Re: [alsa-devel] [PATCH 1/3] ALSA: timer: fix NULL pointer dereference in read()/ioctl() race

29 Aug 2016


      On 08/29/2016 09:02 AM, Takashi Iwai wrote:
...
On Mon, 29 Aug 2016 00:33:49 +0200,
Vegard Nossum wrote:
...
@@ -1602,15 +1602,25 @@ static int snd_timer_user_tselect(struct file *file,
   kfree(tu->tqueue);
   tu->tqueue = NULL;
   if (tu->tread) {

tu->tqueue = kmalloc(tu->queue_size * sizeof(struct snd_timer_tread),




struct snd_timer_tread *ttr;


ttr = kmalloc(tu->queue_size * sizeof(struct snd_timer_tread),
	     GFP_KERNEL);




if (tu->tqueue == NULL)




if (ttr) {


	kfree(tu->tqueue);


	tu->tqueue = ttr;



This looks like the double-tree, as you didn't remove the kfree() call
in the above.  But, I guess this change is superfluous when you
introduce the mutex at...
You're right, this hunk is garbage.
Please see the new patch (attached), I also changed the patch
description slightly to match the changes.
I'll start running some tests on the new patch.
Thanks!
Vegard

    