linux-kernel - Re: [PATCH for-4.11] ASoC: don't dereference NULL pcm

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Message-ID: <20170311003939.GB4586@google.com>
Date:   Fri, 10 Mar 2017 16:39:39 -0800
From:   Brian Norris <briannorris@...omium.org>
To:     Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
Cc:     Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>, linux-kernel@...r.kernel.org,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, alsa-devel@...a-project.org
Subject: Re: [PATCH for-4.11] ASoC: don't dereference NULL pcm_{new,free}

Hi Kuninori,

On Thu, Mar 09, 2017 at 12:53:50AM +0000, Kuninori Morimoto wrote:
> > All I know is that I'm definitely hitting a NULL
> > platform->driver->pcm_new callback, and that either reverting your patch
> > or applying the patch I just sent fixes it.
> 
> I want to know why this happen.
> Can you show me which driver is calling snd_soc_add_platform() in your case ?

There are 4 drivers calling that:

  snd_soc_dummy_probe
  rt5514_spi_probe
  2 instances of snd_dmaengine_pcm_register, via rockchip_i2s_probe

Only the latter two seem to run the assignment here:

	if (platform_drv->pcm_new)
		platform->component.pcm_new = snd_soc_platform_drv_pcm_new;

Both snd_soc_dummy_probe and rt5514_spi_probe find ->pcm_new NULL here.

I'm running with the sound/soc/rockchip/rk3399_gru_sound.c platform
driver. If it helps, I'm using the DT posted at [1]. IIUC, the "RT5514
DSP" link is trying to link up a "snd-soc-dummy" instance.

I'm fairly thoroughly confused. Any better ideas?

Brian

[1] https://www.spinics.net/lists/arm-kernel/msg561964.html
    [PATCH v2 4/6] arm64: dts: rockchip: add Gru/Kevin DTS