Re: [PATCH 2/3] caif_virtio: fix the race between virtio_device_ready() and ndo_open()

From: Michael S. Tsirkin
Date: Mon Jun 20 2022 - 05:04:54 EST


On Mon, Jun 20, 2022 at 01:11:14PM +0800, Jason Wang wrote:
> We used to depend on the virtio_device_ready() that is called after

"We used to" implies it's not the case currently.
I think you mean "we currently depend".

> probe() by virtio_dev_probe() after netdev registration. This
> cause

causes

>a race between ndo_open() and virtio_device_ready(): if
> ndo_open() is called before virtio_device_ready(), the driver may
> start to use the device (e.g TX) before DRIVER_OK which violates the
> spec.
>
> Fixing this

Fix this

> by switching to use register_netdevice() and protect the
> virtio_device_ready() with rtnl_lock() to make sure ndo_open() can
> only be called after virtio_device_ready().
>
> Fixes: 0d2e1a2926b18 ("caif_virtio: Introduce caif over virtio")
> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>

Acked-by: Michael S. Tsirkin <mst@xxxxxxxxxx>

> ---
> drivers/net/caif/caif_virtio.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/caif/caif_virtio.c b/drivers/net/caif/caif_virtio.c
> index c677ded81133..66375bea2fcd 100644
> --- a/drivers/net/caif/caif_virtio.c
> +++ b/drivers/net/caif/caif_virtio.c
> @@ -719,13 +719,21 @@ static int cfv_probe(struct virtio_device *vdev)
> /* Carrier is off until netdevice is opened */
> netif_carrier_off(netdev);
>
> + /* serialize netdev register + virtio_device_ready() with ndo_open() */
> + rtnl_lock();
> +
> /* register Netdev */
> - err = register_netdev(netdev);
> + err = register_netdevice(netdev);
> if (err) {
> + rtnl_unlock();
> dev_err(&vdev->dev, "Unable to register netdev (%d)\n", err);
> goto err;
> }
>
> + virtio_device_ready(vdev);
> +
> + rtnl_unlock();
> +
> debugfs_init(cfv);
>
> return 0;
> --
> 2.25.1