Re: [PATCH net v2 1/5] vsock/virtio: discard packets if the transport changes

[Hyunwoo Kim]

On Fri, Jan 10, 2025 at 09:35:07AM +0100, Stefano Garzarella wrote:
> 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")
> Cc: stable@xxxxxxxxxxxxxxx
> Reported-by: Hyunwoo Kim <v4bel@xxxxxxxxx>
> Reported-by: Wongi Lee <qwerty@xxxxxxxxx>
> Closes: https://lore.kernel.org/netdev/Z2LvdTTQR7dBmPb5@v4bel-B760M-AORUS-ELITE-AX/
> Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
> ---
>  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
> 

Reviewed-by: Hyunwoo Kim <v4bel@xxxxxxxxx>


Regards,
Hyunwoo Kim