watchdog: cpu5wdt.c: Fix use-after-free bug caused by cpu5wdt_trigger

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: watchdog: cpu5wdt.c: Fix use-after-free bug caused by cpu5wdt_trigger When the cpu5wdt module is removing, the origin code uses del_timer() to de-activate the timer. If the timer handler is running, del_timer() could not stop it and will return directly. If the port region is released by release_region() and then the timer handler cpu5wdt_trigger() calls outb() to write into the region that is released, the use-after-free bug will happen. Change del_timer() to timer_shutdown_sync() in order that the timer handler could be finished before the port region is released.

References

• https://git.kernel.org/stable/c/9b1c063ffc075abf56f63e55d70b9778ff534314
• https://git.kernel.org/stable/c/f19686d616500cd0d47b30cee82392b53f7f784a
• https://git.kernel.org/stable/c/573601521277119f2e2ba5f28ae6e87fc594f4d4