netfilter: nf_queue: relax NFQA_CT attribute check

Allow modifying attributes of the conntrack associated with a packet
without first requesting ct data via CFG_F_CONNTRACK or extra
nfnetlink_conntrack socket.

Also remove unneded rcu_read_lock; the entire function is already
protected by rcu.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nfnetlink_queue_core.c

@@ -987,8 +987,7 @@ nfqnl_recv_verdict(struct sock *ctnl, struct sk_buff *skb,
 	if (entry == NULL)
 		return -ENOENT;
 
-	rcu_read_lock();
-	if (nfqa[NFQA_CT] && (queue->flags & NFQA_CFG_F_CONNTRACK))
+	if (nfqa[NFQA_CT])
 		ct = nfqnl_ct_parse(entry->skb, nfqa[NFQA_CT], &ctinfo);
 
 	if (nfqa[NFQA_PAYLOAD]) {
@@ -1002,7 +1001,6 @@ nfqnl_recv_verdict(struct sock *ctnl, struct sk_buff *skb,
 		if (ct)
 			nfqnl_ct_seq_adjust(skb, ct, ctinfo, diff);
 	}
-	rcu_read_unlock();
 
 	if (nfqa[NFQA_MARK])
 		entry->skb->mark = ntohl(nla_get_be32(nfqa[NFQA_MARK]));