netdev - Re: [PATCH net v3 1/3] net: phy: Fix PHY module checks and NULL deref in phy_attach

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Date:   Wed, 8 Feb 2017 16:15:34 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     netdev@...r.kernel.org
Cc:     maowenan <maowenan@...wei.com>, andrew@...n.ch,
        rmk+kernel@...linux.org.uk, festevam@...il.com,
        davem@...emloft.net, nikita.yoush@...entembedded.com
Subject: Re: [PATCH net v3 1/3] net: phy: Fix PHY module checks and NULL deref
 in phy_attach_direct()

On 02/08/2017 04:13 PM, Florian Fainelli wrote:
> The Generic PHY drivers gets assigned after we checked that the current
> PHY driver is NULL, so we need to check a few things before we can
> safely dereference d->driver. This would be causing a NULL deference to
> occur when a system binds to the Generic PHY driver. Update
> phy_attach_direct() to do the following:
> 
> - grab the driver module reference after we have assigned the Generic
>   PHY drivers accordingly
> 
> - update the error path to clean up the module reference in case the
>   Generic PHY probe function fails
> 
> Fixes: cafe8df8b9bc ("net: phy: Fix lack of reference count on PHY driver")
> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
> ---
>  drivers/net/phy/phy_device.c | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
> index 0d8f4d3847f6..d63d190a95ef 100644
> --- a/drivers/net/phy/phy_device.c
> +++ b/drivers/net/phy/phy_device.c
> @@ -908,6 +908,7 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev,
>  	struct module *ndev_owner = dev->dev.parent->driver->owner;
>  	struct mii_bus *bus = phydev->mdio.bus;
>  	struct device *d = &phydev->mdio.dev;
> +	bool using_genphy = false;
>  	int err;
>  
>  	/* For Ethernet device drivers that register their own MDIO bus, we
> @@ -938,12 +939,22 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev,
>  			d->driver =
>  				&genphy_driver[GENPHY_DRV_1G].mdiodrv.driver;
>  
> +		using_genphy = true;
> +	}
> +
> +	if (!try_module_get(d->driver->owner)) {
> +		dev_err(&dev->dev, "failed to get the device driver module\n");
> +		err = -EIO;
> +		goto error_put_device;
> +	}

And still not correct, since we need to remove the other hunk, one day I
will learn how to properly rebase my work... will submit a v4 shortly.
-- 
Florian