netfilter: ctnetlink: fix possible refcount leak in ctnetlink_create_conntrack()

nf_ct_put() needs to be called to put the refcount got by
nf_conntrack_find_get() to avoid refcount leak when
nf_conntrack_hash_check_insert() fails.

Fixes: 7d367e06688d ("netfilter: ctnetlink: fix soft lockup when netlink adds new entries (v2)")
Signed-off-by: Hangyu Hua <[e-mail]>
Acked-by: Florian Westphal <[e-mail]>
Signed-off-by: Pablo Neira Ayuso <[e-mail]>

net/netfilter/nf_conntrack_netlink.c

···
 
 	err = nf_conntrack_hash_check_insert(ct);
 	if (err < 0)
-		goto err2;
+		goto err3;
 
 	rcu_read_unlock();
 
 	return ct;
 
+err3:
+	if (ct->master)
+		nf_ct_put(ct->master);
 err2:
 	rcu_read_unlock();
 err1: