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>

diff --git a/drivers/watchdog/lpc18xx_wdt.c b/drivers/watchdog/lpc18xx_wdt.c
index 78cf11c949416786a3ca295a44d164e0b0ca7541..60b6d74f267dd67dbd89b5346f9711295c2e93c7 100644 (file)
--- a/drivers/watchdog/lpc18xx_wdt.c
+++ b/drivers/watchdog/lpc18xx_wdt.c
@@ -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;
 }

diff --git a/drivers/watchdog/w83877f_wdt.c b/drivers/watchdog/w83877f_wdt.c
index 6eb5185d6ea684d1debe40a6f4f45b91332924a2..d9addf06b44d643f05f446be9ec2f3ebab555def 100644 (file)
--- a/drivers/watchdog/w83877f_wdt.c
+++ b/drivers/watchdog/w83877f_wdt.c
@@ -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);