Re: [PATCH 2/2] ASoC: Add BUG() assertion if max98095_get_bq_channel returns -EINVAL

[Dave Young <hidave.darkstar@gmail.com>]

On Thu, Sep 29, 2011 at 9:52 AM, Ryan Mallon <rmallon@gmail.com> wrote:
> On 29/09/11 11:35, Dave Young wrote:
>
>> On Thu, Sep 29, 2011 at 7:19 AM, Ryan Mallon <rmallon@gmail.com> wrote:
>>> On 29/09/11 00:02, Axel Lin wrote:
>>>> The callers use the return value of max98095_get_bq_channel as array index to
>>>> access max98095->dai[] array.
>>>> Add BUG() assertion for out of bound access of max98095->dai[] array.
>>>
>>> Same here, fix the problem in the callers.
>>>
>>> ----
>>> Check the return value of max98095_get_bq_channel in the callers and
>>> propagate any errors up. Remove the BUG_ON(channel > 1) since
>>> max98095_get_bq_channel never returns a value larger than 1.
>>>
>>> Signed-off-by: Ryan Mallon <rmallon@gmail.com>
>>> ---
>>>
>>> diff --git a/sound/soc/codecs/max98095.c b/sound/soc/codecs/max98095.c
>>> index 668434d..55eccea 100644
>>> --- a/sound/soc/codecs/max98095.c
>>> +++ b/sound/soc/codecs/max98095.c
>>> @@ -2014,7 +2014,8 @@ static int max98095_put_bq_enum(struct snd_kcontrol *kcontrol,
>>>        int fs, best, best_val, i;
>>>        int regmask, regsave;
>>>
>>> -       BUG_ON(channel > 1);
>>> +       if (channel < 0)
>>> +               return channel;
>>
>> If use BUG() happens in  max98095_get_bq_channel, it will not return here?
>
>
> Not quite sure what you mean?

I means if Axel Lin's patch applied, and CONFIG_BUG is on, it will
panic firstly the if condition will be never entered.

>
> If CONFIG_BUG was not enabled for the original version, then it would
> not return at the BUG_ON and would either crash or cause odd behaviour
> if it tried to index channel as -1.
>
> My patch is removing the BUG_ON and replacing it with a proper check and
> return. It doesn't need to check > 1 since max98095_get_bq_channel never
> returns that.
>
> My understanding is that device drivers, in general, should not call
> BUG. BUG is for unrecoverable errors which leave the kernel in some
> unstable state. Here we can just return an error code.

Agree

>
> ~Ryan
>
>>
>>>
>>>        if (!pdata || !max98095->bq_textcnt)
>>>                return 0;
>>> @@ -2069,6 +2070,9 @@ static int max98095_get_bq_enum(struct snd_kcontrol *kcontrol,
>>>        int channel = max98095_get_bq_channel(kcontrol->id.name);
>>>        struct max98095_cdata *cdata;
>>>
>>> +       if (channel < 0)
>>> +               return channel;
>>> +
>>>        cdata = &max98095->dai[channel];
>>>        ucontrol->value.enumerated.item[0] = cdata->bq_sel;
>>>
>>>
>>> --
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>>
>>
>>
>
>
>



-- 
Regards
Dave