[alsa-devel] [PATCH] ASoC: dapm: Fix widget double free with auto-disable DAPM kcontrol

[Lars-Peter Clausen]

On 04/15/2014 03:58 PM, Jarkko Nikula wrote:
> Commit 9e1fda4ae158 ("ASoC: dapm: Implement mixer input auto-disable") is trying to
> free the widget it allocated by snd_soc_dapm_new_control() call in
> dapm_kcontrol_data_alloc() by adding kfree(data->widget) to dapm_kcontrol_free().
>
> This is causing a widget double free with auto-disabled DAPM kcontrols in sound card
> unregistration because widgets are already freed before dapm_kcontrol_free() is
> called.
>
> Reason for that is all widgets are added into dapm->card->widgets list in
> snd_soc_dapm_new_control() and freed in dapm_free_widgets() during execution of
> snd_soc_dapm_free().
>
> Now snd_soc_dapm_free() calls for different DAPM contexts happens before
> snd_card_free() call from where the call chain to dapm_kcontrol_free() begins:
>
> soc_cleanup_card_resources()
>    soc_remove_dai_links()
>      soc_remove_link_dais()
>        snd_soc_dapm_free(&cpu_dai->dapm)
>      soc_remove_link_components()
>        soc_remove_platform()
>          snd_soc_dapm_free(&platform->dapm)
>        soc_remove_codec()
>          snd_soc_dapm_free(&codec->dapm)
>    snd_soc_dapm_free(&card->dapm)
>    snd_card_free()
>      snd_card_do_free()
>        snd_device_free_all()
>          snd_device_free()
>            snd_ctl_dev_free()
>              snd_ctl_remove()
>                snd_ctl_free_one()
>                  dapm_kcontrol_free()
>
> This wasn't making harm with ordinary DAPM kcontrols since data->widget is NULL for
> them.
>
> Signed-off-by: Jarkko Nikula <jarkko.nikula at linux.intel.com>
> Cc: stable <stable at vger.kernel.org> # 3.12+

Acked-by: Lars-Peter Clausen <lars at metafoo.de>

Thanks.

> ---
>   sound/soc/soc-dapm.c | 1 -
>   1 file changed, 1 deletion(-)
>
> diff --git a/sound/soc/soc-dapm.c b/sound/soc/soc-dapm.c
> index c8a780d0d057..7769b0a2bc5a 100644
> --- a/sound/soc/soc-dapm.c
> +++ b/sound/soc/soc-dapm.c
> @@ -254,7 +254,6 @@ static int dapm_kcontrol_data_alloc(struct snd_soc_dapm_widget *widget,
>   static void dapm_kcontrol_free(struct snd_kcontrol *kctl)
>   {
>   	struct dapm_kcontrol_data *data = snd_kcontrol_chip(kctl);
> -	kfree(data->widget);
>   	kfree(data->wlist);
>   	kfree(data);
>   }
>