linux-kernel - Re: [PATCH] net: ethernet: mediatek: add NULL check on of_match

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Date:   Fri, 07 Jul 2017 15:08:31 -0500
From:   "Gustavo A. R. Silva" <garsilva@...eddedor.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Felix Fietkau <nbd@...nwrt.org>, John Crispin <blogic@...nwrt.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        netdev@...r.kernel.org, linux-mediatek@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] net: ethernet: mediatek: add NULL check on
 of_match_device() return value

Hi Andrew,

Quoting Andrew Lunn <andrew@...n.ch>:

> On Fri, Jul 07, 2017 at 02:11:35AM -0500, Gustavo A. R. Silva wrote:
>> Check return value from call to of_match_device()
>> in order to prevent a NULL pointer dereference.
>>
>> In case of NULL print error message and return -ENODEV
>>
>> Signed-off-by: Gustavo A. R. Silva <garsilva@...eddedor.com>
>> ---
>>  drivers/net/ethernet/mediatek/mtk_eth_soc.c | 5 +++++
>>  1 file changed, 5 insertions(+)
>>
>> diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c  
>> b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
>> index adaaafc..6a77dea 100644
>> --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
>> +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
>> @@ -2408,6 +2408,11 @@ static int mtk_probe(struct platform_device *pdev)
>>  	int i;
>>
>>  	match = of_match_device(of_mtk_match, &pdev->dev);
>> +	if (!match) {
>> +		dev_err(&pdev->dev, "failed to match device\n");
>> +		return -ENODEV;
>> +	}
>> +
>>  	soc = (struct mtk_soc_data *)match->data;
>
> Hi Gustavo
>
> I think you are fixing the wrong thing. The soc variable is unused. Also,
>
> const struct of_device_id of_mtk_match[] = {
>         { .compatible = "mediatek,mt2701-eth" },
>         {},
> };
>
> So match->data is NULL. This code is all pointless and should be
> removed, rather than try to avoid a NULL pointer dereference which can
> not actually happen.
>

You are right. Thank you for pointing it out. I'll remove that code  
and send a new patch shortly.

Thanks!
--
Gustavo A. R. Silva