Commit db222f14 authored May 12, 2021 by Zou Wei Committed by Greg Kroah-Hartman Jul 20, 2021

watchdog: Fix possible use-after-free by calling del_timer_sync()



[ Upstream commit d0212f095ab56672f6f36aabc605bda205e1e0bf ]

This driver's remove path calls del_timer(). However, that function
does not wait until the timer handler finishes. This means that the
timer handler may still be running after the driver's remove function
has finished, which would result in a use-after-free.

Fix by calling del_timer_sync(), which makes sure the timer handler
has finished, and unable to re-schedule itself.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zou Wei <zou_wei@huawei.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Vladimir Zapolskiy <vz@mleia.com>
Link: https://lore.kernel.org/r/1620802676-19701-1-git-send-email-zou_wei@huawei.com


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>

parent 7c56c550

drivers/watchdog/lpc18xx_wdt.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -292,7 +292,7 @@ static int lpc18xx_wdt_remove(struct platform_device *pdev)
		struct lpc18xx_wdt_dev *lpc18xx_wdt = platform_get_drvdata(pdev);

		dev_warn(&pdev->dev, "I quit now, hardware will probably reboot!\n");
		del_timer(&lpc18xx_wdt->timer);
		del_timer_sync(&lpc18xx_wdt->timer);

		return 0;
		}

drivers/watchdog/w83877f_wdt.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -166,7 +166,7 @@ static void wdt_startup(void)
		static void wdt_turnoff(void)
		{
		/* Stop the timer */
		del_timer(&timer);
		del_timer_sync(&timer);

		wdt_change(WDT_DISABLE);