[PATCH net] l2tp: check ps->sock before running pppol2tp_session_ioctl()

[Guillaume Nault]

When pppol2tp_session_ioctl() is called by pppol2tp_tunnel_ioctl(),
the session may be unconnected. That is, it was created by
pppol2tp_session_create() and hasn't been connected with
pppol2tp_connect(). In this case, ps->sock is NULL, so we need to check
for this case in order to avoid dereferencing a NULL pointer.

Fixes: 309795f4bec2 ("l2tp: Add netlink control API for L2TP")
Signed-off-by: Guillaume Nault <g.na...@alphalink.fr>
---
 net/l2tp/l2tp_ppp.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/l2tp/l2tp_ppp.c b/net/l2tp/l2tp_ppp.c
index bc6e8bfc5be4..f50452b919d5 100644
--- a/net/l2tp/l2tp_ppp.c
+++ b/net/l2tp/l2tp_ppp.c
@@ -988,6 +988,9 @@ static int pppol2tp_session_ioctl(struct l2tp_session 
*session,
                 session->name, cmd, arg);
 
        sk = ps->sock;
+       if (!sk)
+               return -EBADR;
+
        sock_hold(sk);
 
        switch (cmd) {
-- 
2.15.0.rc0