linux-kernel - Re: [PATCH AUTOSEL 5.13 03/12] ASoC: wm_adsp: Let soc_cleanup_component

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Date:   Thu, 19 Aug 2021 09:26:34 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     Charles Keepax <ckeepax@...nsource.cirrus.com>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Lucas Tanure <tanureal@...nsource.cirrus.com>,
        Mark Brown <broonie@...nel.org>, patches@...nsource.cirrus.com,
        alsa-devel@...a-project.org
Subject: Re: [PATCH AUTOSEL 5.13 03/12] ASoC: wm_adsp: Let
 soc_cleanup_component_debugfs remove debugfs

On Wed, Aug 18, 2021 at 01:15:44PM +0000, Charles Keepax wrote:
>On Mon, Aug 16, 2021 at 08:35:27PM -0400, Sasha Levin wrote:
>> From: Lucas Tanure <tanureal@...nsource.cirrus.com>
>>
>> [ Upstream commit acbf58e530416e167c3b323111f4013d9f2b0a7d ]
>>
>> soc_cleanup_component_debugfs will debugfs_remove_recursive
>> the component->debugfs_root, so adsp doesn't need to also
>> remove the same entry.
>> By doing that adsp also creates a race with core component,
>> which causes a NULL pointer dereference
>>
>> Signed-off-by: Lucas Tanure <tanureal@...nsource.cirrus.com>
>> Link: https://lore.kernel.org/r/20210728104416.636591-1-tanureal@opensource.cirrus.com
>> Signed-off-by: Mark Brown <broonie@...nel.org>
>> Signed-off-by: Sasha Levin <sashal@...nel.org>
>> ---
>>  sound/soc/codecs/wm_adsp.c | 1 -
>>  1 file changed, 1 deletion(-)
>>
>> diff --git a/sound/soc/codecs/wm_adsp.c b/sound/soc/codecs/wm_adsp.c
>> index cef05d81c39b..6698b5343974 100644
>> --- a/sound/soc/codecs/wm_adsp.c
>> +++ b/sound/soc/codecs/wm_adsp.c
>> @@ -746,7 +746,6 @@ static void wm_adsp2_init_debugfs(struct wm_adsp *dsp,
>>  static void wm_adsp2_cleanup_debugfs(struct wm_adsp *dsp)
>>  {
>>  	wm_adsp_debugfs_clear(dsp);
>> -	debugfs_remove_recursive(dsp->debugfs_root);
>>  }
>
>It might be better not to backport this patch to the stable
>kernels. The issue has only been seen on one out of tree driver
>and the patch looks a little off to me. This
>debugfs_remove_recursive should run before the
>soc_cleanup_component_debugfs one, and as such it's hard to see
>what is actually going on. We are currently investigating internally
>but we might end up reverting the change, and it only seems to be
>causing issues on the one not upstreamed part.
>
>Apologies for missing the review of this one when it went up
>Mark, I was on holiday at the time.

I'll drop it, it didn't go anywhere yet :) Thanks!

-- 
Thanks,
Sasha