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 331cadb459ac5da03c6f4c5fb74d7266c337e446..48580b6406c251b4857f84bc3c3944bc7349cdd3 100644 (file)
--- a/drivers/watchdog/lpc18xx_wdt.c
+++ b/drivers/watchdog/lpc18xx_wdt.c
@@ -301,7 +301,7 @@ 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);
 
        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 05658ecc0aa4cdc87875ec05aba6eed23b4f1551..ec4641fc2d211422e2cbb765f804850261dae81b 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);