netdev - Re: [PATCH] net: renesas: fix a potential NULL pointer dereference

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Date:   Mon, 11 Mar 2019 13:43:18 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Kangjie Lu <kjlu@....edu>
Cc:     pakki001@....edu, "David S. Miller" <davem@...emloft.net>,
        Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Vladimir Barinov <vladimir.barinov@...entembedded.com>,
        Chris Brandt <chris.brandt@...esas.com>,
        netdev <netdev@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] net: renesas: fix a potential NULL pointer dereference

Hello!

On 03/11/2019 10:43 AM, Geert Uytterhoeven wrote:

>> In case of_get_phy_mode fails, the fix returns NULL to avoid
>> the NULL pointer dereference.
>>
>> Signed-off-by: Kangjie Lu <kjlu@....edu>
> 
> Thanks for your patch!
> 
>> --- a/drivers/net/ethernet/renesas/sh_eth.c
>> +++ b/drivers/net/ethernet/renesas/sh_eth.c
>> @@ -3187,6 +3187,8 @@ static struct sh_eth_plat_data *sh_eth_parse_dt(struct device *dev)
>>                 return NULL;
>>
>>         pdata->phy_interface = of_get_phy_mode(np);
>> +       if (unlikely(!pdata->phy_interface))
>> +               return NULL;
> 
> of_get_phy_mode() does not return a pointer, but a phy mode index.
> Hence zero is a valid value.
> 
> So I'm wondering where is the potential NULL pointer dereference?

   Hm, not seeing NULL deref as well...

> Perhaps we do need to check for negative error codes?
> Or is this already handled later, by {of_,}phy_connect()?

   Not seeing such handling too...
   The v2 patch seems good though, as the "phy-mode" prop is mandatory anyway.

> Gr{oetje,eeting}s,
> 
>                         Geert

MBR, Sergei