linux-kernel - Re: [PATCH] greybus: audio: ensure module is set to avoid crash on dev

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Message-ID: <CAAs364-6G0eqix6gc85ZEOM47tOp_BeQ60EgtA=FbekzOgURXw@mail.gmail.com>
Date:   Fri, 23 Sep 2016 23:50:58 +0530
From:   Vaibhav Agarwal <vaibhav.sr@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Colin King <colin.king@...onical.com>,
        Johan Hovold <johan@...nel.org>, Alex Elder <elder@...nel.org>,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] greybus: audio: ensure module is set to avoid crash on
 dev_err message

On Fri, Sep 23, 2016 at 10:28 PM, Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
> On Fri, Sep 23, 2016 at 11:25:40AM +0100, Colin King wrote:
>> From: Colin Ian King <colin.king@...onical.com>
>>
>> Currently, if info is null, the dev_err message is dereferencing an
>> uninitialized module pointer.  Instead, initialize module before the
>> dev_err call to fix this issue.
>>
>> Found using static analysis with cppcheck:
>> [drivers/staging/greybus/audio_topology.c:175]: (error)
>>   Uninitialized variable: module
>>
>> Signed-off-by: Colin Ian King <colin.king@...onical.com>
>> ---
>>  drivers/staging/greybus/audio_topology.c | 6 +++---
>>  1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/staging/greybus/audio_topology.c b/drivers/staging/greybus/audio_topology.c
>> index 5eef536..c43a959 100644
>> --- a/drivers/staging/greybus/audio_topology.c
>> +++ b/drivers/staging/greybus/audio_topology.c
>> @@ -171,6 +171,9 @@ static int gbcodec_mixer_ctl_info(struct snd_kcontrol *kcontrol,
>>       data = (struct gbaudio_ctl_pvt *)kcontrol->private_value;
>>       info = (struct gb_audio_ctl_elem_info *)data->info;
>>
>> +     module = find_gb_module(gbcodec, kcontrol->id.name);
>> +     if (!module)
>> +             return -EINVAL;
>
> How do you know you can get a module at this point in time, you haven't
> looked at the type of info to know that?
>
> I agree that there is an issue here, but I don't think this is the
> correct fix.  Vaibhav?

Actually, fetching module is not related to info->type. However it is
only required in case of ENUMERATED element_type, thus used in
specific case. Also, I think it's better to use codec->dev in the err
message and align with other err_msg in this function.

Hi Colin, thanks for sharing this patch. Do you mind updating this
patch including my above suggestion? Otherwise, I can share a separate
patch.

--
thanks,
vaibhav
>