[PATCH 5.10 094/104] net/vmw_vsock: fix NULL pointer dereference

[Greg Kroah-Hartman]

From: Norbert Slusarek <nslusarek@xxxxxxx>

commit 5d1cbcc990f18edaddddef26677073c4e6fad7b7 upstream.

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")
Signed-off-by: Norbert Slusarek <nslusarek@xxxxxxx>
Reviewed-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
Link: https://lore.kernel.org/r/trinity-c2d6cede-bfb1-44e2-85af-1fbc7f541715-1612535117028@3c-app-gmx-bap12
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/vmw_vsock/af_vsock.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -1216,7 +1216,7 @@ static int vsock_transport_cancel_pkt(st
 {
 	const struct vsock_transport *transport = vsk->transport;
 
-	if (!transport->cancel_pkt)
+	if (!transport || !transport->cancel_pkt)
 		return -EOPNOTSUPP;
 
 	return transport->cancel_pkt(vsk);