[PATCH v6 01/12] leds: class: Always protect brightness_show() with led_access

[Rong Zhang <i@rong.moe>]

The led_classdev_register_ext() protects transient states when
registering with the led_access mutex and relies on all sensitive sysfs
attribute callbacks holding the mutex to prevent exposing transient
states.

The Fixes: commit broke this as it accessed trigger_lock without holding
led_access. Fix it by protecting brightness_show() with led_access in
all code paths.

Fixes: b819dc7d8fb2 ("leds: core: Report ENODATA for brightness of hardware controlled LED")
Signed-off-by: Rong Zhang <i@rong.moe>
---
Changes in v6:
- New patch in the series to address a concern from Sashiko
  - https://sashiko.dev/#/patchset/20260821-leds-trigger-hw-changed-v5-0-3e00d6c4a936@rong.moe?part=7
---
 drivers/leds/led-class.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index a51b0ed53886..4259533dafa1 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -43,13 +43,13 @@ static ssize_t brightness_show(struct device *dev,
 	struct led_classdev *led_cdev = dev_get_drvdata(dev);
 	unsigned int brightness;
 
-	if (led_trigger_is_hw_controlled(led_cdev))
-		return -ENODATA;
+	scoped_guard(mutex, &led_cdev->led_access) {
+		if (led_trigger_is_hw_controlled(led_cdev))
+			return -ENODATA;
 
-	mutex_lock(&led_cdev->led_access);
-	led_update_brightness(led_cdev);
-	brightness = led_cdev->brightness;
-	mutex_unlock(&led_cdev->led_access);
+		led_update_brightness(led_cdev);
+		brightness = led_cdev->brightness;
+	}
 
 	return sysfs_emit(buf, "%u\n", brightness);
 }

-- 
2.55.0