netdev - Re: [PATCH v3] net: phy: fix uninitalized WOL parameters in phy_ethtool_get

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Date:	Thu, 13 Mar 2014 10:14:21 +0000
From:	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
To:	Ben Hutchings <ben@...adent.org.uk>
CC:	David Miller <davem@...emloft.net>,
	Florian Fainelli <f.fainelli@...il.com>,
	netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] net: phy: fix uninitalized WOL parameters in phy_ethtool_get_wol

On 03/13/2014 02:21 AM, Ben Hutchings wrote:
> On Wed, 2014-03-12 at 00:02 +0100, Sebastian Hesselbarth wrote:
>> phy_ethtool_get_wol is a helper to get current WOL settings from
>> a phy device. When using this helper on a PHY without .get_wol
>> callback, struct ethtool_wolinfo is never set-up correctly and
>> may contain misleading information about WOL status.
>>
>> To fix this, always zero relevant fields of struct ethtool_wolinfo
>> regardless of .get_wol callback availability.
>
> Sorry, I still disagree with this.

Which is really fine with me. Thanks for constantly commenting this.

> You're trying to make phy_ethtool_get_wol() do two subtly different
> things:
> - Provide an implementation of ethtool_ops::get_wol, leaving the net
>    driver only to look up phy_device
> - Provide a standalone function for executing ETHTOOL_GWOL on a
>    phy_device
>
> You may notice that phy_suspend() already sets wol.cmd = ETHTOOL_GWOL.

Yeah, which was added by me because I misinterpreted phy_ethtool_get_wol
depending on it. It doesn't because we just "reuse" struct
ethtool_wolinfo.

> So it seems to me like it's taking responsibility for initialising the
> structure like ethtool_get_wol() does.  The bug is then that
> phy_suspend() doesn't clear the rest of the structure.  That is not the
> responsibility of phy_ethtool_get_wol().

I agree that public ethtool_get_wol should clear the struct, but I am
not so happy to have an in-kernel API depend on the caller to setup the
struct. In any way, if there are strong reasons not to clear struct
ethtool_wolinfo again in phy_ethtool_get_wol, I can properly clear it
in phy_suspend instead. I don't have a strong opinion about it.

Sebastian

>> Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
>> Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
>> ---
>> Changelog:
>> v1->v2:
>> - clear whole struct ethtool_wolinfo
>> - check for non-NULL phy_device
>> v2->v3:
>> - only clear ->supported and ->wolopts (Suggested by Ben Hutchings)
>>
>> Cc: David Miller <davem@...emloft.net>
>> Cc: Florian Fainelli <f.fainelli@...il.com>
>> Cc: Ben Hutchings <ben@...adent.org.uk>
>> Cc: netdev@...r.kernel.org
>> Cc: linux-arm-kernel@...ts.infradead.org
>> Cc: linux-kernel@...r.kernel.org
>> ---
>>   drivers/net/phy/phy.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
>> index 19c9eca0ef26..94234a91a50f 100644
>> --- a/drivers/net/phy/phy.c
>> +++ b/drivers/net/phy/phy.c
>> @@ -1092,7 +1092,9 @@ EXPORT_SYMBOL(phy_ethtool_set_wol);
>>
>>   void phy_ethtool_get_wol(struct phy_device *phydev, struct ethtool_wolinfo *wol)
>>   {
>> -	if (phydev->drv->get_wol)
>> +	wol->supported = wol->wolopts = 0;
>> +
>> +	if (phydev && phydev->drv->get_wol)
>>   		phydev->drv->get_wol(phydev, wol);
>>   }
>>   EXPORT_SYMBOL(phy_ethtool_get_wol);
>

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