[PATCH v3 2/4] leds: trigger: netdev: Access net_dev under trigger_data->lock in the worker

[A. Sverdlin]

From: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxxxx>

netdev_trig_work() dereferences trigger_data->net_dev without the lock,
while set_device_name() and netdev_trig_notify() dev_put() and replace it
under trigger_data->lock.  On NETDEV_UNREGISTER the worker can run
dev_get_stats() on a netdev being freed (UAF).

Take trigger_data->lock in the worker.  cancel_delayed_work_sync() must
then never run under that lock.

Cc: stable@xxxxxxxxxxxxxxx
Closes: https://lore.kernel.org/all/20260914142116.6DAC51F000FF@xxxxxxxxxxxxxxx/
Fixes: 06f502f57d0d ("leds: trigger: Introduce a NETDEV trigger")
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxxxx>
---
Changelog:
v3:
- explicit mutex_lock()/mutex_unlock() instead of guard()

 drivers/leds/trigger/ledtrig-netdev.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/leds/trigger/ledtrig-netdev.c b/drivers/leds/trigger/ledtrig-netdev.c
index e2a6c95a0dc97..d62a7b0168523 100644
--- a/drivers/leds/trigger/ledtrig-netdev.c
+++ b/drivers/leds/trigger/ledtrig-netdev.c
@@ -683,9 +683,12 @@ static void netdev_trig_work(struct work_struct *work)
 	unsigned long interval;
 	int invert;
 
+	mutex_lock(&trigger_data->lock);
+
 	/* If we dont have a device, insure we are off */
 	if (!trigger_data->net_dev) {
 		led_set_brightness(trigger_data->led_cdev, LED_OFF);
+		mutex_unlock(&trigger_data->lock);
 		return;
 	}
 
@@ -693,8 +696,10 @@ static void netdev_trig_work(struct work_struct *work)
 	if (!test_bit(TRIGGER_NETDEV_TX, &trigger_data->mode) &&
 	    !test_bit(TRIGGER_NETDEV_RX, &trigger_data->mode) &&
 	    !test_bit(TRIGGER_NETDEV_TX_ERR, &trigger_data->mode) &&
-	    !test_bit(TRIGGER_NETDEV_RX_ERR, &trigger_data->mode))
+	    !test_bit(TRIGGER_NETDEV_RX_ERR, &trigger_data->mode)) {
+		mutex_unlock(&trigger_data->lock);
 		return;
+	}
 
 	dev_stats = dev_get_stats(trigger_data->net_dev, &temp);
 	new_activity =
@@ -735,6 +740,8 @@ static void netdev_trig_work(struct work_struct *work)
 
 	schedule_delayed_work(&trigger_data->work,
 			(atomic_read(&trigger_data->interval)*2));
+
+	mutex_unlock(&trigger_data->lock);
 }
 
 static int netdev_trig_activate(struct led_classdev *led_cdev)
-- 
2.55.0