watchdog: sc520_wdt: Fix possible use-after-free in wdt_turnoff()

[ Upstream commit 90b7c141132244e8e49a34a4c1e445cce33e07f4 ]

This module'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>
Link: https://lore.kernel.org/r/1620716691-108460-1-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/sc520_wdt.c b/drivers/watchdog/sc520_wdt.c
index 1cfd3f6a13d5f428adebe5a7b3e030b155f06a44..08500db8324f31922e8ea98abf21311f1b312e97 100644 (file)
--- a/drivers/watchdog/sc520_wdt.c
+++ b/drivers/watchdog/sc520_wdt.c
@@ -190,7 +190,7 @@ static int wdt_startup(void)
 static int wdt_turnoff(void)
 {
        /* Stop the timer */
-       del_timer(&timer);
+       del_timer_sync(&timer);
 
        /* Stop the watchdog */
        wdt_config(0);