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[4.19,364/421] watchdog: Fix possible use-after-free in wdt_startup()

Message ID 20210719144958.870147710@linuxfoundation.org
State Superseded
Headers show
Series None | expand

Commit Message

Greg Kroah-Hartman July 19, 2021, 2:52 p.m. UTC 
From: Zou Wei <zou_wei@huawei.com>

[ Upstream commit c08a6b31e4917034f0ed0cb457c3bb209576f542 ]

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/1620716495-108352-1-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>
---
 drivers/watchdog/sbc60xxwdt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
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Patch

diff --git a/drivers/watchdog/sbc60xxwdt.c b/drivers/watchdog/sbc60xxwdt.c
index 87333a41f753..1702df7f8c38 100644
--- a/drivers/watchdog/sbc60xxwdt.c
+++ b/drivers/watchdog/sbc60xxwdt.c
@@ -152,7 +152,7 @@  static void wdt_startup(void)
 static void wdt_turnoff(void)
 {
 	/* Stop the timer */
-	del_timer(&timer);
+	del_timer_sync(&timer);
 	inb_p(wdt_stop);
 	pr_info("Watchdog timer is now disabled...\n");
 }