From: Zou Wei zou_wei@huawei.com

stable inclusion from stable-v4.19.198 commit ecd620e0fb1ff7f78fdb593379b2e6938c99707a category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9RL1P CVE: CVE-2021-47321

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...

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[ 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.c... 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 Signed-off-by: Jialin Zhang zhangjialin11@huawei.com --- drivers/watchdog/lpc18xx_wdt.c | 2 +- drivers/watchdog/w83877f_wdt.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/watchdog/lpc18xx_wdt.c b/drivers/watchdog/lpc18xx_wdt.c index 331cadb459ac..48580b6406c2 100644 --- 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 05658ecc0aa4..ec4641fc2d21 100644 --- 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);