Re: [net-next,v21,2/7] net: mtip: The L2 switch driver for imx287

[Jakub Kicinski <kuba@kernel.org>]

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---
net: mtip: The L2 switch driver for imx287

This patch introduces support for the MTIP L2 switch embedded in the
imx287 SoC. It provides the core driver infrastructure including DMA
initialization, PHY/MDIO handling, and net device operations.

> diff --git a/drivers/net/ethernet/freescale/mtipsw/mtipl2sw.c b/drivers/net/ethernet/freescale/mtipsw/mtipl2sw.c
> new file mode 100644
> index 000000000000..7b61ba9642e3
> --- /dev/null
> +++ b/drivers/net/ethernet/freescale/mtipsw/mtipl2sw.c

[ ... ]

> +static int mtip_mii_probe(struct net_device *dev)
> +{
> +	struct mtip_ndev_priv *priv = netdev_priv(dev);
> +	struct switch_enet_private *fep = priv->fep;
> +	struct phy_device *phy_dev = NULL;
> +	int port_idx = priv->portnum - 1;
> +
> +	if (fep->phy_np[port_idx]) {
> +		phy_dev = of_phy_connect(dev, fep->phy_np[port_idx],
> +					 &mtip_adjust_link, 0,
> +					 fep->phy_interface[port_idx]);
> +		if (!phy_dev) {
> +			netdev_err(dev, "Unable to connect to phy\n");
> +			return -ENODEV;
> +		}
> +	}
> +
> +	phy_set_max_speed(phy_dev, 100);

If fep->phy_np[port_idx] is NULL (no phy-handle in device tree), the
if block is skipped entirely. In that case phy_dev remains NULL from
initialization, and phy_set_max_speed() is called with a NULL pointer.

phy_set_max_speed() dereferences phydev->supported via __set_phy_supported(),
which would cause a NULL pointer dereference crash when the interface
is opened.

Should phy_set_max_speed() and the subsequent accesses to
fep->phy_dev[port_idx] be moved inside the if block, or should the
function return an error when phy_np is NULL?

> +	fep->phy_dev[port_idx] = phy_dev;
> +	fep->link[port_idx] = 0;
> +	fep->full_duplex[port_idx] = 0;
> +
> +	dev_dbg(&dev->dev,
> +		"MTIP PHY driver [%s] (mii_bus:phy_addr=%s, irq=%d)\n",
> +		fep->phy_dev[port_idx]->drv->name,

This debug print also dereferences fep->phy_dev[port_idx]->drv->name,
which would crash if phy_dev is NULL.

> +		phydev_name(fep->phy_dev[port_idx]),
> +		fep->phy_dev[port_idx]->irq);
> +
> +	return 0;
> +}
-- 
pw-bot: cr