Re: [PATCH 03/20] ASoC: soc-component: move snd_soc_register_[un]component() to soc-component.c

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found no new issues
in this patch, but noticed 1 related pre-existing issue it does not
introduce:
- [Medium] ASoC: dmaengine: memory leak in
  snd_dmaengine_pcm_unregister() [1]
--

commit a5f7b09ef3fb2f0bb4b4617d3a6ce6f9faafae80
Author: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>

ASoC: soc-component: move snd_soc_register_[un]component() to soc-component.c

This commit moves component registration and unregistration functions and
their declarations from soc-core.c and soc.h to soc-component.c and
soc-component.h.

> diff --git a/sound/soc/soc-component.c b/sound/soc/soc-component.c
> index 6dad994009bdb..a2f079cd8aae2 100644
> --- a/sound/soc/soc-component.c
> +++ b/sound/soc/soc-component.c
> @@ -1549,3 +1549,217 @@ struct snd_soc_component *snd_soc_component_lookup_by_name(const char *component

[ ... ]

> +void snd_soc_unregister_component_by_driver(struct device *dev,
> +					    const struct snd_soc_component_driver *component_driver)
> +{
> +	const char *driver_name = NULL;
> +
> +	if (component_driver)
> +		driver_name = component_driver->name;
> +
> +	guard(mutex)(&client_mutex);
> +
> +	while (1) {
> +		struct snd_soc_component *component;
> +
> +		component = snd_soc_lookup_component_nolocked(dev, driver_name);
> +		if (!component)
> +			break;
> +
> +		snd_soc_del_component_unlocked(component);
> +	}
> +}

[Severity: Medium]
This problem wasn't introduced by this patch, but can this loop cause
snd_dmaengine_pcm_unregister() to leak dmaengine_pcm structures and DMA
channels [1] when a device registers multiple dmaengine PCMs?

sound/soc/soc-generic-dmaengine-pcm.c:snd_dmaengine_pcm_unregister() {
	component = snd_soc_lookup_component(dev, SND_DMAENGINE_PCM_DRV_NAME);
	if (!component)
		return;

	pcm = snd_soc_component_to_priv(component);

	snd_soc_unregister_component_by_driver(dev, component->driver);
	dmaengine_pcm_release_chan(pcm);
	kfree(pcm);
}

When devres releases multiple PCMs registered via
devm_snd_dmaengine_pcm_register() on the same device, the first call to
snd_dmaengine_pcm_unregister() removes all components matching
SND_DMAENGINE_PCM_DRV_NAME.  Subsequent release callbacks then get NULL
from snd_soc_lookup_component() and return early without releasing their
DMA channels or freeing their pcm structures.

[1] https://sashiko.dev/#/bug/linux-259df7eb-71d4-4d88-9686-fca9af84a4de

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/878q31nttj.wl-kuninori.morimoto.gx@renesas.com?part=3