netdev - Re: [PATCH] vhost/vsock: accept only packets with the right dst

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Date:   Tue, 10 Dec 2019 09:05:58 -0500
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Stefano Garzarella <sgarzare@...hat.com>
Cc:     virtualization@...ts.linux-foundation.org,
        Stefan Hajnoczi <stefanha@...hat.com>,
        Jason Wang <jasowang@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH] vhost/vsock: accept only packets with the right dst_cid

On Fri, Dec 06, 2019 at 03:39:12PM +0100, Stefano Garzarella wrote:
> When we receive a new packet from the guest, we check if the
> src_cid is correct, but we forgot to check the dst_cid.
> 
> The host should accept only packets where dst_cid is
> equal to the host CID.
> 
> Signed-off-by: Stefano Garzarella <sgarzare@...hat.com>

what's the implication of processing incorrect dst cid?
I think mostly it's malformed guests, right?
Everyone else just passes the known host cid ...

> ---
>  drivers/vhost/vsock.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
> index 50de0642dea6..c2d7d57e98cf 100644
> --- a/drivers/vhost/vsock.c
> +++ b/drivers/vhost/vsock.c
> @@ -480,7 +480,9 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
>  		virtio_transport_deliver_tap_pkt(pkt);
>  
>  		/* Only accept correctly addressed packets */
> -		if (le64_to_cpu(pkt->hdr.src_cid) == vsock->guest_cid)
> +		if (le64_to_cpu(pkt->hdr.src_cid) == vsock->guest_cid &&
> +		    le64_to_cpu(pkt->hdr.dst_cid) ==
> +		    vhost_transport_get_local_cid())
>  			virtio_transport_recv_pkt(&vhost_transport, pkt);
>  		else
>  			virtio_transport_free_pkt(pkt);
> -- 
> 2.23.0