

The function ip_conntrack_proto_find_get always returns a valid pointer. The 
generic protocol helper is returned when no specific protocol helper is found.
This patch fixes as well a missing putting at dump_protoinfo, when no to_attr
is found.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/ipv4/netfilter/ip_conntrack_netlink.c b/net/ipv4/netfilter/ip_conntrack_netlink.c
index f5e5e31..b797ef9 100644
--- a/net/ipv4/netfilter/ip_conntrack_netlink.c
+++ b/net/ipv4/netfilter/ip_conntrack_netlink.c
@@ -59,11 +59,13 @@ ctnetlink_dump_tuples_proto(struct sk_bu
 
 	NFA_PUT(skb, CTA_PROTO_NUM, sizeof(u_int8_t), &tuple->dst.protonum);
 
+	/* If no protocol helper is found, this function will return the
+	 * generic protocol helper, so proto won't *ever* be NULL */
 	proto = ip_conntrack_proto_find_get(tuple->dst.protonum);
-	if (likely(proto && proto->tuple_to_nfattr)) {
+	if (likely(proto->tuple_to_nfattr))
 		ret = proto->tuple_to_nfattr(skb, tuple);
-		ip_conntrack_proto_put(proto);
-	}
+
+	ip_conntrack_proto_put(proto);
 
 	return ret;
 
@@ -128,9 +130,11 @@ ctnetlink_dump_protoinfo(struct sk_buff 
 
 	struct nfattr *nest_proto;
 	int ret;
-	
-	if (!proto || !proto->to_nfattr)
+
+	if (!proto->to_nfattr) {
+		ip_conntrack_proto_put(proto);
 		return 0;
+	}
 	
 	nest_proto = NFA_NEST(skb, CTA_PROTOINFO);