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

[Vegard Nossum]

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