l2tp: ensure session can't get removed during pppol2tp_session_ioctl()

commit 57377d63547861919ee634b845c7caa38de4a452 upstream.

Holding a reference on session is required before calling
pppol2tp_session_ioctl(). The session could get freed while processing the
ioctl otherwise. Since pppol2tp_session_ioctl() uses the session's socket,
we also need to take a reference on it in l2tp_session_get().

Fixes: fd558d186df2 ("l2tp: Split pppol2tp patch into separate l2tp and ppp parts")
Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/l2tp/l2tp_ppp.c b/net/l2tp/l2tp_ppp.c
index 1387f54..c1c9a9e 100644 (file)
--- a/net/l2tp/l2tp_ppp.c
+++ b/net/l2tp/l2tp_ppp.c
@@ -1141,11 +1141,18 @@ 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