linux-kernel - [PATCH] backlight: led_bl: Hold led_access lock when calling led_sysfs

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Message-ID: <20250122091914.309533-1-herve.codina@bootlin.com>
Date: Wed, 22 Jan 2025 10:19:14 +0100
From: Herve Codina <herve.codina@...tlin.com>
To: Lee Jones <lee@...nel.org>,
	Daniel Thompson <danielt@...nel.org>,
	Jingoo Han <jingoohan1@...il.com>,
	Helge Deller <deller@....de>,
	Tony Lindgren <tony@...mide.com>,
	Pavel Machek <pavel@....cz>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	Jean-Jacques Hiblot <jjhiblot@...com>
Cc: Daniel Thompson <daniel.thompson@...aro.org>,
	dri-devel@...ts.freedesktop.org,
	linux-fbdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Luca Ceresoli <luca.ceresoli@...tlin.com>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
	Herve Codina <herve.codina@...tlin.com>,
	stable@...r.kernel.org
Subject: [PATCH] backlight: led_bl: Hold led_access lock when calling led_sysfs_disable()

Lockdep detects the following issue on led-backlight removal:
  [  142.315935] ------------[ cut here ]------------
  [  142.315954] WARNING: CPU: 2 PID: 292 at drivers/leds/led-core.c:455 led_sysfs_enable+0x54/0x80
  ...
  [  142.500725] Call trace:
  [  142.503176]  led_sysfs_enable+0x54/0x80 (P)
  [  142.507370]  led_bl_remove+0x80/0xa8 [led_bl]
  [  142.511742]  platform_remove+0x30/0x58
  [  142.515501]  device_remove+0x54/0x90
  ...

Indeed, led_sysfs_enable() has to be called with the led_access
lock held.

Hold the lock when calling led_sysfs_disable().

Fixes: ae232e45acf9 ("backlight: add led-backlight driver")
Cc: stable@...r.kernel.org
Signed-off-by: Herve Codina <herve.codina@...tlin.com>
---
 drivers/video/backlight/led_bl.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/video/backlight/led_bl.c b/drivers/video/backlight/led_bl.c
index ae34d1ecbfbe..d2db157b2c29 100644
--- a/drivers/video/backlight/led_bl.c
+++ b/drivers/video/backlight/led_bl.c
@@ -229,8 +229,11 @@ static void led_bl_remove(struct platform_device *pdev)
 	backlight_device_unregister(bl);
 
 	led_bl_power_off(priv);
-	for (i = 0; i < priv->nb_leds; i++)
+	for (i = 0; i < priv->nb_leds; i++) {
+		mutex_lock(&priv->leds[i]->led_access);
 		led_sysfs_enable(priv->leds[i]);
+		mutex_unlock(&priv->leds[i]->led_access);
+	}
 }
 
 static const struct of_device_id led_bl_of_match[] = {
-- 
2.47.1