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From:   Martin Schiller <ms@dev.tdt.de>
To:     andrew.hendry@gmail.com, davem@davemloft.net, kuba@kernel.org,
        edumazet@google.com, xiyuyang19@fudan.edu.cn
Cc:     linux-x25@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, Martin Schiller <ms@dev.tdt.de>
Subject: [RESEND PATCH v2] net/x25: Fix null-ptr-deref in x25_connect
Date:   Mon,  9 Nov 2020 07:54:49 +0100
Message-ID: <20201109065449.9014-1-ms@dev.tdt.de>
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This fixes a regression for blocking connects introduced by commit
4becb7ee5b3d ("net/x25: Fix x25_neigh refcnt leak when x25 disconnect").

The x25->neighbour is already set to "NULL" by x25_disconnect() now,
while a blocking connect is waiting in
x25_wait_for_connection_establishment(). Therefore x25->neighbour must
not be accessed here again and x25->state is also already set to
X25_STATE_0 by x25_disconnect().

Fixes: 4becb7ee5b3d ("net/x25: Fix x25_neigh refcnt leak when x25 disconn=
ect")
Signed-off-by: Martin Schiller <ms@dev.tdt.de>
---

Change from v1:
also handle interrupting signals correctly

---
 net/x25/af_x25.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c
index 0bbb283f23c9..046d3fee66a9 100644
--- a/net/x25/af_x25.c
+++ b/net/x25/af_x25.c
@@ -825,7 +825,7 @@ static int x25_connect(struct socket *sock, struct so=
ckaddr *uaddr,
 	sock->state =3D SS_CONNECTED;
 	rc =3D 0;
 out_put_neigh:
-	if (rc) {
+	if (rc && x25->neighbour) {
 		read_lock_bh(&x25_list_lock);
 		x25_neigh_put(x25->neighbour);
 		x25->neighbour =3D NULL;
--=20
2.20.1