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Date:   Mon, 28 Oct 2019 15:40:24 +0100
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Takashi Iwai <tiwai@suse.de>
Cc:     syzbot <syzbot+8f2612936028bfd28f28@syzkaller.appspotmail.com>,
        allison@lohutok.net, alsa-devel@alsa-project.org,
        benquike@gmail.com, dan.carpenter@oracle.com, glider@google.com,
        linux-kernel@vger.kernel.org, perex@perex.cz,
        syzkaller-bugs@googlegroups.com, tglx@linutronix.de,
        tiwai@suse.com, wang6495@umn.edu, yuehaibing@huawei.com
Subject: Re: KMSAN: uninit-value in get_term_name
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On Mon, Oct 28, 2019 at 02:55:52PM +0100, Takashi Iwai wrote:
> On Mon, 28 Oct 2019 14:30:50 +0100,
> Greg KH wrote:
> > 
> > On Mon, Oct 28, 2019 at 02:13:20PM +0100, Takashi Iwai wrote:
> > > On Mon, 28 Oct 2019 11:32:07 +0100,
> > > syzbot wrote:
> > > > 
> > > > Uninit was stored to memory at:
> > > >  kmsan_save_stack_with_flags mm/kmsan/kmsan.c:151 [inline]
> > > >  kmsan_internal_chain_origin+0xbd/0x180 mm/kmsan/kmsan.c:319
> > > >  __msan_chain_origin+0x6b/0xd0 mm/kmsan/kmsan_instr.c:179
> > > >  parse_term_proc_unit+0x73d/0x7e0 sound/usb/mixer.c:896
> > > >  __check_input_term+0x13ef/0x2360 sound/usb/mixer.c:989
> > > 
> > > So this comes from the invalid descriptor for a processing unit, and
> > > it's very likely the same issue as already spotted -- the validator up
> > > to 5.3-rc4 had a bug that passed the invalid descriptor falsely.
> > > This should have been covered by 5.3-rc5, commit ba8bf0967a15 ("ALSA:
> > > usb-audio: Fix copy&paste error in the validator").
> > 
> > SHould we be backporting the validator to any older kernels as well?
> 
> Yes, that would be nice.  I didn't mark them for stable just because
> they are a bit largish and wanted to let them tested for 5.4 for a
> while.
> 
> The following commits are relevant (from top/old to bottom/new).
> 
> 57f8770620e9b51c61089751f0b5ad3dbe376ff2
>     ALSA: usb-audio: More validations of descriptor units
> 68e9fde245591d18200f8a9054cac22339437adb
>     ALSA: usb-audio: Simplify parse_audio_unit()
> 52c3e317a857091fd746e15179a637f32be4d337
>     ALSA: usb-audio: Unify the release of usb_mixer_elem_info objects
> b8e4f1fdfa422398c2d6c47bfb7d1feb3046d70a
>     ALSA: usb-audio: Remove superfluous bLength checks
> e0ccdef92653f8867e2d1667facfd3c23699f540
>     ALSA: usb-audio: Clean up check_input_term()
> 60849562a5db4a1eee2160167e4dce4590d3eafe
>     ALSA: usb-audio: Fix possible NULL dereference at create_yamaha_midi_quirk()
> b39e077fcb283dd96dd251a3abeba585402c61fe
>     ALSA: usb-audio: remove some dead code
> ba8bf0967a154796be15c4983603aad0b05c3138
>     ALSA: usb-audio: Fix copy&paste error in the validator
> 

Thanks, I'll look at these for the next round of kernels.

greg k-h