Re: [PATCH net-next v8 6/9] net: mdio: realtek-rtl9300: Add page tracking

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Data race on `priv->page[port]` due to missing `priv->lock` in `otto_emdio_notify_phy_detach`.
--

--- Patch [6]: [PATCH net-next v8 6/9] net: mdio: realtek-rtl9300: Add page tracking ---
commit 05ca21acb226d57fd7de64847d2a32c8443b9dcd
Author: Markus Stockhausen <markus.stockhausen@gmx.de>
net: mdio: realtek-rtl9300: Add page tracking

This commit intercepts accesses to the Realtek page register (C22 reg 31)
to prevent interference with the hardware polling unit. It stores the target
page per-port and injects it into hardware commands. It also restricts C22
bus attachment to Realtek PHYs and resets the cached page upon detach.

> diff --git a/drivers/net/mdio/mdio-realtek-rtl9300.c b/drivers/net/mdio/mdio-realtek-rtl9300.c
> index aca0a9448bb0c..dc3661b2cd945 100644
> --- a/drivers/net/mdio/mdio-realtek-rtl9300.c
> +++ b/drivers/net/mdio/mdio-realtek-rtl9300.c

[ ... ]

> @@ -608,12 +632,17 @@ static void otto_emdio_notify_phy_detach(struct phy_device *phydev)
>  {
>  	struct otto_emdio_priv *priv = otto_emdio_bus_to_priv(phydev->mdio.bus);
>  	int port = otto_emdio_phy_to_port(phydev->mdio.bus, phydev->mdio.addr);
> +	struct otto_emdio_chan *chan = phydev->mdio.bus->priv;
>  	struct mii_bus *bus = phydev->mdio.bus;
>  	int ret;
>  
>  	if (port < 0)
>  		return;
>  
> +	/* avoid wrong cached page for next attachment */
> +	if (!priv->smi_bus_is_c45[chan->mdio_bus])
> +		priv->page[port] = 0;

[Severity: Medium]
Does this write to priv->page[port] need to be protected by priv->lock?

Looking at otto_emdio_read_c22() and otto_emdio_write_c22() introduced
earlier in this patch, accesses to priv->page[port] are protected by taking
priv->lock. Here in otto_emdio_notify_phy_detach(), the assignment happens
without acquiring priv->lock.

Could this cause a data race if a concurrent MDIO read/write ioctl occurs
while the PHY is being detached?

> +
>  	ret = otto_emdio_set_port_polling(priv, port, false);
>  	if (ret)
>  		dev_err(bus->parent, "failed to disable polling for port %d\n", port);

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260729160227.155613-1-markus.stockhausen@gmx.de?part=6