l2tp_session_find() doesn't take any reference on the returned session.
Therefore, the session may disappear while sending the notification.
Use l2tp_session_get() instead and decrement session's refcount once
the notification is sent.
Fixes: 33f72e6f0c ("l2tp : multicast notification to the registered listeners")
Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
5e6a9e5a35