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Message-Id: <20200411115409.631912991@linuxfoundation.org>
Date: Sat, 11 Apr 2020 14:08:41 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Guillaume Nault <g.nault@...halink.fr>,
"David S. Miller" <davem@...emloft.net>,
Will Deacon <will@...nel.org>
Subject: [PATCH 4.4 11/29] l2tp: ensure sessions are freed after their PPPOL2TP socket
From: Guillaume Nault <g.nault@...halink.fr>
commit cdd10c9627496ad25c87ce6394e29752253c69d3 upstream.
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@...halink.fr>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Will Deacon <will@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
net/l2tp/l2tp_ppp.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
--- a/net/l2tp/l2tp_ppp.c
+++ b/net/l2tp/l2tp_ppp.c
@@ -452,11 +452,11 @@ static void pppol2tp_session_close(struc
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
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