From: Will Deacon <will@kernel.org>
To: gregkh@linuxfoundation.org
Cc: stable@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel-team@android.com, g.nault@alphalink.fr,
"David S . Miller" <davem@davemloft.net>,
Will Deacon <will@kernel.org>
Subject: [PATCH 1/2] l2tp: ensure sessions are freed after their PPPOL2TP socket
Date: Thu, 2 Apr 2020 18:31:57 +0100 [thread overview]
Message-ID: <20200402173158.7798-2-will@kernel.org> (raw)
In-Reply-To: <20200402173158.7798-1-will@kernel.org>
From: Guillaume Nault <g.nault@alphalink.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@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Will Deacon <will@kernel.org>
---
net/l2tp/l2tp_ppp.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/net/l2tp/l2tp_ppp.c b/net/l2tp/l2tp_ppp.c
index 16b63e60396f..d919b3e6b548 100644
--- a/net/l2tp/l2tp_ppp.c
+++ b/net/l2tp/l2tp_ppp.c
@@ -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
--
2.26.0.rc2.310.g2932bb562d-goog
next prev parent reply other threads:[~2020-04-02 17:32 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-02 17:31 [PATCH 0/2] [backports] l2tp use-after-free fixes for 4.9 stable Will Deacon
2020-04-02 17:31 ` Will Deacon [this message]
2020-04-02 19:59 ` [PATCH 1/2] l2tp: ensure sessions are freed after their PPPOL2TP socket David Miller
2020-04-03 7:03 ` Will Deacon
2020-04-02 17:31 ` [PATCH 2/2] l2tp: fix race between l2tp_session_delete() and l2tp_tunnel_closeall() Will Deacon
2020-04-02 18:45 ` [PATCH 0/2] [backports] l2tp use-after-free fixes for 4.9 stable Greg KH
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