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From: Dmitry Vyukov <dvyukov@google.com>
Date: Wed, 3 Feb 2016 14:25:23 +0100
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Subject: Re: sound: out-of-bounds write in snd_rawmidi_kernel_write1
To: Takashi Iwai <tiwai@suse.de>
Cc: alsa-devel@alsa-project.org, Jaroslav Kysela <perex@perex.cz>,
        LKML <linux-kernel@vger.kernel.org>,
        Alexander Potapenko <glider@google.com>,
        Kostya Serebryany <kcc@google.com>,
        syzkaller <syzkaller@googlegroups.com>,
        Sasha Levin <sasha.levin@oracle.com>
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On Wed, Feb 3, 2016 at 10:35 AM, Takashi Iwai <tiwai@suse.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.