[PATCH 4.19 482/639] PM: sleep: Fix possible overflow in pm_system_cancel_wakeup()

[Greg Kroah-Hartman]

From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>

[ Upstream commit 2933954b71f10d392764f95eec0f0aa2d103054b ]

It is not actually guaranteed that pm_abort_suspend will be
nonzero when pm_system_cancel_wakeup() is called which may lead to
subtle issues, so make it use atomic_dec_if_positive() instead of
atomic_dec() for the safety sake.

Fixes: 33e4f80ee69b ("ACPI / PM: Ignore spurious SCI wakeups from suspend-to-idle")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Acked-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/base/power/wakeup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/base/power/wakeup.c b/drivers/base/power/wakeup.c
index 7c84f64c74f77..2dfa2e0487451 100644
--- a/drivers/base/power/wakeup.c
+++ b/drivers/base/power/wakeup.c
@@ -875,7 +875,7 @@ EXPORT_SYMBOL_GPL(pm_system_wakeup);
 
 void pm_system_cancel_wakeup(void)
 {
-	atomic_dec(&pm_abort_suspend);
+	atomic_dec_if_positive(&pm_abort_suspend);
 }
 
 void pm_wakeup_clear(bool reset)
-- 
2.20.1