Re: sound: out-of-bounds write in snd_rawmidi_kernel_write1

From	Takashi Iwai <tiwai@suse.de>
Newsgroups	linux.kernel
Subject	Re: sound: out-of-bounds write in snd_rawmidi_kernel_write1
Date	2016-02-03 12:40 +0100
Message-ID	<qY3WW-1lI-19@gated-at.bofh.it> (permalink)
References	<qY1s6-83z-25@gated-at.bofh.it> <qY24O-aO-5@gated-at.bofh.it> <qY2ev-ew-21@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Wed, 03 Feb 2016 10:41:14 +0100,
Takashi Iwai wrote:
> 
> On Wed, 03 Feb 2016 10:35:14 +0100,
> Takashi Iwai wrote:
> > 
> > On Wed, 03 Feb 2016 09:57:50 +0100,
> > Dmitry Vyukov wrote:
> > > 
> > > Hello,
> > > 
> > > The following program triggers an out-of-bounds write in
> > > snd_rawmidi_kernel_write1 (run in parallel loop). It seems to try to
> > > copy -1 bytes (aka 4GB) from user space into kernel smashing all on
> > > its way.
> > 
> > What card is /dev/midi3?  Please check /proc/asound/cards.
> > Is it MTPAV?
> 
> In anyway the patch below should paper over it.  But it's still
> strange that it gets a negative value there.  Could you put
> 
>    WARN_ON(count1 < 0)
> 
> before the newly added check?
> 
> I tried it locally with virmidi but it didn't appear, so far.  Maybe
> my setup is too slow and has fewer CPUs than yours.

Scratch my previous patch, I could reproduce the issue on a faster
machine in my office now :)  Will work on it.


Takashi

Thread

sound: out-of-bounds write in snd_rawmidi_kernel_write1 Dmitry Vyukov <dvyukov@google.com> - 2016-02-03 10:00 +0100
  Re: sound: out-of-bounds write in snd_rawmidi_kernel_write1 Takashi Iwai <tiwai@suse.de> - 2016-02-03 10:40 +0100
    Re: sound: out-of-bounds write in snd_rawmidi_kernel_write1 Takashi Iwai <tiwai@suse.de> - 2016-02-03 10:50 +0100
      Re: sound: out-of-bounds write in snd_rawmidi_kernel_write1 Takashi Iwai <tiwai@suse.de> - 2016-02-03 12:40 +0100
        Re: sound: out-of-bounds write in snd_rawmidi_kernel_write1 Takashi Iwai <tiwai@suse.de> - 2016-02-03 13:10 +0100
          Re: sound: out-of-bounds write in snd_rawmidi_kernel_write1 Dmitry Vyukov <dvyukov@google.com> - 2016-02-03 14:40 +0100
            Re: sound: out-of-bounds write in snd_rawmidi_kernel_write1 Takashi Iwai <tiwai@suse.de> - 2016-02-03 15:30 +0100
    Re: sound: out-of-bounds write in snd_rawmidi_kernel_write1 Dmitry Vyukov <dvyukov@google.com> - 2016-02-03 14:30 +0100

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