| From | Sasha Levin <> | Subject | [PATCH AUTOSEL 4.19 038/209] watchdog: core: fix null pointer dereference when releasing cdev | Date | Tue, 12 Nov 2019 20:47:34 -0500 |
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From: Wolfram Sang <wsa+renesas@sang-engineering.com>
[ Upstream commit 953b9dd7725bad55a922a35e75bff7bebf7b9978 ]
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: bb292ac1c602 ("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> Signed-off-by: Sasha Levin <sashal@kernel.org> --- drivers/watchdog/watchdog_dev.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c index ffbdc4642ea55..f6c24b22b37c0 100644 --- a/drivers/watchdog/watchdog_dev.c +++ b/drivers/watchdog/watchdog_dev.c @@ -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); -- 2.20.1
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