1 files changed, 120 insertions, 32 deletions

diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index 8adab6335ced..e927422d8c58 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -278,6 +278,55 @@ struct l2tp_session *l2tp_session_find(struct net *net, struct l2tp_tunnel *tunn
 }
 EXPORT_SYMBOL_GPL(l2tp_session_find);
 
+/* Like l2tp_session_find() but takes a reference on the returned session.
+ * Optionally calls session->ref() too if do_ref is true.
+ */
+struct l2tp_session *l2tp_session_get(struct net *net,
+				      struct l2tp_tunnel *tunnel,
+				      u32 session_id, bool do_ref)
+{
+	struct hlist_head *session_list;
+	struct l2tp_session *session;
+
+	if (!tunnel) {
+		struct l2tp_net *pn = l2tp_pernet(net);
+
+		session_list = l2tp_session_id_hash_2(pn, session_id);
+
+		rcu_read_lock_bh();
+		hlist_for_each_entry_rcu(session, session_list, global_hlist) {
+			if (session->session_id == session_id) {
+				l2tp_session_inc_refcount(session);
+				if (do_ref && session->ref)
+					session->ref(session);
+				rcu_read_unlock_bh();
+
+				return session;
+			}
+		}
+		rcu_read_unlock_bh();
+
+		return NULL;
+	}
+
+	session_list = l2tp_session_id_hash(tunnel, session_id);
+	read_lock_bh(&tunnel->hlist_lock);
+	hlist_for_each_entry(session, session_list, hlist) {
+		if (session->session_id == session_id) {
+			l2tp_session_inc_refcount(session);
+			if (do_ref && session->ref)
+				session->ref(session);
+			read_unlock_bh(&tunnel->hlist_lock);
+
+			return session;
+		}
+	}
+	read_unlock_bh(&tunnel->hlist_lock);
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(l2tp_session_get);
+
 struct l2tp_session *l2tp_session_find_nth(struct l2tp_tunnel *tunnel, int nth)
 {
 	int hash;
@@ -303,7 +352,8 @@ EXPORT_SYMBOL_GPL(l2tp_session_find_nth);
 /* Lookup a session by interface name.
  * This is very inefficient but is only used by management interfaces.
  */
-struct l2tp_session *l2tp_session_find_by_ifname(struct net *net, char *ifname)
+struct l2tp_session *l2tp_session_get_by_ifname(struct net *net, char *ifname,
+						bool do_ref)
 {
 	struct l2tp_net *pn = l2tp_pernet(net);
 	int hash;
@@ -313,7 +363,11 @@ struct l2tp_session *l2tp_session_find_by_ifname(struct net *net, char *ifname)
 	for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++) {
 		hlist_for_each_entry_rcu(session, &pn->l2tp_session_hlist[hash], global_hlist) {
 			if (!strcmp(session->ifname, ifname)) {
+				l2tp_session_inc_refcount(session);
+				if (do_ref && session->ref)
+					session->ref(session);
 				rcu_read_unlock_bh();
+
 				return session;
 			}
 		}
@@ -323,7 +377,49 @@ struct l2tp_session *l2tp_session_find_by_ifname(struct net *net, char *ifname)
 
 	return NULL;
 }
-EXPORT_SYMBOL_GPL(l2tp_session_find_by_ifname);
+EXPORT_SYMBOL_GPL(l2tp_session_get_by_ifname);
+
+static int l2tp_session_add_to_tunnel(struct l2tp_tunnel *tunnel,
+				      struct l2tp_session *session)
+{
+	struct l2tp_session *session_walk;
+	struct hlist_head *g_head;
+	struct hlist_head *head;
+	struct l2tp_net *pn;
+
+	head = l2tp_session_id_hash(tunnel, session->session_id);
+
+	write_lock_bh(&tunnel->hlist_lock);
+	hlist_for_each_entry(session_walk, head, hlist)
+		if (session_walk->session_id == session->session_id)
+			goto exist;
+
+	if (tunnel->version == L2TP_HDR_VER_3) {
+		pn = l2tp_pernet(tunnel->l2tp_net);
+		g_head = l2tp_session_id_hash_2(l2tp_pernet(tunnel->l2tp_net),
+						session->session_id);
+
+		spin_lock_bh(&pn->l2tp_session_hlist_lock);
+		hlist_for_each_entry(session_walk, g_head, global_hlist)
+			if (session_walk->session_id == session->session_id)
+				goto exist_glob;
+
+		hlist_add_head_rcu(&session->global_hlist, g_head);
+		spin_unlock_bh(&pn->l2tp_session_hlist_lock);
+	}
+
+	hlist_add_head(&session->hlist, head);
+	write_unlock_bh(&tunnel->hlist_lock);
+
+	return 0;
+
+exist_glob:
+	spin_unlock_bh(&pn->l2tp_session_hlist_lock);
+exist:
+	write_unlock_bh(&tunnel->hlist_lock);
+
+	return -EEXIST;
+}
 
 /* Lookup a tunnel by id
  */
@@ -633,6 +729,9 @@ discard:
  * a data (not control) frame before coming here. Fields up to the
  * session-id have already been parsed and ptr points to the data
  * after the session-id.
+ *
+ * session->ref() must have been called prior to l2tp_recv_common().
+ * session->deref() will be called automatically after skb is processed.
  */
 void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
 		      unsigned char *ptr, unsigned char *optr, u16 hdrflags,
@@ -642,14 +741,6 @@ void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
 	int offset;
 	u32 ns, nr;
 
-	/* The ref count is increased since we now hold a pointer to
-	 * the session. Take care to decrement the refcnt when exiting
-	 * this function from now on...
-	 */
-	l2tp_session_inc_refcount(session);
-	if (session->ref)
-		(*session->ref)(session);
-
 	/* Parse and check optional cookie */
 	if (session->peer_cookie_len > 0) {
 		if (memcmp(ptr, &session->peer_cookie[0], session->peer_cookie_len)) {
@@ -802,8 +893,6 @@ void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
 	/* Try to dequeue as many skbs from reorder_q as we can. */
 	l2tp_recv_dequeue(session);
 
-	l2tp_session_dec_refcount(session);
-
 	return;
 
 discard:
@@ -812,8 +901,6 @@ discard:
 
 	if (session->deref)
 		(*session->deref)(session);
-
-	l2tp_session_dec_refcount(session);
 }
 EXPORT_SYMBOL(l2tp_recv_common);
 
@@ -920,8 +1007,14 @@ static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb,
 	}
 
 	/* Find the session context */
-	session = l2tp_session_find(tunnel->l2tp_net, tunnel, session_id);
+	session = l2tp_session_get(tunnel->l2tp_net, tunnel, session_id, true);
 	if (!session || !session->recv_skb) {
+		if (session) {
+			if (session->deref)
+				session->deref(session);
+			l2tp_session_dec_refcount(session);
+		}
+
 		/* Not found? Pass to userspace to deal with */
 		l2tp_info(tunnel, L2TP_MSG_DATA,
 			  "%s: no session found (%u/%u). Passing up.\n",
@@ -930,6 +1023,7 @@ static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb,
 	}
 
 	l2tp_recv_common(session, skb, ptr, optr, hdrflags, length, payload_hook);
+	l2tp_session_dec_refcount(session);
 
 	return 0;
 
@@ -1738,6 +1832,7 @@ EXPORT_SYMBOL_GPL(l2tp_session_set_header_len);
 struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunnel, u32 session_id, u32 peer_session_id, struct l2tp_session_cfg *cfg)
 {
 	struct l2tp_session *session;
+	int err;
 
 	session = kzalloc(sizeof(struct l2tp_session) + priv_size, GFP_KERNEL);
 	if (session != NULL) {
@@ -1793,6 +1888,13 @@ struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunn
 
 		l2tp_session_set_header_len(session, tunnel->version);
 
+		err = l2tp_session_add_to_tunnel(tunnel, session);
+		if (err) {
+			kfree(session);
+
+			return ERR_PTR(err);
+		}
+
 		/* Bump the reference count. The session context is deleted
 		 * only when this drops to zero.
 		 */
@@ -1802,28 +1904,14 @@ struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunn
 		/* Ensure tunnel socket isn't deleted */
 		sock_hold(tunnel->sock);
 
-		/* Add session to the tunnel's hash list */
-		write_lock_bh(&tunnel->hlist_lock);
-		hlist_add_head(&session->hlist,
-			       l2tp_session_id_hash(tunnel, session_id));
-		write_unlock_bh(&tunnel->hlist_lock);
-
-		/* And to the global session list if L2TPv3 */
-		if (tunnel->version != L2TP_HDR_VER_2) {
-			struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
-
-			spin_lock_bh(&pn->l2tp_session_hlist_lock);
-			hlist_add_head_rcu(&session->global_hlist,
-					   l2tp_session_id_hash_2(pn, session_id));
-			spin_unlock_bh(&pn->l2tp_session_hlist_lock);
-		}
-
 		/* Ignore management session in session count value */
 		if (session->session_id != 0)
 			atomic_inc(&l2tp_session_count);
+
+		return session;
 	}
 
-	return session;
+	return ERR_PTR(-ENOMEM);
 }
 EXPORT_SYMBOL_GPL(l2tp_session_create);