1 files changed, 109 insertions, 90 deletions

diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index 2e86f520f799..ce3b316e2327 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -142,9 +142,28 @@ static inline struct l2tp_net *l2tp_pernet(const struct net *net)
 
 static void l2tp_tunnel_free(struct l2tp_tunnel *tunnel)
 {
+	struct sock *sk = tunnel->sock;
+
 	trace_free_tunnel(tunnel);
-	sock_put(tunnel->sock);
-	/* the tunnel is freed in the socket destructor */
+
+	if (sk) {
+		/* Disable udp encapsulation */
+		switch (tunnel->encap) {
+		case L2TP_ENCAPTYPE_UDP:
+			/* No longer an encapsulation socket. See net/ipv4/udp.c */
+			WRITE_ONCE(udp_sk(sk)->encap_type, 0);
+			udp_sk(sk)->encap_rcv = NULL;
+			udp_sk(sk)->encap_destroy = NULL;
+			break;
+		case L2TP_ENCAPTYPE_IP:
+			break;
+		}
+
+		tunnel->sock = NULL;
+		sock_put(sk);
+	}
+
+	kfree_rcu(tunnel, rcu);
 }
 
 static void l2tp_session_free(struct l2tp_session *session)
@@ -152,18 +171,29 @@ static void l2tp_session_free(struct l2tp_session *session)
 	trace_free_session(session);
 	if (session->tunnel)
 		l2tp_tunnel_dec_refcount(session->tunnel);
-	kfree(session);
+	kfree_rcu(session, rcu);
 }
 
-struct l2tp_tunnel *l2tp_sk_to_tunnel(struct sock *sk)
+struct l2tp_tunnel *l2tp_sk_to_tunnel(const struct sock *sk)
 {
-	struct l2tp_tunnel *tunnel = sk->sk_user_data;
+	const struct net *net = sock_net(sk);
+	unsigned long tunnel_id, tmp;
+	struct l2tp_tunnel *tunnel;
+	struct l2tp_net *pn;
 
-	if (tunnel)
-		if (WARN_ON(tunnel->magic != L2TP_TUNNEL_MAGIC))
-			return NULL;
+	rcu_read_lock_bh();
+	pn = l2tp_pernet(net);
+	idr_for_each_entry_ul(&pn->l2tp_tunnel_idr, tunnel, tmp, tunnel_id) {
+		if (tunnel &&
+		    tunnel->sock == sk &&
+		    refcount_inc_not_zero(&tunnel->ref_count)) {
+			rcu_read_unlock_bh();
+			return tunnel;
+		}
+	}
+	rcu_read_unlock_bh();
 
-	return tunnel;
+	return NULL;
 }
 EXPORT_SYMBOL_GPL(l2tp_sk_to_tunnel);
 
@@ -254,7 +284,14 @@ struct l2tp_session *l2tp_v3_session_get(const struct net *net, struct sock *sk,
 
 		hash_for_each_possible_rcu(pn->l2tp_v3_session_htable, session,
 					   hlist, key) {
-			if (session->tunnel->sock == sk &&
+			/* session->tunnel may be NULL if another thread is in
+			 * l2tp_session_register and has added an item to
+			 * l2tp_v3_session_htable but hasn't yet added the
+			 * session to its tunnel's session_list.
+			 */
+			struct l2tp_tunnel *tunnel = READ_ONCE(session->tunnel);
+
+			if (tunnel && tunnel->sock == sk &&
 			    refcount_inc_not_zero(&session->ref_count)) {
 				rcu_read_unlock_bh();
 				return session;
@@ -387,12 +424,12 @@ static int l2tp_session_collision_add(struct l2tp_net *pn,
 
 	/* If existing session isn't already in the session hlist, add it. */
 	if (!hash_hashed(&session2->hlist))
-		hash_add(pn->l2tp_v3_session_htable, &session2->hlist,
-			 session2->hlist_key);
+		hash_add_rcu(pn->l2tp_v3_session_htable, &session2->hlist,
+			     session2->hlist_key);
 
 	/* Add new session to the hlist and collision list */
-	hash_add(pn->l2tp_v3_session_htable, &session1->hlist,
-		 session1->hlist_key);
+	hash_add_rcu(pn->l2tp_v3_session_htable, &session1->hlist,
+		     session1->hlist_key);
 	refcount_inc(&clist->ref_count);
 	l2tp_session_coll_list_add(clist, session1);
 
@@ -408,7 +445,7 @@ static void l2tp_session_collision_del(struct l2tp_net *pn,
 
 	lockdep_assert_held(&pn->l2tp_session_idr_lock);
 
-	hash_del(&session->hlist);
+	hash_del_rcu(&session->hlist);
 
 	if (clist) {
 		/* Remove session from its collision list. If there
@@ -442,6 +479,7 @@ int l2tp_session_register(struct l2tp_session *session,
 {
 	struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
 	struct l2tp_session *other_session = NULL;
+	void *old = NULL;
 	u32 session_key;
 	int err;
 
@@ -482,15 +520,22 @@ int l2tp_session_register(struct l2tp_session *session,
 	}
 
 	l2tp_tunnel_inc_refcount(tunnel);
-	list_add(&session->list, &tunnel->session_list);
+	WRITE_ONCE(session->tunnel, tunnel);
+	list_add_rcu(&session->list, &tunnel->session_list);
 
+	/* this makes session available to lockless getters */
 	if (tunnel->version == L2TP_HDR_VER_3) {
 		if (!other_session)
-			idr_replace(&pn->l2tp_v3_session_idr, session, session_key);
+			old = idr_replace(&pn->l2tp_v3_session_idr, session, session_key);
 	} else {
-		idr_replace(&pn->l2tp_v2_session_idr, session, session_key);
+		old = idr_replace(&pn->l2tp_v2_session_idr, session, session_key);
 	}
 
+	/* old should be NULL, unless something removed or modified
+	 * the IDR entry after our idr_alloc_32 above (which shouldn't
+	 * happen).
+	 */
+	WARN_ON_ONCE(old);
 out:
 	spin_unlock_bh(&pn->l2tp_session_idr_lock);
 	spin_unlock_bh(&tunnel->list_lock);
@@ -797,7 +842,8 @@ void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
 		if (!session->lns_mode && !session->send_seq) {
 			trace_session_seqnum_lns_enable(session);
 			session->send_seq = 1;
-			l2tp_session_set_header_len(session, tunnel->version);
+			l2tp_session_set_header_len(session, tunnel->version,
+						    tunnel->encap);
 		}
 	} else {
 		/* No sequence numbers.
@@ -818,7 +864,8 @@ void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
 		if (!session->lns_mode && session->send_seq) {
 			trace_session_seqnum_lns_disable(session);
 			session->send_seq = 0;
-			l2tp_session_set_header_len(session, tunnel->version);
+			l2tp_session_set_header_len(session, tunnel->version,
+						    tunnel->encap);
 		} else if (session->send_seq) {
 			pr_debug_ratelimited("%s: recv data has no seq numbers when required. Discarding.\n",
 					     session->name);
@@ -1218,44 +1265,6 @@ EXPORT_SYMBOL_GPL(l2tp_xmit_skb);
  * Tinnel and session create/destroy.
  *****************************************************************************/
 
-/* Tunnel socket destruct hook.
- * The tunnel context is deleted only when all session sockets have been
- * closed.
- */
-static void l2tp_tunnel_destruct(struct sock *sk)
-{
-	struct l2tp_tunnel *tunnel = l2tp_sk_to_tunnel(sk);
-
-	if (!tunnel)
-		goto end;
-
-	/* Disable udp encapsulation */
-	switch (tunnel->encap) {
-	case L2TP_ENCAPTYPE_UDP:
-		/* No longer an encapsulation socket. See net/ipv4/udp.c */
-		WRITE_ONCE(udp_sk(sk)->encap_type, 0);
-		udp_sk(sk)->encap_rcv = NULL;
-		udp_sk(sk)->encap_destroy = NULL;
-		break;
-	case L2TP_ENCAPTYPE_IP:
-		break;
-	}
-
-	/* Remove hooks into tunnel socket */
-	write_lock_bh(&sk->sk_callback_lock);
-	sk->sk_destruct = tunnel->old_sk_destruct;
-	sk->sk_user_data = NULL;
-	write_unlock_bh(&sk->sk_callback_lock);
-
-	/* Call the original destructor */
-	if (sk->sk_destruct)
-		(*sk->sk_destruct)(sk);
-
-	kfree_rcu(tunnel, rcu);
-end:
-	return;
-}
-
 /* Remove an l2tp session from l2tp_core's lists. */
 static void l2tp_session_unhash(struct l2tp_session *session)
 {
@@ -1288,8 +1297,6 @@ static void l2tp_session_unhash(struct l2tp_session *session)
 
 		spin_unlock_bh(&pn->l2tp_session_idr_lock);
 		spin_unlock_bh(&tunnel->list_lock);
-
-		synchronize_rcu();
 	}
 }
 
@@ -1301,28 +1308,21 @@ static void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel)
 
 	spin_lock_bh(&tunnel->list_lock);
 	tunnel->acpt_newsess = false;
-	for (;;) {
-		session = list_first_entry_or_null(&tunnel->session_list,
-						   struct l2tp_session, list);
-		if (!session)
-			break;
-		l2tp_session_inc_refcount(session);
-		list_del_init(&session->list);
-		spin_unlock_bh(&tunnel->list_lock);
+	list_for_each_entry(session, &tunnel->session_list, list)
 		l2tp_session_delete(session);
-		spin_lock_bh(&tunnel->list_lock);
-		l2tp_session_dec_refcount(session);
-	}
 	spin_unlock_bh(&tunnel->list_lock);
 }
 
 /* Tunnel socket destroy hook for UDP encapsulation */
 static void l2tp_udp_encap_destroy(struct sock *sk)
 {
-	struct l2tp_tunnel *tunnel = l2tp_sk_to_tunnel(sk);
+	struct l2tp_tunnel *tunnel;
 
-	if (tunnel)
+	tunnel = l2tp_sk_to_tunnel(sk);
+	if (tunnel) {
 		l2tp_tunnel_delete(tunnel);
+		l2tp_tunnel_dec_refcount(tunnel);
+	}
 }
 
 static void l2tp_tunnel_remove(struct net *net, struct l2tp_tunnel *tunnel)
@@ -1505,7 +1505,6 @@ int l2tp_tunnel_create(int fd, int version, u32 tunnel_id, u32 peer_tunnel_id,
 	tunnel->tunnel_id = tunnel_id;
 	tunnel->peer_tunnel_id = peer_tunnel_id;
 
-	tunnel->magic = L2TP_TUNNEL_MAGIC;
 	sprintf(&tunnel->name[0], "tunl %u", tunnel_id);
 	spin_lock_init(&tunnel->list_lock);
 	tunnel->acpt_newsess = true;
@@ -1531,6 +1530,8 @@ EXPORT_SYMBOL_GPL(l2tp_tunnel_create);
 static int l2tp_validate_socket(const struct sock *sk, const struct net *net,
 				enum l2tp_encap_type encap)
 {
+	struct l2tp_tunnel *tunnel;
+
 	if (!net_eq(sock_net(sk), net))
 		return -EINVAL;
 
@@ -1544,8 +1545,11 @@ static int l2tp_validate_socket(const struct sock *sk, const struct net *net,
 	    (encap == L2TP_ENCAPTYPE_IP && sk->sk_protocol != IPPROTO_L2TP))
 		return -EPROTONOSUPPORT;
 
-	if (sk->sk_user_data)
+	tunnel = l2tp_sk_to_tunnel(sk);
+	if (tunnel) {
+		l2tp_tunnel_dec_refcount(tunnel);
 		return -EBUSY;
+	}
 
 	return 0;
 }
@@ -1584,12 +1588,10 @@ int l2tp_tunnel_register(struct l2tp_tunnel *tunnel, struct net *net,
 	ret = l2tp_validate_socket(sk, net, tunnel->encap);
 	if (ret < 0)
 		goto err_inval_sock;
-	rcu_assign_sk_user_data(sk, tunnel);
 	write_unlock_bh(&sk->sk_callback_lock);
 
 	if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
 		struct udp_tunnel_sock_cfg udp_cfg = {
-			.sk_user_data = tunnel,
 			.encap_type = UDP_ENCAP_L2TPINUDP,
 			.encap_rcv = l2tp_udp_encap_recv,
 			.encap_err_rcv = l2tp_udp_encap_err_recv,
@@ -1599,8 +1601,6 @@ int l2tp_tunnel_register(struct l2tp_tunnel *tunnel, struct net *net,
 		setup_udp_tunnel_sock(net, sock, &udp_cfg);
 	}
 
-	tunnel->old_sk_destruct = sk->sk_destruct;
-	sk->sk_destruct = &l2tp_tunnel_destruct;
 	sk->sk_allocation = GFP_ATOMIC;
 	release_sock(sk);
 
@@ -1647,23 +1647,37 @@ EXPORT_SYMBOL_GPL(l2tp_tunnel_delete);
 
 void l2tp_session_delete(struct l2tp_session *session)
 {
-	if (test_and_set_bit(0, &session->dead))
-		return;
+	if (!test_and_set_bit(0, &session->dead)) {
+		trace_delete_session(session);
+		l2tp_session_inc_refcount(session);
+		queue_work(l2tp_wq, &session->del_work);
+	}
+}
+EXPORT_SYMBOL_GPL(l2tp_session_delete);
+
+/* Workqueue session deletion function */
+static void l2tp_session_del_work(struct work_struct *work)
+{
+	struct l2tp_session *session = container_of(work, struct l2tp_session,
+						    del_work);
 
-	trace_delete_session(session);
 	l2tp_session_unhash(session);
 	l2tp_session_queue_purge(session);
 	if (session->session_close)
 		(*session->session_close)(session);
 
+	/* drop initial ref */
+	l2tp_session_dec_refcount(session);
+
+	/* drop workqueue ref */
 	l2tp_session_dec_refcount(session);
 }
-EXPORT_SYMBOL_GPL(l2tp_session_delete);
 
 /* We come here whenever a session's send_seq, cookie_len or
  * l2specific_type parameters are set.
  */
-void l2tp_session_set_header_len(struct l2tp_session *session, int version)
+void l2tp_session_set_header_len(struct l2tp_session *session, int version,
+				 enum l2tp_encap_type encap)
 {
 	if (version == L2TP_HDR_VER_2) {
 		session->hdr_len = 6;
@@ -1672,7 +1686,7 @@ void l2tp_session_set_header_len(struct l2tp_session *session, int version)
 	} else {
 		session->hdr_len = 4 + session->cookie_len;
 		session->hdr_len += l2tp_get_l2specific_len(session);
-		if (session->tunnel->encap == L2TP_ENCAPTYPE_UDP)
+		if (encap == L2TP_ENCAPTYPE_UDP)
 			session->hdr_len += 4;
 	}
 }
@@ -1686,7 +1700,6 @@ struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunn
 	session = kzalloc(sizeof(*session) + priv_size, GFP_KERNEL);
 	if (session) {
 		session->magic = L2TP_SESSION_MAGIC;
-		session->tunnel = tunnel;
 
 		session->session_id = session_id;
 		session->peer_session_id = peer_session_id;
@@ -1710,6 +1723,7 @@ struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunn
 		INIT_HLIST_NODE(&session->hlist);
 		INIT_LIST_HEAD(&session->clist);
 		INIT_LIST_HEAD(&session->list);
+		INIT_WORK(&session->del_work, l2tp_session_del_work);
 
 		if (cfg) {
 			session->pwtype = cfg->pw_type;
@@ -1724,7 +1738,7 @@ struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunn
 			memcpy(&session->peer_cookie[0], &cfg->peer_cookie[0], cfg->peer_cookie_len);
 		}
 
-		l2tp_session_set_header_len(session, tunnel->version);
+		l2tp_session_set_header_len(session, tunnel->version, tunnel->encap);
 
 		refcount_set(&session->ref_count, 1);
 
@@ -1753,7 +1767,7 @@ static __net_init int l2tp_init_net(struct net *net)
 	return 0;
 }
 
-static __net_exit void l2tp_exit_net(struct net *net)
+static __net_exit void l2tp_pre_exit_net(struct net *net)
 {
 	struct l2tp_net *pn = l2tp_pernet(net);
 	struct l2tp_tunnel *tunnel = NULL;
@@ -1767,8 +1781,12 @@ static __net_exit void l2tp_exit_net(struct net *net)
 	rcu_read_unlock_bh();
 
 	if (l2tp_wq)
-		flush_workqueue(l2tp_wq);
-	rcu_barrier();
+		drain_workqueue(l2tp_wq);
+}
+
+static __net_exit void l2tp_exit_net(struct net *net)
+{
+	struct l2tp_net *pn = l2tp_pernet(net);
 
 	idr_destroy(&pn->l2tp_v2_session_idr);
 	idr_destroy(&pn->l2tp_v3_session_idr);
@@ -1778,6 +1796,7 @@ static __net_exit void l2tp_exit_net(struct net *net)
 static struct pernet_operations l2tp_net_ops = {
 	.init = l2tp_init_net,
 	.exit = l2tp_exit_net,
+	.pre_exit = l2tp_pre_exit_net,
 	.id   = &l2tp_net_id,
 	.size = sizeof(struct l2tp_net),
 };