netdev - [PATCH] net/vmw_vsock: fix NULL pointer dereference

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Date:   Fri, 5 Feb 2021 15:25:17 +0100
From:   Norbert Slusarek <nslusarek@....net>
To:     sgarzare@...hat.com, alex.popov@...ux.com, eric.dumazet@...il.com
Cc:     netdev@...r.kernel.org
Subject: [PATCH] net/vmw_vsock: fix NULL pointer dereference

From: Norbert Slusarek <nslusarek@....net>
Date: Fri, 5 Feb 2021 13:12:06 +0100
Subject: [PATCH] net/vmw_vsock: fix NULL pointer dereference

In vsock_stream_connect(), a thread will enter schedule_timeout().
While being scheduled out, another thread can enter vsock_stream_connect()
as well and set vsk->transport to NULL. In case a signal was sent, the
first thread can leave schedule_timeout() and vsock_transport_cancel_pkt()
will be called right after. Inside vsock_transport_cancel_pkt(), a null
dereference will happen on transport->cancel_pkt.

Fixes: c0cfa2d8a788 ("vsock: add multi-transports support")
Reported-by: Norbert Slusarek <nslusarek@....net>
Signed-off-by: Norbert Slusarek <nslusarek@....net>
---
 net/vmw_vsock/af_vsock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index 6894f21dc147..cb81cfb47a78 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -1233,7 +1233,7 @@ static int vsock_transport_cancel_pkt(struct vsock_sock *vsk)
 {
 	const struct vsock_transport *transport = vsk->transport;

-	if (!transport->cancel_pkt)
+	if (!transport || !transport->cancel_pkt)
 		return -EOPNOTSUPP;

 	return transport->cancel_pkt(vsk);
--
2.30.0