Re: [alsa-devel] [PATCH v2 3/3] ASoC: topology: Prevent use-after-free in snd_soc_get_pcm_runtime()

From: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
To: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Cc: tiwai@suse.de, Dragos Tarcatu <dragos_tarcatu@mentor.com>,
	alsa-devel@alsa-project.org, broonie@kernel.org,
	Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Subject: Re: [alsa-devel] [PATCH v2 3/3] ASoC: topology: Prevent use-after-free in snd_soc_get_pcm_runtime()
Date: 18 Dec 2019 10:57:49 +0900	[thread overview]
Message-ID: <87v9qejsyq.wl-kuninori.morimoto.gx@renesas.com> (raw)
In-Reply-To: <20191218000518.5830-4-pierre-louis.bossart@linux.intel.com>


Hi Pierre-Louis

> From: Dragos Tarcatu <dragos_tarcatu@mentor.com>
> 
> remove_link() is currently calling snd_soc_remove_pcm_runtime() after
> it has already freed the memory for the link name. But this is later
> read from snd_soc_get_pcm_runtime() causing a KASAN use-after-free
> warning. Reorder the cleanups to fix this issue.
> 
> Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
> Signed-off-by: Dragos Tarcatu <dragos_tarcatu@mentor.com>
> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
> ---
>  sound/soc/soc-topology.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/sound/soc/soc-topology.c b/sound/soc/soc-topology.c
> index f8bd406c6198..2b3c74a0b126 100644
> --- a/sound/soc/soc-topology.c
> +++ b/sound/soc/soc-topology.c
> @@ -548,14 +548,14 @@ static void remove_link(struct snd_soc_component *comp,
>  	if (dobj->ops && dobj->ops->link_unload)
>  		dobj->ops->link_unload(comp, dobj);
>  
> -	kfree(link->name);
> -	kfree(link->stream_name);
> -	kfree(link->cpus->dai_name);
> -
>  	list_del(&dobj->list);
>  
>  	snd_soc_remove_pcm_runtime(comp->card,
>  			snd_soc_get_pcm_runtime(comp->card, link));
> +
> +	kfree(link->name);
> +	kfree(link->stream_name);
> +	kfree(link->cpus->dai_name);
>  	kfree(link);
>  }

Acked-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>

Thank you for your help !!
Best regards
---
Kuninori Morimoto
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