Re: [alsa-devel] [PATCH] ASoC: core: Fix access to uninitialized list heads

[Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>]

On 12/4/19 9:14 AM, Takashi Iwai wrote:
> The error path of soc_new_pcm_runtime() invokes soc_free_pcm_runtime()
> that may cause a few problems.  First off, it calls list_del() for
> rtd->list that may not be initialized.  Similarly,
> snd_soc_pcm_component_free() traverses over the component list that
> may not be initialized, either.  Such access to the uninitialized list
> head would lead to either a BUG_ON() or a memory corruption.
> 
> This patch fixes the access to uninitialized list heads by
> initializing the list heads properly at the beginning before those
> error paths.
> 
> Signed-off-by: Takashi Iwai <tiwai@suse.de>

Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>

> ---
>   sound/soc/soc-core.c | 12 ++++++------
>   1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
> index 0e2e628302f1..726e5de850c4 100644
> --- a/sound/soc/soc-core.c
> +++ b/sound/soc/soc-core.c
> @@ -478,6 +478,12 @@ static struct snd_soc_pcm_runtime *soc_new_pcm_runtime(
>   		goto free_rtd;
>   
>   	rtd->dev = dev;
> +	INIT_LIST_HEAD(&rtd->list);
> +	INIT_LIST_HEAD(&rtd->component_list);
> +	INIT_LIST_HEAD(&rtd->dpcm[SNDRV_PCM_STREAM_PLAYBACK].be_clients);
> +	INIT_LIST_HEAD(&rtd->dpcm[SNDRV_PCM_STREAM_CAPTURE].be_clients);
> +	INIT_LIST_HEAD(&rtd->dpcm[SNDRV_PCM_STREAM_PLAYBACK].fe_clients);
> +	INIT_LIST_HEAD(&rtd->dpcm[SNDRV_PCM_STREAM_CAPTURE].fe_clients);
>   	dev_set_drvdata(dev, rtd);
>   	INIT_DELAYED_WORK(&rtd->delayed_work, close_delayed_work);
>   
> @@ -493,12 +499,6 @@ static struct snd_soc_pcm_runtime *soc_new_pcm_runtime(
>   	/*
>   	 * rtd remaining settings
>   	 */
> -	INIT_LIST_HEAD(&rtd->component_list);
> -	INIT_LIST_HEAD(&rtd->dpcm[SNDRV_PCM_STREAM_PLAYBACK].be_clients);
> -	INIT_LIST_HEAD(&rtd->dpcm[SNDRV_PCM_STREAM_CAPTURE].be_clients);
> -	INIT_LIST_HEAD(&rtd->dpcm[SNDRV_PCM_STREAM_PLAYBACK].fe_clients);
> -	INIT_LIST_HEAD(&rtd->dpcm[SNDRV_PCM_STREAM_CAPTURE].fe_clients);
> -
>   	rtd->card = card;
>   	rtd->dai_link = dai_link;
>   	if (!rtd->dai_link->ops)
> 
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