netdev - [PATCH net 1/2] vsock/virtio: discard packets if the transport changes

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Message-ID: <20250108180617.154053-2-sgarzare@redhat.com>
Date: Wed,  8 Jan 2025 19:06:16 +0100
From: Stefano Garzarella <sgarzare@...hat.com>
To: netdev@...r.kernel.org
Cc: Simon Horman <horms@...nel.org>,
	Stefan Hajnoczi <stefanha@...hat.com>,
	linux-kernel@...r.kernel.org,
	Eric Dumazet <edumazet@...gle.com>,
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
	Wongi Lee <qwerty@...ori.io>,
	"David S. Miller" <davem@...emloft.net>,
	Paolo Abeni <pabeni@...hat.com>,
	Jason Wang <jasowang@...hat.com>,
	Bobby Eshleman <bobby.eshleman@...edance.com>,
	virtualization@...ts.linux.dev,
	Eugenio Pérez <eperezma@...hat.com>,
	Stefano Garzarella <sgarzare@...hat.com>,
	Luigi Leonardi <leonardi@...hat.com>,
	bpf@...r.kernel.org,
	Jakub Kicinski <kuba@...nel.org>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Hyunwoo Kim <v4bel@...ori.io>,
	Michal Luczaj <mhal@...x.co>,
	kvm@...r.kernel.org
Subject: [PATCH net 1/2] vsock/virtio: discard packets if the transport changes

If the socket has been de-assigned or assigned to another transport,
we must discard any packets received because they are not expected
and would cause issues when we access vsk->transport.

A possible scenario is described by Hyunwoo Kim in the attached link,
where after a first connect() interrupted by a signal, and a second
connect() failed, we can find `vsk->transport` at NULL, leading to a
NULL pointer dereference.

Fixes: c0cfa2d8a788 ("vsock: add multi-transports support")
Reported-by: Hyunwoo Kim <v4bel@...ori.io>
Reported-by: Wongi Lee <qwerty@...ori.io>
Closes: https://lore.kernel.org/netdev/Z2LvdTTQR7dBmPb5@v4bel-B760M-AORUS-ELITE-AX/
Signed-off-by: Stefano Garzarella <sgarzare@...hat.com>
---
 net/vmw_vsock/virtio_transport_common.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 9acc13ab3f82..51a494b69be8 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -1628,8 +1628,11 @@ void virtio_transport_recv_pkt(struct virtio_transport *t,
 
 	lock_sock(sk);
 
-	/* Check if sk has been closed before lock_sock */
-	if (sock_flag(sk, SOCK_DONE)) {
+	/* Check if sk has been closed or assigned to another transport before
+	 * lock_sock (note: listener sockets are not assigned to any transport)
+	 */
+	if (sock_flag(sk, SOCK_DONE) ||
+	    (sk->sk_state != TCP_LISTEN && vsk->transport != &t->transport)) {
 		(void)virtio_transport_reset_no_sock(t, skb);
 		release_sock(sk);
 		sock_put(sk);
-- 
2.47.1