l2tp: fix duplicate session creation

[mirror_ubuntu-bionic-kernel.git] / net / l2tp / l2tp_ppp.c

diff --git a/net/l2tp/l2tp_ppp.c b/net/l2tp/l2tp_ppp.c
index 36cc56fd041871c73796cc0a52241ef3e38483c9..26501902d1a7feaca1e3d5ce89419ea4c4801e4a 100644 (file)
--- a/net/l2tp/l2tp_ppp.c
+++ b/net/l2tp/l2tp_ppp.c
@@ -450,6 +450,10 @@ static void pppol2tp_session_close(struct l2tp_session *session)
 static void pppol2tp_session_destruct(struct sock *sk)
 {
        struct l2tp_session *session = sk->sk_user_data;
+
+       skb_queue_purge(&sk->sk_receive_queue);
+       skb_queue_purge(&sk->sk_write_queue);
+
        if (session) {
                sk->sk_user_data = NULL;
                BUG_ON(session->magic != L2TP_SESSION_MAGIC);
@@ -488,9 +492,6 @@ static int pppol2tp_release(struct socket *sock)
                l2tp_session_queue_purge(session);
                sock_put(sk);
        }
-       skb_queue_purge(&sk->sk_receive_queue);
-       skb_queue_purge(&sk->sk_write_queue);
-
        release_sock(sk);
 
        /* This will delete the session context via
@@ -582,6 +583,7 @@ static int pppol2tp_connect(struct socket *sock, struct sockaddr *uservaddr,
        int error = 0;
        u32 tunnel_id, peer_tunnel_id;
        u32 session_id, peer_session_id;
+       bool drop_refcnt = false;
        int ver = 2;
        int fd;
 
@@ -683,36 +685,36 @@ static int pppol2tp_connect(struct socket *sock, struct sockaddr *uservaddr,
        if (tunnel->peer_tunnel_id == 0)
                tunnel->peer_tunnel_id = peer_tunnel_id;
 
-       /* Create session if it doesn't already exist. We handle the
-        * case where a session was previously created by the netlink
-        * interface by checking that the session doesn't already have
-        * a socket and its tunnel socket are what we expect. If any
-        * of those checks fail, return EEXIST to the caller.
-        */
-       session = l2tp_session_find(sock_net(sk), tunnel, session_id);
-       if (session == NULL) {
-               /* Default MTU must allow space for UDP/L2TP/PPP
-                * headers.
+       session = l2tp_session_get(sock_net(sk), tunnel, session_id, false);
+       if (session) {
+               drop_refcnt = true;
+               ps = l2tp_session_priv(session);
+
+               /* Using a pre-existing session is fine as long as it hasn't
+                * been connected yet.
                 */
-               cfg.mtu = cfg.mru = 1500 - PPPOL2TP_HEADER_OVERHEAD;
+               if (ps->sock) {
+                       error = -EEXIST;
+                       goto end;
+               }
 
-               /* Allocate and initialize a new session context. */
-               session = l2tp_session_create(sizeof(struct pppol2tp_session),
-                                             tunnel, session_id,
-                                             peer_session_id, &cfg);
-               if (session == NULL) {
-                       error = -ENOMEM;
+               /* consistency checks */
+               if (ps->tunnel_sock != tunnel->sock) {
+                       error = -EEXIST;
                        goto end;
                }
        } else {
-               ps = l2tp_session_priv(session);
-               error = -EEXIST;
-               if (ps->sock != NULL)
-                       goto end;
+               /* Default MTU must allow space for UDP/L2TP/PPP headers */
+               cfg.mtu = 1500 - PPPOL2TP_HEADER_OVERHEAD;
+               cfg.mru = cfg.mtu;
 
-               /* consistency checks */
-               if (ps->tunnel_sock != tunnel->sock)
+               session = l2tp_session_create(sizeof(struct pppol2tp_session),
+                                             tunnel, session_id,
+                                             peer_session_id, &cfg);
+               if (IS_ERR(session)) {
+                       error = PTR_ERR(session);
                        goto end;
+               }
        }
 
        /* Associate session with its PPPoL2TP socket */
@@ -777,6 +779,8 @@ out_no_ppp:
                  session->name);
 
 end:
+       if (drop_refcnt)
+               l2tp_session_dec_refcount(session);
        release_sock(sk);
 
        return error;
@@ -804,12 +808,6 @@ static int pppol2tp_session_create(struct net *net, u32 tunnel_id, u32 session_i
        if (tunnel->sock == NULL)
                goto out;
 
-       /* Check that this session doesn't already exist */
-       error = -EEXIST;
-       session = l2tp_session_find(net, tunnel, session_id);
-       if (session != NULL)
-               goto out;
-
        /* Default MTU values. */
        if (cfg->mtu == 0)
                cfg->mtu = 1500 - PPPOL2TP_HEADER_OVERHEAD;
@@ -817,12 +815,13 @@ static int pppol2tp_session_create(struct net *net, u32 tunnel_id, u32 session_i
                cfg->mru = cfg->mtu;
 
        /* Allocate and initialize a new session context. */
-       error = -ENOMEM;
        session = l2tp_session_create(sizeof(struct pppol2tp_session),
                                      tunnel, session_id,
                                      peer_session_id, cfg);
-       if (session == NULL)
+       if (IS_ERR(session)) {
+               error = PTR_ERR(session);
                goto out;
+       }
 
        ps = l2tp_session_priv(session);
        ps->tunnel_sock = tunnel->sock;
@@ -1140,11 +1139,18 @@ static int pppol2tp_tunnel_ioctl(struct l2tp_tunnel *tunnel,
                if (stats.session_id != 0) {
                        /* resend to session ioctl handler */
                        struct l2tp_session *session =
-                               l2tp_session_find(sock_net(sk), tunnel, stats.session_id);
-                       if (session != NULL)
-                               err = pppol2tp_session_ioctl(session, cmd, arg);
-                       else
+                               l2tp_session_get(sock_net(sk), tunnel,
+                                                stats.session_id, true);
+
+                       if (session) {
+                               err = pppol2tp_session_ioctl(session, cmd,
+                                                            arg);
+                               if (session->deref)
+                                       session->deref(session);
+                               l2tp_session_dec_refcount(session);
+                       } else {
                                err = -EBADR;
+                       }
                        break;
                }
 #ifdef CONFIG_XFRM