[bug report] ALSA: hda - Don't register a cb func if it is registered already

[Hui Wang]

On 10/22/20 1:27 AM, Dan Carpenter wrote:
> On Wed, Oct 21, 2020 at 11:03:11PM +0800, Hui Wang wrote:
>> Looks like this will not bring problem on patch_sigmatel.c, NULL and valid
>> kernel pointer are same for IS_ERR(), they will not make IS_ERR() come true.
>>
> Correct, but that is the problem.  You can dereference a valid pointer
> but you can't dereference a NULL.
>
>> On 10/21/20 10:21 PM, Hui Wang wrote:
>>> On 10/21/20 8:19 PM, Dan Carpenter wrote:
>>>> Hello Hui Wang,
>>>>
>>>> The patch f4794c6064a8: "ALSA: hda - Don't register a cb func if it
>>>> is registered already" from Sep 30, 2020, leads to the following
>>>> static checker warning:
>>>>
>>>>      sound/pci/hda/patch_sigmatel.c:3075 stac92hd71bxx_fixup_hp_m4()
>>>>      warn: 'jack' can also be NULL
>>>>
>>>> sound/pci/hda/patch_sigmatel.c
>>>>     3069          /* Enable VREF power saving on GPIO1 detect */
>>>>     3070          snd_hda_codec_write_cache(codec, codec->core.afg, 0,
>>>>     3071 AC_VERB_SET_GPIO_UNSOLICITED_RSP_MASK, 0x02);
>>>>     3072          jack = snd_hda_jack_detect_enable_callback(codec,
>>>> codec->core.afg,
>>>>     3073 stac_vref_event);
>>>>
>>>> Originally snd_hda_jack_detect_enable_callback() would not return NULL
>>>> here.
>>>>
>>>>     3074          if (!IS_ERR(jack))
>>>>     3075                  jack->private_data = 0x02;
> So if "jack" is NULL then it will say it's not an error pointer so it
> will try to assign jack->private_data = 0x02; and oops.

Right. Will fix it.

Thanks

>
> regards,
> dan carpenter
>