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 ab7b8b185d992e621a8644b1a7552cb81192dc1f..fbdc0f32e6663f92882b527b9930f0c0cc53f3d8 100644 (file)
--- a/drivers/watchdog/lpc18xx_wdt.c
+++ b/drivers/watchdog/lpc18xx_wdt.c
@@ -309,7 +309,7 @@ static int lpc18xx_wdt_remove(struct platform_device *pdev)
        unregister_restart_handler(&lpc18xx_wdt->restart_handler);
 
        dev_warn(&pdev->dev, "I quit now, hardware will probably reboot!\n");
-       del_timer(&lpc18xx_wdt->timer);
+       del_timer_sync(&lpc18xx_wdt->timer);
 
        watchdog_unregister_device(&lpc18xx_wdt->wdt_dev);
        clk_disable_unprepare(lpc18xx_wdt->wdt_clk);

diff --git a/drivers/watchdog/w83877f_wdt.c b/drivers/watchdog/w83877f_wdt.c
index f0483c75ed324b63cf3d63f33a2367325b1c7869..4b52cf321747ebe1d37c1e96d521e5c94fa0fc0c 100644 (file)
--- a/drivers/watchdog/w83877f_wdt.c
+++ b/drivers/watchdog/w83877f_wdt.c
@@ -170,7 +170,7 @@ static void wdt_startup(void)
 static void wdt_turnoff(void)
 {
        /* Stop the timer */
-       del_timer(&timer);
+       del_timer_sync(&timer);
 
        wdt_change(WDT_DISABLE);