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

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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
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