netdev - RE: [PATCH net v2 1/3] net: phy: Fix PHY module checks

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Date:   Wed, 8 Feb 2017 07:57:58 +0000
From:   maowenan <maowenan@...wei.com>
To:     Florian Fainelli <f.fainelli@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "andrew@...n.ch" <andrew@...n.ch>,
        "rmk+kernel@...linux.org.uk" <rmk+kernel@...linux.org.uk>
Subject: RE: [PATCH net v2 1/3] net: phy: Fix PHY module checks



> -----Original Message-----
> From: Florian Fainelli [mailto:f.fainelli@...il.com]
> Sent: Wednesday, February 08, 2017 3:38 PM
> To: netdev@...r.kernel.org
> Cc: davem@...emloft.net; andrew@...n.ch; rmk+kernel@...linux.org.uk;
> maowenan; Florian Fainelli
> Subject: [PATCH net v2 1/3] net: phy: Fix PHY module checks
> 
> 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
> derference d->driver. Update phy_attach_direct() and phy_detach() accordingly
> to be resilient to these cases.
> 
> Even though the Generic PHY driver defaults to phy_probe() which can hardly
> fail at the moment, let's fix the label so we don't call phy_detach() on a network
> device we have not attached yet.
> 
> 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 | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c index
> 0d8f4d3847f6..bde240bf8d7b 100644
> --- a/drivers/net/phy/phy_device.c
> +++ b/drivers/net/phy/phy_device.c
> @@ -920,7 +920,7 @@ int phy_attach_direct(struct net_device *dev, struct
> phy_device *phydev,
>  		return -EIO;
>  	}
> 
> -	if (!try_module_get(d->driver->owner)) {
> +	if (d->driver && !try_module_get(d->driver->owner)) {
>  		dev_err(&dev->dev, "failed to get the device driver module\n");
>  		return -EIO;

Hi Florian,
  Here "return -EIO" will miss decreasing bus->owner reference count.

Mao Wenan

>  	}
> @@ -943,7 +943,7 @@ int phy_attach_direct(struct net_device *dev, struct
> phy_device *phydev,
>  			err = device_bind_driver(d);
> 
>  		if (err)
> -			goto error;
> +			goto error_put_device;
>  	}
> 
>  	if (phydev->attached_dev) {
> @@ -981,6 +981,7 @@ int phy_attach_direct(struct net_device *dev, struct
> phy_device *phydev,
> 
>  error:
>  	phy_detach(phydev);
> +error_put_device:
>  	put_device(d);
>  	module_put(d->driver->owner);
>  	if (ndev_owner != bus->owner)
> @@ -1065,7 +1066,8 @@ void phy_detach(struct phy_device *phydev)
>  	bus = phydev->mdio.bus;
> 
>  	put_device(&phydev->mdio.dev);
> -	module_put(phydev->mdio.dev.driver->owner);
> +	if (phydev->mdio.dev.driver)
> +		module_put(phydev->mdio.dev.driver->owner);
>  	if (ndev_owner != bus->owner)
>  		module_put(bus->owner);
>  }
> --
> 2.9.3