[PATCH] ASoC: dapm: remove widget from dirty list on free

[PATCH] ASoC: dapm: remove widget from dirty list on free

[Thomas Hebb]

A widget's "dirty" list_head, much like its "list" list_head, eventually
chains back to a list_head on the snd_soc_card itself. This means that
the list can stick around even after the widget (or all widgets) have
been freed. Currently, however, widgets that are in the dirty list when
freed remain there, corrupting the entire list and leading to memory
errors and undefined behavior when the list is next accessed or
modified.

I encountered this issue when a component failed to probe relatively
late in snd_soc_bind_card(), causing it to bail out and call
soc_cleanup_card_resources(), which eventually called
snd_soc_dapm_free() with widgets that were still dirty from when they'd
been added.

Fixes: db432b414e20 ("ASoC: Do DAPM power checks only for widgets changed since last run")
Cc: stable@vger.kernel.org
Signed-off-by: Thomas Hebb <tommyhebb@gmail.com>
---

 sound/soc/soc-dapm.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/sound/soc/soc-dapm.c b/sound/soc/soc-dapm.c
index 7f87b449f950..148c095df27b 100644
--- a/sound/soc/soc-dapm.c
+++ b/sound/soc/soc-dapm.c
@@ -2486,6 +2486,7 @@ void snd_soc_dapm_free_widget(struct snd_soc_dapm_widget *w)
 	enum snd_soc_dapm_direction dir;
 
 	list_del(&w->list);
+	list_del(&w->dirty);
 	/*
 	 * remove source and sink paths associated to this widget.
 	 * While removing the path, remove reference to it from both
-- 
2.29.2

Re: [PATCH] ASoC: dapm: remove widget from dirty list on free

[Charles Keepax]

On Sat, Dec 12, 2020 at 05:20:12PM -0800, Thomas Hebb wrote:
> A widget's "dirty" list_head, much like its "list" list_head, eventually
> chains back to a list_head on the snd_soc_card itself. This means that
> the list can stick around even after the widget (or all widgets) have
> been freed. Currently, however, widgets that are in the dirty list when
> freed remain there, corrupting the entire list and leading to memory
> errors and undefined behavior when the list is next accessed or
> modified.
> 
> I encountered this issue when a component failed to probe relatively
> late in snd_soc_bind_card(), causing it to bail out and call
> soc_cleanup_card_resources(), which eventually called
> snd_soc_dapm_free() with widgets that were still dirty from when they'd
> been added.
> 
> Fixes: db432b414e20 ("ASoC: Do DAPM power checks only for widgets changed since last run")
> Cc: stable@vger.kernel.org
> Signed-off-by: Thomas Hebb <tommyhebb@gmail.com>
> ---
> 
>  sound/soc/soc-dapm.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/sound/soc/soc-dapm.c b/sound/soc/soc-dapm.c
> index 7f87b449f950..148c095df27b 100644
> --- a/sound/soc/soc-dapm.c
> +++ b/sound/soc/soc-dapm.c
> @@ -2486,6 +2486,7 @@ void snd_soc_dapm_free_widget(struct snd_soc_dapm_widget *w)
>  	enum snd_soc_dapm_direction dir;
>  
>  	list_del(&w->list);
> +	list_del(&w->dirty);

I can't help but wonder if we should be taking the DAPM lock for
snd_soc_dapm_free_widgets. However your patch doesn't look like it
is making that any more scary and looks like we should be making
sure we remove the widget from the dirty list.

Reviewed-by: Charles Keepax <ckeepax@opensource.cirrus.com>

Thanks,
Charles

Re: [PATCH] ASoC: dapm: remove widget from dirty list on free

[Mark Brown]

On Sat, 12 Dec 2020 17:20:12 -0800, Thomas Hebb wrote:
> A widget's "dirty" list_head, much like its "list" list_head, eventually
> chains back to a list_head on the snd_soc_card itself. This means that
> the list can stick around even after the widget (or all widgets) have
> been freed. Currently, however, widgets that are in the dirty list when
> freed remain there, corrupting the entire list and leading to memory
> errors and undefined behavior when the list is next accessed or
> modified.
> 
> [...]

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git for-next

Thanks!

[1/1] ASoC: dapm: remove widget from dirty list on free
      commit: 5c6679b5cb120f07652418524ab186ac47680b49

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark