linux-kernel - Re: [PATCH 1/4] ASoC: codec2codec: avoid invalid/double-free of pcm runtime

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Date:   Thu, 13 Feb 2020 09:37:18 +0100
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Samuel Holland <samuel@...lland.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, Jonathan Corbet <corbet@....net>
Cc:     alsa-devel@...a-project.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH 1/4] ASoC: codec2codec: avoid invalid/double-free of pcm runtime


On Thu 13 Feb 2020 at 07:11, Samuel Holland <samuel@...lland.org> wrote:

> The PCM runtime was freed during PMU in the case that the event hook
> encountered an error. However, it is also unconditionally freed during
> PMD. Avoid a double-free by dropping the call to kfree in the PMU
> hook.

Oh ... Thanks for finding this.

I thought that a widget which has failed PMU would not go through PMD,
but It seems the return value dapm_seq_check_event is not checked.

This brings another question/problem:
A link which has failed in PMU, could try in PMD to hw_free/shutdown a
dai which has not gone through startup/hw_params, right ?

>
> Fixes: a72706ed8208 ("ASoC: codec2codec: remove ephemeral variables")
> Cc: stable@...r.kernel.org
> Signed-off-by: Samuel Holland <samuel@...lland.org>
> ---
>  sound/soc/soc-dapm.c | 3 ---
>  1 file changed, 3 deletions(-)
>
> diff --git a/sound/soc/soc-dapm.c b/sound/soc/soc-dapm.c
> index b6378f025836..935b5375ecc5 100644
> --- a/sound/soc/soc-dapm.c
> +++ b/sound/soc/soc-dapm.c
> @@ -3888,9 +3888,6 @@ snd_soc_dai_link_event_pre_pmu(struct snd_soc_dapm_widget *w,
>  	runtime->rate = params_rate(params);
>  
>  out:
> -	if (ret < 0)
> -		kfree(runtime);
> -
>  	kfree(params);
>  	return ret;
>  }