netdev - Re: [PATCH net-next] net: virtio: use eth_hw_addr

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Date:   Wed, 27 Oct 2021 06:26:40 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org, jasowang@...hat.com,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH net-next] net: virtio: use eth_hw_addr_set()

On Wed, 27 Oct 2021 03:23:17 -0400 Michael S. Tsirkin wrote:
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index c501b5974aee..b7f35aff8e82 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -3177,12 +3177,16 @@ static int virtnet_probe(struct virtio_device *vdev)
> >  	dev->max_mtu = MAX_MTU;
> >  
> >  	/* Configuration may specify what MAC to use.  Otherwise random. */
> > -	if (virtio_has_feature(vdev, VIRTIO_NET_F_MAC))
> > +	if (virtio_has_feature(vdev, VIRTIO_NET_F_MAC)) {
> > +		u8 addr[MAX_ADDR_LEN];
> > +
> >  		virtio_cread_bytes(vdev,
> >  				   offsetof(struct virtio_net_config, mac),
> > -				   dev->dev_addr, dev->addr_len);
> > -	else
> > +				   addr, dev->addr_len);  
> 
> Maybe BUG_ON(dev->addr_len > sizeof addr);
> 
> here just to make sure we don't overflow addr silently?

Since I need to post a v2 and we're talking... can I just use
eth_hw_addr_set() instead? AFAICT netdev is always allocated with 
alloc_etherdev_mq() and ->addr_len never changed. Plus there is 
a number of Ethernet address helpers used so ETH_ALEN is kind of 
already assumed.

> > +		dev_addr_set(dev, addr);
> > +	} else {
> >  		eth_hw_addr_random(dev);
> > +	}
> >  
> >  	/* Set up our device-specific information */
> >  	vi = netdev_priv(dev);