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

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Message-ID: <57E5746D.6020606@canonical.com>
Date:   Fri, 23 Sep 2016 19:29:01 +0100
From:   Colin Ian King <colin.king@...onical.com>
To:     Vaibhav Agarwal <vaibhav.sr@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     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 23/09/16 19:20, Vaibhav Agarwal wrote:
> 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.

Vaibhav, I'm currently traveling, so won't be able to check this until
next week, so if you would rather send a correct fix sooner rather me
re-sending a fix then I'm fine with that.

Thanks, Colin
> 
> --
> thanks,
> vaibhav
>>