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

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@gmail.com

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.

thanks,

Takashi