On Wed, 24 Jul 2019 14:13:27 +0200, Jia-Ju Bai wrote:

In snd_timer_proc_read(), there is an if statement on line 1204 to check whether timer->card is NULL: if (timer->card && timer->card->shutdown)

When timer->card is NULL, it is used on lines 1212 and 1215: timer->card->number

Thus, possible null-pointer dereferences may occur.

To fix these bugs, timer->card is checked before being used.

Both cases can (should) never happen. The SNDRV_TIMER_CLASS_CARD is always associated with a timer with a card object. Ditto for SNDRV_TIMER_CLASS_PCM, where a PCM is always tied with a card.

So, if any, this should be a WARN_ON(). But I doubt it being any useful.

thanks,

Takashi

These bugs are found by a static analysis tool STCheck written by us.

Signed-off-by: Jia-Ju Bai baijiaju1990@gmail.com

sound/core/timer.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/sound/core/timer.c b/sound/core/timer.c index 5c9fbf3f4340..967d06a3cdec 100644 --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -1208,11 +1208,13 @@ static void snd_timer_proc_read(struct snd_info_entry *entry, snd_iprintf(buffer, "G%i: ", timer->tmr_device); break; case SNDRV_TIMER_CLASS_CARD:

• 	snd_iprintf(buffer, "C%i-%i: ",
  

• 		    timer->card->number, timer->tmr_device);
  

• 	snd_iprintf(buffer, "C%i-%i: ", 
  

• 			timer->card ? timer->card->number : -1, 
  

• 			timer->tmr_device);
  break;
  

  case SNDRV_TIMER_CLASS_PCM:

• 	snd_iprintf(buffer, "P%i-%i-%i: ", timer->card->number,
  

• 	snd_iprintf(buffer, "P%i-%i-%i: ",
  

• 			timer->card ? timer->card->number : -1,
  	    timer->tmr_device, timer->tmr_subdevice);
  break;
  

  default:

-- 2.17.0