linux-kernel - Re: sound: out-of-bounds write in snd_rawmidi_kernel

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Date:	Wed, 3 Feb 2016 14:25:23 +0100
From:	Dmitry Vyukov <dvyukov@...gle.com>
To:	Takashi Iwai <tiwai@...e.de>
Cc:	alsa-devel@...a-project.org, Jaroslav Kysela <perex@...ex.cz>,
	LKML <linux-kernel@...r.kernel.org>,
	Alexander Potapenko <glider@...gle.com>,
	Kostya Serebryany <kcc@...gle.com>,
	syzkaller <syzkaller@...glegroups.com>,
	Sasha Levin <sasha.levin@...cle.com>
Subject: Re: sound: out-of-bounds write in snd_rawmidi_kernel_write1

On Wed, Feb 3, 2016 at 10:35 AM, Takashi Iwai <tiwai@...e.de> 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?

Yes, it was MTPAV. There is only generic code in the stack traces, so
I though it may be a generic issue. Though, of course, the driver
could mess things already.
I've dropped CONFIG_SND_MTPAV now.