In the Linux kernel, the following vulnerability has been resolved:

watchdog: unregister PM notifier on watchdog unregister

watchdog_register_device() registers wdd->pm_nb when
WDOG_NO_PING_ON_SUSPEND is set, but watchdog_unregister_device() does not
remove it. This leaves an embedded notifier block on the PM notifier chain
after the watchdog device has been unregistered.

A later suspend/resume notification can then call watchdog_pm_notifier()
with a stale watchdog_device pointer, or at minimum after wdd->wd_data has
been cleared by watchdog_dev_unregister().

Unregister the PM notifier before tearing down the watchdog device.