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From: Arnaud Pouliquen <arnaud.pouliquen@st.com>
To: Rohit Kumar <rohitkr@codeaurora.org>,
	Takashi Iwai <tiwai@suse.de>, <olivier.moysan@st.com>
Cc: <rohkumar@qti.qualcomm.com>, <alsa-devel@alsa-project.org>,
	<bgoswami@codeaurora.org>, <linux-kernel@vger.kernel.org>,
	<plai@codeaurora.org>, <tiwai@suse.com>, <lgirdwood@gmail.com>,
	<broonie@kernel.org>, <srinivas.kandagatla@linaro.org>
Subject: Re: [alsa-devel] [PATCH] ASoC: core: Invoke pcm_new() for all DAI-link
Date: Mon, 5 Nov 2018 12:13:20 +0100	[thread overview]
Message-ID: <791d4587-4db3-3ffa-331a-f79d0993ca8c@st.com> (raw)
In-Reply-To: <48c78f67-8178-2d07-e35d-2e4eca51ccbc@codeaurora.org>

Hello Rohit,

On 11/2/18 1:06 PM, Rohit Kumar wrote:
> 
> On 11/2/2018 1:12 PM, Takashi Iwai wrote:
>> On Thu, 01 Nov 2018 13:38:49 +0100,
>> Rohit kumar wrote:
>>> Remove no_pcm check to invoke pcm_new() for backend dai-links
>>> too. This fixes crash in hdmi codec driver during hdmi_codec_startup()
>>> while accessing chmap_info struct. chmap_info struct memory is
>>> allocated in pcm_new() of hdmi codec driver which is not invoked
>>> in case of DPCM when hdmi codec driver is part of backend dai-link.
>>>
>>> Below is the crash stack:
>>>
>>> [   61.635493] Unable to handle kernel NULL pointer dereference at
>>> virtual address 00000018
>>> ..
>>> [   61.666696]   CM = 0, WnR = 1
>>> [   61.669778] user pgtable: 4k pages, 39-bit VAs, pgd =
>>> ffffffc0d6633000
>>> [   61.676526] [0000000000000018] *pgd=0000000153fc8003,
>>> *pud=0000000153fc8003, *pmd=0000000000000000
>>> [   61.685793] Internal error: Oops: 96000046 [#1] PREEMPT SMP
>>> [   61.722955] CPU: 7 PID: 2238 Comm: aplay Not tainted 4.14.72 #21
>>> ..
>>> [   61.740269] PC is at hdmi_codec_startup+0x124/0x164
>>> [   61.745308] LR is at hdmi_codec_startup+0xe4/0x164
>>>
>>> Signed-off-by: Rohit kumar <rohitkr@codeaurora.org>
>> Did you check whether all drivers have no side-effect by this change?
>> The hdmi-codec isn't the only driver that has pcm_new ops, so we have
>> to make sure that such a fundamental change wouldn't bring any
>> regressions.
>>
> Below are the drivers calling pcm_new() other than hdmi codec driver.
> sound/soc/meson/axg-frddr.c
> sound/soc/meson/axg-toddr.c
> These two drivers are frontend DAI drivers and should not be impacted
> because of this.
> 
> Other than this, pcm_new() is called from sound/soc/stm/stm32_sai_sub.c
> I could not get much info about this driver. However, it is just adding
> kcontrols in pcm_new() which uses internal private structs in get()/put().
> Olivier Moysan can too confirm on this.
First, i'm answering  for Olivier: no regression identified for the SAI
driver, it is not a DPCM driver.

Then i have a concern about the call of pcm_new for a no-PCM backend.
Does it make sense? In DPCM concept, the backend is not linked to the
PCM device...

Instead, I would suggest that you add protection in HDMI_codec on
chmap_info pointer.

The drawback would be that the control is no more available...do you
need it?

Regards
Arnaud

> 
> Thanks,
> Rohit
>> thanks,
>>
>> Takashi
> 

  reply	other threads:[~2018-11-05 11:13 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-01 12:38 Rohit kumar
2018-11-02  7:42 ` [alsa-devel] " Takashi Iwai
2018-11-02 12:06   ` Rohit Kumar
2018-11-05 11:13     ` Arnaud Pouliquen [this message]
2018-11-05 18:14       ` Rohit Kumar
2018-11-06 15:41         ` Arnaud Pouliquen
2018-11-07 16:14           ` Mark Brown
2018-12-13 18:10 ` Applied "ASoC: core: Invoke pcm_new() for all DAI-link" to the asoc tree Mark Brown

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