linux-kernel - Re: [PATCH] ALSA: hda/realtek: Fix resource cleanup in alc_alloc

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Message-ID: <87pl9qxq23.wl-tiwai@suse.de>
Date: Mon, 10 Nov 2025 09:14:12 +0100
From: Takashi Iwai <tiwai@...e.de>
To: wangdich9700@....com
Cc: lgirdwood@...il.com,
	broonie@...nel.org,
	perex@...ex.cz,
	tiwai@...e.com,
	cezary.rojewski@...el.com,
	linux-kernel@...r.kernel.org,
	linux-sound@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	wangdicheng <wangdicheng@...inos.cn>
Subject: Re: [PATCH] ALSA: hda/realtek: Fix resource cleanup in alc_alloc_spec error path

On Mon, 10 Nov 2025 08:23:49 +0100,
wangdich9700@....com wrote:
> 
> From: wangdicheng <wangdicheng@...inos.cn>
> 
> Ensure proper resource cleanup when alc_codec_rename_from_preset() fails
> in alc_alloc_spec(). Currently, the error path only calls kfree(spec) but
> does not:
> 
> 1. Destroy the initialized coef_mutex mutex

It's rather an optional operation.  As of the probing phase, there is
really no much race, after all.
(And, it's not handled properly in your patch, either...)

> 2. Reset codec->spec to NULL, potentially leaving a dangling pointer

This is done in snd_hda_codec_cleanup_for_unbind() called in the error
handling of hda_codec_driver_probe().


thanks,

Takashi

> 
> Signed-off-by: wangdicheng <wangdicheng@...inos.cn>
> ---
>  sound/hda/codecs/realtek/realtek.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/sound/hda/codecs/realtek/realtek.c b/sound/hda/codecs/realtek/realtek.c
> index ca377a5adadb..9a358c072e50 100644
> --- a/sound/hda/codecs/realtek/realtek.c
> +++ b/sound/hda/codecs/realtek/realtek.c
> @@ -1029,6 +1029,7 @@ int alc_alloc_spec(struct hda_codec *codec, hda_nid_t mixer_nid)
>  {
>  	struct alc_spec *spec = kzalloc(sizeof(*spec), GFP_KERNEL);
>  	int err;
> +	bool mutex_initialized = false;
>  
>  	if (!spec)
>  		return -ENOMEM;
> @@ -1040,14 +1041,22 @@ int alc_alloc_spec(struct hda_codec *codec, hda_nid_t mixer_nid)
>  	/* FIXME: do we need this for all Realtek codec models? */
>  	codec->spdif_status_reset = 1;
>  	codec->forced_resume = 1;
> +
>  	mutex_init(&spec->coef_mutex);
>  
>  	err = alc_codec_rename_from_preset(codec);
>  	if (err < 0) {
> -		kfree(spec);
> -		return err;
> +		codec_err(codec, "Failed to rename codec: %d\n", err);
> +		goto error;
>  	}
>  	return 0;
> +
> +error:
> +	if (mutex_initialized)
> +		mutex_destroy(&spec->coef_mutex);
> +	codec->spec = NULL;
> +	kfree(spec);
> +	return err;
>  }
>  EXPORT_SYMBOL_NS_GPL(alc_alloc_spec, "SND_HDA_CODEC_REALTEK");
>  
> -- 
> 2.25.1
>