linux-kernel - Re: [PATCH] net: dsa: fix fixed-link-phy device leaks

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Date:   Wed, 16 Nov 2016 09:06:26 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Johan Hovold <johan@...nel.org>, Andrew Lunn <andrew@...n.ch>
Cc:     Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: dsa: fix fixed-link-phy device leaks

On 11/16/2016 06:47 AM, Johan Hovold wrote:
> Make sure to drop the reference taken by of_phy_find_device() when
> registering and deregistering the fixed-link PHY-device.
> 
> Note that we need to put both references held at deregistration.
> 
> Fixes: 39b0c705195e ("net: dsa: Allow configuration of CPU & DSA port
> speeds/duplex")
> Signed-off-by: Johan Hovold <johan@...nel.org>
> ---
> 
> Hi,
> 
> This is one has been compile tested only, but fixes a couple of leaks
> similar to one that was found in the cpsw driver for which I just posted
> a patch.
> 
> It turns out all drivers but DSA fail to deregister the fixed-link PHYs
> registered by of_phy_register_fixed_link(). Due to the way this
> interface was designed, deregistering such a PHY is a bit cumbersome and
> looks like it would benefit from a common helper.
> 
> However, perhaps the interface should instead be changed so that the PHY
> device is returned so that drivers do not need to use
> of_phy_find_device() when they need to access properties of the fixed
> link (e.g. as in dsu_cpu_dsa_setup below).
> 
> Thoughts?
> 
> Thanks,
> Johan
> 
> 
>  net/dsa/dsa.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c
> index a6902c1e2f28..798a6a776a5f 100644
> --- a/net/dsa/dsa.c
> +++ b/net/dsa/dsa.c
> @@ -233,6 +233,8 @@ int dsa_cpu_dsa_setup(struct dsa_switch *ds, struct device *dev,
>  		genphy_read_status(phydev);
>  		if (ds->ops->adjust_link)
>  			ds->ops->adjust_link(ds, port, phydev);
> +
> +		phy_device_free(phydev);	/* of_phy_find_device */
>  	}
>  
>  	return 0;
> @@ -509,8 +511,12 @@ void dsa_cpu_dsa_destroy(struct device_node *port_dn)
>  	if (of_phy_is_fixed_link(port_dn)) {
>  		phydev = of_phy_find_device(port_dn);
>  		if (phydev) {
> -			phy_device_free(phydev);
>  			fixed_phy_unregister(phydev);
> +			/* Put references taken by of_phy_find_device() and
> +			 * of_phy_register_fixed_link().
> +			 */
> +			phy_device_free(phydev);
> +			phy_device_free(phydev);

Double free, this looks bogus here. Actually would not this mean a
triple free since you already free in dsa_cpu_dsa_setup() which is
paired with dsa_cpu_dsa_destroy()?
-- 
Florian