On Mon, 22 Nov 2021 17:35:24 +0100
Stefano Garzarella <sgarzare@xxxxxxxxxx> wrote:
> The "used length" reported by calling vhost_add_used() must be the
> number of bytes written by the device (using "in" buffers).
>
> In vhost_vsock_handle_tx_kick() the device only reads the guest
> buffers (they are all "out" buffers), without writing anything,
> so we must pass 0 as "used length" to comply virtio spec.
>
> Fixes: 433fc58e6bf2 ("VSOCK: Introduce vhost_vsock.ko")
> Cc: stable@xxxxxxxxxxxxxxx
> Reported-by: Halil Pasic <pasic@xxxxxxxxxxxxx>
> Suggested-by: Jason Wang <jasowang@xxxxxxxxxx>
> Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
Reviewed-by: Halil Pasic <pasic@xxxxxxxxxxxxx>
> ---
> drivers/vhost/vsock.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
> index 938aefbc75ec..4e3b95af7ee4 100644
> --- a/drivers/vhost/vsock.c
> +++ b/drivers/vhost/vsock.c
> @@ -554,7 +554,7 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
> virtio_transport_free_pkt(pkt);
>
> len += sizeof(pkt->hdr);
> - vhost_add_used(vq, head, len);
> + vhost_add_used(vq, head, 0);
> total_len += len;
> added = true;
> } while(likely(!vhost_exceeds_weight(vq, ++pkts, total_len)));
