[PATCH] ASoC: Intel: Skylake: Check the kcontrol against NULL

[Guenter Roeck]

On Thu, Dec 10, 2020 at 7:55 AM Gorski, Mateusz <
mateusz.gorski at linux.intel.com> wrote:

>
> > There is no check for the kcontrol against NULL and in some cases
> > it causes kernel to crash.
> >
> > Fixes: 2d744ecf2b984 ("ASoC: Intel: Skylake: Automatic DMIC format
> configuration according to information from NHLT")
> > Cc: <stable at vger.kernel.org> # 5.4+
> > Signed-off-by: Lukasz Majczak <lma at semihalf.com>
> > ---
> >   sound/soc/intel/skylake/skl-topology.c | 14 ++++++++++----
> >   1 file changed, 10 insertions(+), 4 deletions(-)
> >
> > diff --git a/sound/soc/intel/skylake/skl-topology.c
> b/sound/soc/intel/skylake/skl-topology.c
> > index ae466cd592922..c9abbe4ff0ba3 100644
> > --- a/sound/soc/intel/skylake/skl-topology.c
> > +++ b/sound/soc/intel/skylake/skl-topology.c
> > @@ -3618,12 +3618,18 @@ static void skl_tplg_complete(struct
> snd_soc_component *component)
> >       int i;
> >
> >       list_for_each_entry(dobj, &component->dobj_list, list) {
> > -             struct snd_kcontrol *kcontrol = dobj->control.kcontrol;
> > -             struct soc_enum *se =
> > -                     (struct soc_enum *)kcontrol->private_value;
> > -             char **texts = dobj->control.dtexts;
> > +             struct snd_kcontrol *kcontrol;
> > +             struct soc_enum *se;
> > +             char **texts;
> >               char chan_text[4];
> >
> > +             kcontrol = dobj->control.kcontrol;
> > +             if(!kcontrol)
> > +                     continue;
> > +
> > +             se = (struct soc_enum *)kcontrol->private_value;
> > +             texts = dobj->control.dtexts;
> > +
> >               if (dobj->type != SND_SOC_DOBJ_ENUM ||
> >                   dobj->control.kcontrol->put !=
> >                   skl_tplg_multi_config_set_dmic)
> >
> > base-commit: 69fe63aa100220c8fd1f451dd54dd0895df1441d
>
>
> Thanks for pointing out and fixing this. This check was obviously
> missing there. I did a quick verification on few of our platforms,
> encountered no issues, so:
>
>      Reviewed-by: Mateusz Gorski <mateusz.gorski at linux.intel.com>
>
>
> Also, could you please:
>
> - describe the affected configuration (used machine driver or audio card
> name, device name),
>

Primarily Google Pixelbook. However, this can happen whenever
dobj->type != SND_SOC_DOBJ_ENUM. For many of those other types,
kcontrol is not set. It is pure luck that the problem is not seen
everywhere,
and it seems to be compiler dependent. [Some compilers or compiler
versions only assign se when needed, ie after the if() statement].

Guenter


> - share full dmesg logs from one of said crashes,
> - copy the output of "amixer -c0 controls" command executed on affected
> device.
>
> These would be useful information for us to further improve our
> validation and help us with debugging.
>
>
> Thanks,
>
> Mateusz
>
>
>