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

2 Sep 2016


      On 08/29/2016 09:14 AM, Vegard Nossum wrote:
...
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.
I tested the new patch (from the email I'm replying to). It seems to
work for me.
Thanks,
Vegard

    