linux-kernel - Re: [PATCH v2] net: renesas: fix a missing check of of_get_phy

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Message-ID: <20b2afad-4983-3d97-2440-9745352342da@cogentembedded.com>
Date:   Mon, 11 Mar 2019 17:18:29 +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>,
        Simon Horman <horms+renesas@...ge.net.au>,
        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 v2] net: renesas: fix a missing check of of_get_phy_mode

On 03/11/2019 01:59 PM, Geert Uytterhoeven wrote:

>> of_get_phy_mode may fail and return a negative error code;
>> the fix checks the return value of of_get_phy_mode and
>> returns NULL of it fails.
>>
>> Signed-off-by: Kangjie Lu <kjlu@....edu>
> 
>> --- 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 (pdata->phy_interface < 0)
>> +               return NULL;
> 
> sh_eth_plat_data.phy_interface has type phy_interface_t.
> This is an enum containing only positive values, hence it is unsigned.
> So the condition can never be true.

   Good catch, thank you!
   My gcc doesn't warn but doesn't generate the code for the branch either...

[...]

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

MBR, Sergei