Re: [PATCH for-4.11] ASoC: don't dereference NULL pcm_{new,free}

From: Kuninori Morimoto
Date: Wed Mar 08 2017 - 19:24:14 EST



Hi Brian

Thank you for your patch

> Not all platform drivers have pcm_{new,free} callbacks. Seen with a
> "snd-soc-dummy" codec from sound/soc/rockchip/rk3399_gru_sound.c.
(snip)
> Fixes: 99b04f4c4051 ("ASoC: add Component level pcm_new/pcm_free")
> Signed-off-by: Brian Norris <briannorris@xxxxxxxxxxxx>
> ---
> I'm really not that familiar with this subsystem... but this does fix the
> crash seen here.
>
> sound/soc/soc-core.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
> index 6dca408faae3..2722bb0c5573 100644
> --- a/sound/soc/soc-core.c
> +++ b/sound/soc/soc-core.c
> @@ -3326,7 +3326,10 @@ static int snd_soc_platform_drv_pcm_new(struct snd_soc_pcm_runtime *rtd)
> {
> struct snd_soc_platform *platform = rtd->platform;
>
> - return platform->driver->pcm_new(rtd);
> + if (platform->driver->pcm_new)
> + return platform->driver->pcm_new(rtd);
> + else
> + return 0;
> }
>
> static void snd_soc_platform_drv_pcm_free(struct snd_pcm *pcm)
> @@ -3334,7 +3337,8 @@ static void snd_soc_platform_drv_pcm_free(struct snd_pcm *pcm)
> struct snd_soc_pcm_runtime *rtd = pcm->private_data;
> struct snd_soc_platform *platform = rtd->platform;
>
> - platform->driver->pcm_free(pcm);
> + if (platform->driver->pcm_free)
> + platform->driver->pcm_free(pcm);
> }

It is a littlle bit strange for me.
commit 99b04f4c4051 has below code. This means, if platform doesn't have pcm_new/free callback,
component doesn't have snd_soc_platform_drv_pcm_new/free.
But your case, platform doesn't have pcm_new/free, but component had it ?

...
@@ -3181,6 +3198,10 @@ int snd_soc_add_platform(struct device *dev, struct snd_soc_platform *platform,
platform->component.probe = snd_soc_platform_drv_probe;
if (platform_drv->remove)
platform->component.remove = snd_soc_platform_drv_remove;
+ if (platform_drv->pcm_new)
+ platform->component.pcm_new = snd_soc_platform_drv_pcm_new;
+ if (platform_drv->pcm_free)
+ platform->component.pcm_free = snd_soc_platform_drv_pcm_free;

#ifdef CONFIG_DEBUG_FS
platform->component.debugfs_prefix = "platform";