Re: [PATCH net-next v18 08/13] ax88179_178a: Add AX179A/AX279 multicast configuration

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] net: ax88179_set_multicast() data race on data->rxctl
--

commit 547e4ec41af3f2201955124dd2564e630771c80f
Author: Birger Koblitz <mail@birger-koblitz.de>

ax88179_178a: Add AX179A/AX279 multicast configuration

This commit adds support for conditionally setting the AX_RX_CTL_IPE flag
in AX_RX_CTL based on ip_align. It also ensures AX_RX_CTL_DROPCRCERR is
set to match the initial configuration in ax88179_reset().

> diff --git a/drivers/net/usb/ax88179_lib.c b/drivers/net/usb/ax88179_lib.c
> index 0efc2eb95e4b3..ea19700c8230f 100644
> --- a/drivers/net/usb/ax88179_lib.c
> +++ b/drivers/net/usb/ax88179_lib.c
> @@ -321,10 +321,14 @@ int ax88179_set_eeprom(struct net_device *net, struct ethtool_eeprom *eeprom, u8
>  void ax88179_set_multicast(struct net_device *net)
>  {
>  	struct usbnet *dev = netdev_priv(net);
> -	struct ax88179_data *data = dev->driver_priv;
>  	u8 *m_filter = ((u8 *)dev->data);
> +	struct ax88179_data *data;
> +
> +	data = dev->driver_priv;
>  
> -	data->rxctl = (AX_RX_CTL_START | AX_RX_CTL_AB | AX_RX_CTL_IPE);
> +	data->rxctl = (AX_RX_CTL_START | AX_RX_CTL_AB | AX_RX_CTL_DROPCRCERR);
> +	if (data->ip_align)
> +		data->rxctl |= AX_RX_CTL_IPE;

[Severity: High]
Does this non-atomic modification of data->rxctl introduce a data race?

It appears data->rxctl is updated here without lock synchronization. If
ax88179a_mac_link_up() is executing concurrently, could it fetch an
intermediate torn state?

For example, a concurrent reader might observe the state like this:

ax88179a_mac_link_up()
   ax88179_write_u16(dev, AX_ACCESS_MAC, AX_RX_CTL, 2, READ_ONCE(ax179_data->rxctl));

Could this result in corrupting the hardware register by committing a
partially updated rxctl state to the device?

>  
>  	if (net->flags & IFF_PROMISC) {
>  		data->rxctl |= AX_RX_CTL_PRO;

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261008-ax88179a-v18-0-6fa1d4c40422@birger-koblitz.de?part=8