linux-kernel - Re: [PATCH] can: mpc5xxx_can: check of

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Message-ID: <a4540f12-bedb-c81c-d998-9a2634a026db@pengutronix.de>
Date:   Mon, 23 Jul 2018 14:27:53 +0200
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Nicholas Mc Guire <der.herr@...r.at>
Cc:     Fabio Estevam <festevam@...il.com>,
        Nicholas Mc Guire <hofrat@...dl.org>,
        Wolfram Sang <w.sang@...gutronix.de>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        "David S. Miller" <davem@...emloft.net>, linux-can@...r.kernel.org,
        netdev <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] can: mpc5xxx_can: check of_iomap return before use

On 07/23/2018 01:57 PM, Nicholas Mc Guire wrote:
> On Mon, Jul 23, 2018 at 01:37:05PM +0200, Marc Kleine-Budde wrote:
>> On 07/09/2018 09:28 PM, Fabio Estevam wrote:
>>> On Mon, Jul 9, 2018 at 4:16 PM, Nicholas Mc Guire <hofrat@...dl.org> wrote:
>>>>  of_iompa() can return NULL so that return needs to be checked and NULL
>>>
>>> s/of_iompa/of_iomap/
>>>
>>>> treated as failure. While at it also take care of the missing
>>>> of_node_put() in the error path.
>>>>
>>>> Signed-off-by: Nicholas Mc Guire <hofrat@...dl.org>
>>>> Fixes: commit afa17a500a36 ("net/can: add driver for mscan family & mpc52xx_mscan")
>>>> ---
>>>>
>>>> Problem was found by an experimental coccinelle script
>>>>
>>>> Patch was compiletested with: mpc5200_defconfig + CONFIG_CAN=y,
>>>> CONFIG_CAN_MSCAN=y, CONFIG_CAN_MPC5XXX=y
>>>> (with a number of sparse warnings not related to the proposed change)
>>>>
>>>> Patch is against 4.18-rc3 (localversion-next is next-20180706)
>>>>
>>>>  drivers/net/can/mscan/mpc5xxx_can.c | 5 +++++
>>>>  1 file changed, 5 insertions(+)
>>>>
>>>> diff --git a/drivers/net/can/mscan/mpc5xxx_can.c b/drivers/net/can/mscan/mpc5xxx_can.c
>>>> index c7427bd..2949a38 100644
>>>> --- a/drivers/net/can/mscan/mpc5xxx_can.c
>>>> +++ b/drivers/net/can/mscan/mpc5xxx_can.c
>>>> @@ -86,6 +86,11 @@ static u32 mpc52xx_can_get_clock(struct platform_device *ofdev,
>>>>                 return 0;
>>>>         }
>>>>         cdm = of_iomap(np_cdm, 0);
>>>> +       if (!cdm) {
>>>> +               of_node_put(np_cdm);
>>>> +               dev_err(&ofdev->dev, "can't map clock node!\n");
>>>> +               return 0;
>>>
>>> I think you should return an error code here. -ENOMEM maybe?
>>
>> Can you send an updated version?
>>
> The way I understand the code the return value will be used
> as a frequency - the only valid error valeu thus is 0 here,
> so I think the return 0 is correct.

Yes. Looking at the code this makes sense.

Marc

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