Commit 953b9dd7 authored Aug 28, 2018 by Wolfram Sang Committed by Wim Van Sebroeck Oct 02, 2018

watchdog: core: fix null pointer dereference when releasing cdev



watchdog_stop() calls watchdog_update_worker() which needs a valid
wdd->wd_data pointer. So, when unregistering the cdev, clear the
pointers after we call watchdog_stop(), not before.

Fixes: bb292ac1 ("watchdog: Introduce watchdog_stop_on_unregister helper")
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

parent 3bed02a2

drivers/watchdog/watchdog_dev.c

+5 −5

Original line number	Diff line number	Diff line
		@@ -1019,16 +1019,16 @@ static void watchdog_cdev_unregister(struct watchdog_device *wdd)
		old_wd_data = NULL;
		}

		mutex_lock(&wd_data->lock);
		wd_data->wdd = NULL;
		wdd->wd_data = NULL;
		mutex_unlock(&wd_data->lock);

		if (watchdog_active(wdd) &&
		test_bit(WDOG_STOP_ON_UNREGISTER, &wdd->status)) {
		watchdog_stop(wdd);
		}

		mutex_lock(&wd_data->lock);
		wd_data->wdd = NULL;
		wdd->wd_data = NULL;
		mutex_unlock(&wd_data->lock);

		hrtimer_cancel(&wd_data->timer);
		kthread_cancel_work_sync(&wd_data->work);

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