linux-kernel - Re: [alsa-devel] [PATCH] ASoC: core: Invoke pcm

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Date:   Fri, 02 Nov 2018 08:42:10 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     Rohit kumar <rohitkr@...eaurora.org>
Cc:     plai@...eaurora.org, bgoswami@...eaurora.org, lgirdwood@...il.com,
        broonie@...nel.org, perex@...ex.cz, tiwai@...e.com,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        rohkumar@....qualcomm.com, srinivas.kandagatla@...aro.org
Subject: Re: [alsa-devel] [PATCH] ASoC: core: Invoke pcm_new() for all DAI-link

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@...eaurora.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.


thanks,

Takashi