diff --git a/include/net/netfilter/nf_conntrack.h b/include/net/netfilter/nf_conntrack.h
index 8a2b0ae7dbd2..ab86036bbf0c 100644
--- a/include/net/netfilter/nf_conntrack.h
+++ b/include/net/netfilter/nf_conntrack.h
@@ -209,7 +209,7 @@ extern struct nf_conntrack_tuple_hash *
 __nf_conntrack_find(struct net *net, u16 zone,
 		    const struct nf_conntrack_tuple *tuple);
 
-extern void nf_conntrack_hash_insert(struct nf_conn *ct);
+extern int nf_conntrack_hash_check_insert(struct nf_conn *ct);
 extern void nf_ct_delete_from_lists(struct nf_conn *ct);
 extern void nf_ct_insert_dying_list(struct nf_conn *ct);
 
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 76613f5a55c0..ed86a3be678e 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -404,19 +404,49 @@ static void __nf_conntrack_hash_insert(struct nf_conn *ct,
 			   &net->ct.hash[repl_hash]);
 }
 
-void nf_conntrack_hash_insert(struct nf_conn *ct)
+int
+nf_conntrack_hash_check_insert(struct nf_conn *ct)
 {
 	struct net *net = nf_ct_net(ct);
 	unsigned int hash, repl_hash;
+	struct nf_conntrack_tuple_hash *h;
+	struct hlist_nulls_node *n;
 	u16 zone;
 
 	zone = nf_ct_zone(ct);
-	hash = hash_conntrack(net, zone, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
-	repl_hash = hash_conntrack(net, zone, &ct->tuplehash[IP_CT_DIR_REPLY].tuple);
+	hash = hash_conntrack(net, zone,
+			      &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
+	repl_hash = hash_conntrack(net, zone,
+				   &ct->tuplehash[IP_CT_DIR_REPLY].tuple);
 
+	spin_lock_bh(&nf_conntrack_lock);
+
+	/* See if there's one in the list already, including reverse */
+	hlist_nulls_for_each_entry(h, n, &net->ct.hash[hash], hnnode)
+		if (nf_ct_tuple_equal(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple,
+				      &h->tuple) &&
+		    zone == nf_ct_zone(nf_ct_tuplehash_to_ctrack(h)))
+			goto out;
+	hlist_nulls_for_each_entry(h, n, &net->ct.hash[repl_hash], hnnode)
+		if (nf_ct_tuple_equal(&ct->tuplehash[IP_CT_DIR_REPLY].tuple,
+				      &h->tuple) &&
+		    zone == nf_ct_zone(nf_ct_tuplehash_to_ctrack(h)))
+			goto out;
+
+	add_timer(&ct->timeout);
+	nf_conntrack_get(&ct->ct_general);
 	__nf_conntrack_hash_insert(ct, hash, repl_hash);
+	NF_CT_STAT_INC(net, insert);
+	spin_unlock_bh(&nf_conntrack_lock);
+
+	return 0;
+
+out:
+	NF_CT_STAT_INC(net, insert_failed);
+	spin_unlock_bh(&nf_conntrack_lock);
+	return -EEXIST;
 }
-EXPORT_SYMBOL_GPL(nf_conntrack_hash_insert);
+EXPORT_SYMBOL_GPL(nf_conntrack_hash_check_insert);
 
 /* Confirm a connection given skb; places it in hash table */
 int
diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index cc705175765c..30c9d4ca0218 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -1465,11 +1465,10 @@ ctnetlink_create_conntrack(struct net *net, u16 zone,
 	if (tstamp)
 		tstamp->start = ktime_to_ns(ktime_get_real());
 
-	add_timer(&ct->timeout);
-	spin_lock_bh(&nf_conntrack_lock);
-	nf_conntrack_hash_insert(ct);
-	nf_conntrack_get(&ct->ct_general);
-	spin_unlock_bh(&nf_conntrack_lock);
+	err = nf_conntrack_hash_check_insert(ct);
+	if (err < 0)
+		goto err2;
+
 	rcu_read_unlock();
 
 	return ct;
@@ -1511,12 +1510,10 @@ ctnetlink_new_conntrack(struct sock *ctnl, struct sk_buff *skb,
 			return err;
 	}
 
-	spin_lock_bh(&nf_conntrack_lock);
 	if (cda[CTA_TUPLE_ORIG])
 		h = nf_conntrack_find_get(net, zone, &otuple);
 	else if (cda[CTA_TUPLE_REPLY])
 		h = nf_conntrack_find_get(net, zone, &rtuple);
-	spin_unlock_bh(&nf_conntrack_lock);
 
 	if (h == NULL) {
 		err = -ENOENT;