On Tue, Mar 22, 2022 at 11:38:23AM +0100, Stefano Garzarella wrote:
> virtio spec requires drivers to set DRIVER_OK before using VQs.
> This is set automatically after probe returns, but virtio-vsock
> driver uses VQs in the probe function to fill rx and event VQs
> with new buffers.
So this is a spec violation. absolutely.
> Let's fix this, calling virtio_device_ready() before using VQs
> in the probe function.
>
> Fixes: 0ea9e1d3a9e3 ("VSOCK: Introduce virtio_transport.ko")
> Signed-off-by: Stefano Garzarella <sgarz...@redhat.com>
> ---
> net/vmw_vsock/virtio_transport.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/net/vmw_vsock/virtio_transport.c
> b/net/vmw_vsock/virtio_transport.c
> index 5afc194a58bb..b1962f8cd502 100644
> --- a/net/vmw_vsock/virtio_transport.c
> +++ b/net/vmw_vsock/virtio_transport.c
> @@ -622,6 +622,8 @@ static int virtio_vsock_probe(struct virtio_device *vdev)
> INIT_WORK(&vsock->event_work, virtio_transport_event_work);
> INIT_WORK(&vsock->send_pkt_work, virtio_transport_send_pkt_work);
>
> + virtio_device_ready(vdev);
> +
> mutex_lock(&vsock->tx_lock);
> vsock->tx_run = true;
> mutex_unlock(&vsock->tx_lock);
Here's the whole code snippet:
mutex_lock(&vsock->tx_lock);
vsock->tx_run = true;
mutex_unlock(&vsock->tx_lock);
mutex_lock(&vsock->rx_lock);
virtio_vsock_rx_fill(vsock);
vsock->rx_run = true;
mutex_unlock(&vsock->rx_lock);
mutex_lock(&vsock->event_lock);
virtio_vsock_event_fill(vsock);
vsock->event_run = true;
mutex_unlock(&vsock->event_lock);
if (virtio_has_feature(vdev, VIRTIO_VSOCK_F_SEQPACKET))
vsock->seqpacket_allow = true;
vdev->priv = vsock;
rcu_assign_pointer(the_virtio_vsock, vsock);
mutex_unlock(&the_virtio_vsock_mutex);
I worry that this is not the only problem here:
seqpacket_allow and setting of vdev->priv at least after
device is active look suspicious.
E.g.:
static void virtio_vsock_event_done(struct virtqueue *vq)
{
struct virtio_vsock *vsock = vq->vdev->priv;
if (!vsock)
return;
queue_work(virtio_vsock_workqueue, &vsock->event_work);
}
looks like it will miss events now they will be reported earlier.
One might say that since vq has been kicked it might send
interrupts earlier too so not a new problem, but
there's a chance device actually waits until DRIVER_OK
to start operating.
> --
> 2.35.1
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