[PATCH 4.9 046/172] l2tp: ensure session cant get removed during pppol2tp_session_ioctl()

Greg Kroah-Hartman
2017-07-03T13:43:42Z

From: Guillaume Nault <g.nault@alphalink.fr>

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>

---
net/l2tp/l2tp_ppp.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)

--- a/net/l2tp/l2tp_ppp.c
+++ b/net/l2tp/l2tp_ppp.c
@@ -1141,11 +1141,18 @@ static int pppol2tp_tunnel_ioctl(struct
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