linux-kernel - Re: snd_seq_timer_open() NULL pointer dereference

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Message-ID: <s5hehfml3m8.wl%tiwai@suse.de>
Date:	Mon, 11 Mar 2013 09:53:03 +0100
From:	Takashi Iwai <tiwai@...e.de>
To:	Tommi Rantala <tt.rantala@...il.com>
Cc:	Jaroslav Kysela <perex@...ex.cz>, alsa-devel@...a-project.org,
	LKML <linux-kernel@...r.kernel.org>,
	Dave Jones <davej@...hat.com>
Subject: Re: snd_seq_timer_open() NULL pointer dereference

At Fri, 8 Mar 2013 20:59:11 +0200,
Tommi Rantala wrote:
> 
> 2013/3/8 Takashi Iwai <tiwai@...e.de>:
> > At Thu, 7 Mar 2013 21:59:32 +0200,
> > Tommi Rantala wrote:
> >>
> >> Hello,
> >>
> >> I'm hitting this while fuzzing the kernel with Trinity:
> >
> > The patch below fixes a clear bug in the code path.
> > Could you check whether it'll fit?
> >
> >
> > thanks,
> >
> > Takashi
> >
> > ---
> > From: Takashi Iwai <tiwai@...e.de>
> > Subject: [PATCH] ALSA: seq: Fix missing error handling in snd_seq_timer_open()
> >
> > snd_seq_timer_open() didn't catch the whole error path but let through
> > if the timer id is a slave.  This may lead to Oops by accessing the
> > uninitialized pointer.
> >
> > Signed-off-by: Takashi Iwai <tiwai@...e.de>
> 
> Confirmed, this fixes the bug. Thanks!
> 
> Reported-and-tested-by: Tommi Rantala <tt.rantala@...il.com>

Thanks for a quick check!  I merged the patch now.


Takashi


> > ---
> >  sound/core/seq/seq_timer.c | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/sound/core/seq/seq_timer.c b/sound/core/seq/seq_timer.c
> > index 160b1bd..24d44b2 100644
> > --- a/sound/core/seq/seq_timer.c
> > +++ b/sound/core/seq/seq_timer.c
> > @@ -290,10 +290,10 @@ int snd_seq_timer_open(struct snd_seq_queue *q)
> >                         tid.device = SNDRV_TIMER_GLOBAL_SYSTEM;
> >                         err = snd_timer_open(&t, str, &tid, q->queue);
> >                 }
> > -               if (err < 0) {
> > -                       snd_printk(KERN_ERR "seq fatal error: cannot create timer (%i)\n", err);
> > -                       return err;
> > -               }
> > +       }
> > +       if (err < 0) {
> > +               snd_printk(KERN_ERR "seq fatal error: cannot create timer (%i)\n", err);
> > +               return err;
> >         }
> >         t->callback = snd_seq_timer_interrupt;
> >         t->callback_data = q;
> > --
> > 1.8.1.4
> >
> 
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