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

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Date:   Mon, 20 Jun 2022 05:04:36 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        davem@...emloft.net, kuba@...nel.org, erwan.yvin@...ricsson.com
Subject: Re: [PATCH 2/3] caif_virtio: fix the race between
 virtio_device_ready() and ndo_open()

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@...hat.com>

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

> ---
>  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