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l2tp: ensure sessions are freed after their PPPOL2TP socket

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If l2tp_tunnel_delete() or l2tp_tunnel_closeall() deletes a session
right after pppol2tp_release() orphaned its socket, then the 'sock'
variable of the pppol2tp_session_close() callback is NULL. Yet the
session is still used by pppol2tp_release().

Therefore we need to take an extra reference in any case, to prevent
l2tp_tunnel_delete() or l2tp_tunnel_closeall() from freeing the session.

Since the pppol2tp_session_close() callback is only set if the session
is associated to a PPPOL2TP socket and that both l2tp_tunnel_delete()
and l2tp_tunnel_closeall() hold the PPPOL2TP socket before calling
pppol2tp_session_close(), we're sure that pppol2tp_session_close() and
pppol2tp_session_destruct() are paired and called in the right order.
So the reference taken by the former will be released by the later.

Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Guillaume Nault 2017-09-22 15:39:23 +02:00 committed by David S. Miller
parent 5c346525d3
commit cdd10c9627
1 changed files with 4 additions and 4 deletions
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8
net/l2tp/l2tp_ppp.c
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@ -437,11 +437,11 @@ static void pppol2tp_session_close(struct l2tp_session *session)
BUG_ON(session->magic != L2TP_SESSION_MAGIC);
if (sock) {
if (sock)
inet_shutdown(sock, SEND_SHUTDOWN);
/* Don't let the session go away before our socket does */
l2tp_session_inc_refcount(session);
}
/* Don't let the session go away before our socket does */
l2tp_session_inc_refcount(session);
}
/* Really kill the session socket. (Called from sock_put() if