PM: sleep: Fix possible overflow in pm_system_cancel_wakeup()

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@intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/drivers/base/power/wakeup.c b/drivers/base/power/wakeup.c
index ee31d4f8d856ed486bb5612b940994e4bb60c7be..b30c45aad10f1b35dfa4a7a7c8b13c7f78ac857e 100644 (file)
--- a/drivers/base/power/wakeup.c
+++ b/drivers/base/power/wakeup.c
@@ -859,7 +859,7 @@ 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)