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

2019-07-25 Thread 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 
---
  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(, 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

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

2019-07-25 Thread Takashi Iwai 
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 
> ---
>  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(, 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