[PATCH 4/8] PM: sleep: Fix possible overflow in pm_system_cancel_wakeup()

From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Linux PM <linux-pm@vger.kernel.org>
Cc: Linux ACPI <linux-acpi@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Len Brown <len.brown@intel.com>,
	Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Rajneesh Bhardwaj <rajneesh.bhardwaj@linux.intel.com>,
	"David E. Box" <david.e.box@linux.intel.com>
Subject: [PATCH 4/8] PM: sleep: Fix possible overflow in pm_system_cancel_wakeup()
Date: Tue, 16 Jul 2019 18:14:58 +0200	[thread overview]
Message-ID: <2970489.lynJ6BP8VZ@kreacher> (raw)
In-Reply-To: <71085220.z6FKkvYQPX@kreacher>

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

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>
---
 drivers/base/power/wakeup.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-pm/drivers/base/power/wakeup.c
===================================================================

--- linux-pm.orig/drivers/base/power/wakeup.c
+++ linux-pm/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)



