Re: [PATCH v8 01/14] Revert "backlight: Remove notifier"

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Uninitialized `backlight_notifier` rwsem leads to kernel panic on registration if `backlight_class_init()` fails.
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commit d337f12d53eda5facdddbe940d5c74c91750178b
Author: Mario Limonciello <mario.limonciello@amd.com>

Revert "backlight: Remove notifier"

This commit reverts the removal of the backlight notifier support, as it
is needed to add backlight control support into DRM connectors.

> diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
> index fc9bb303e8c5f..4401f6294ccc8 100644
> --- a/drivers/video/backlight/backlight.c
> +++ b/drivers/video/backlight/backlight.c
> @@ -65,6 +65,7 @@
>  
>  static struct list_head backlight_dev_list;
>  static struct mutex backlight_dev_list_mutex;
> +static struct blocking_notifier_head backlight_notifier;

[Severity: High]
Does this zero-initialized notifier head lead to a kernel panic if
backlight_class_init() in drivers/video/backlight/backlight.c fails?

If class_register() fails in backlight_class_init() due to memory pressure
or sysfs issues, the function will return early and skip the dynamic
initialization via BLOCKING_INIT_NOTIFIER_HEAD().

When a subsequent caller calls backlight_register_notifier(), it will pass
this zero-initialized notifier to blocking_notifier_chain_register(), which
will attempt to lock the uninitialized rw_semaphore and cause an oops.

Could this be prevented by using the static initialization macro instead?

static BLOCKING_NOTIFIER_HEAD(backlight_notifier);

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Sashiko AI review · https://sashiko.dev/#/patchset/20260908044035.62093-1-mario.limonciello@amd.com?part=1