linux-kernel - [PATCH v2] net/x25: Fix null-ptr-deref in x25

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Message-ID: <20201006054558.19453-1-ms@dev.tdt.de>
Date:   Tue,  6 Oct 2020 07:45:57 +0200
From:   Martin Schiller <ms@....tdt.de>
To:     andrew.hendry@...il.com, davem@...emloft.net, kuba@...nel.org,
        edumazet@...gle.com, xiyuyang19@...an.edu.cn
Cc:     linux-x25@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Martin Schiller <ms@....tdt.de>
Subject: [PATCH v2] net/x25: Fix null-ptr-deref in x25_connect

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 disconnect")
Signed-off-by: Martin Schiller <ms@....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 sockaddr *uaddr,
 	sock->state = SS_CONNECTED;
 	rc = 0;
 out_put_neigh:
-	if (rc) {
+	if (rc && x25->neighbour) {
 		read_lock_bh(&x25_list_lock);
 		x25_neigh_put(x25->neighbour);
 		x25->neighbour = NULL;
-- 
2.20.1