Re: [PATCH] ALSA: i2c: ak4xxx-adda: Fix a possible null pointer dereference in build_adc_controls()

[Jia-Ju Bai]

On 2019/7/25 23:52, Takashi Iwai wrote:
> On Thu, 25 Jul 2019 10:27:33 +0200,
> Jia-Ju Bai wrote:
> > In build_adc_controls(), there is an if statement on line 773 to check
> > whether ak->adc_info is NULL:
> > 	if (! ak->adc_info ||
> > 		! ak->adc_info[mixer_ch].switch_name)
> >
> > When ak->adc_info is NULL, it is used on line 792:
> >      knew.name = ak->adc_info[mixer_ch].selector_name;
> >
> > Thus, a possible null-pointer dereference may occur.
> >
> > To fix this bug, referring to lines 773 and 774, ak->adc_info
> > and ak->adc_info[mixer_ch].selector_name are checked before being used.
> >
> > This bug is found by a static analysis tool STCheck written by us.
> >
> > Signed-off-by: Jia-Ju Bai <baijiaju1990@xxxxxxxxx>
> > ---
> >   sound/i2c/other/ak4xxx-adda.c | 6 ++++--
> >   1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/sound/i2c/other/ak4xxx-adda.c b/sound/i2c/other/ak4xxx-adda.c
> > index 5f59316f982a..9a891470e84a 100644
> > --- a/sound/i2c/other/ak4xxx-adda.c
> > +++ b/sound/i2c/other/ak4xxx-adda.c
> > @@ -775,11 +775,13 @@ static int build_adc_controls(struct snd_akm4xxx *ak)
> >   				return err;
> >   
> >   			memset(&knew, 0, sizeof(knew));
> > -			knew.name = ak->adc_info[mixer_ch].selector_name;
> > -			if (!knew.name) {
> > +			if (! ak->adc_info ||
> > +				! ak->adc_info[mixer_ch].selector_name) {
> >   				knew.name = "Capture Channel";
> >   				knew.index = mixer_ch + ak->idx_offset * 2;
> >   			}
> > +			else
> > +				knew.name = ak->adc_info[mixer_ch].selector_name;
> >   
> >   			knew.iface = SNDRV_CTL_ELEM_IFACE_MIXER;
> >   			knew.info = ak4xxx_capture_source_info;
> The code change itself looks good, but please follow the standard
> coding style.  In short: please run checkpatch.pl, fix errors (some
> warnings may be ignored) and resubmit.

Okay, thanks for the advice.
I will send a v2 patch.


Best wishes,
Jia-Ju Bai