From b0142d66f4edb8578b7772d6d7ad731836b82ddb Mon Sep 17 00:00:00 2001
From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Date: Tue, 10 Dec 2019 12:48:35 +0100
Subject: [PATCH] cpuidle: Fix cpuidle_driver_state_disabled()
Git-commit: b0142d66f4edb8578b7772d6d7ad731836b82ddb
Patch-mainline: v5.5-rc2
References: bsc#1175543

It turns out that cpuidle_driver_state_disabled() can be called
before registering the cpufreq driver on some platforms, which
was not expected when it was introduced and which leads to a NULL
pointer dereference when trying to walk the CPUs associated with
the given cpuidle driver.

Fix the problem by making cpuidle_driver_state_disabled() check if
the driver's mask of CPUs associated with it is present and to set
CPUIDLE_FLAG_UNUSABLE for the given idle state in the driver's states
list if that is not the case to cause __cpuidle_register_device() to
set CPUIDLE_STATE_DISABLED_BY_DRIVER for that state for all cpuidle
devices registered by it later.

Fixes: cbda56d5fefc ("cpuidle: Introduce cpuidle_driver_state_disabled() for driver quirks")
Reported-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Tested-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Lin Ma <lma@suse.com>
---
 drivers/cpuidle/driver.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/cpuidle/driver.c b/drivers/cpuidle/driver.c
index fb904ff05256..146ca62e330d 100644
--- a/drivers/cpuidle/driver.c
+++ b/drivers/cpuidle/driver.c
@@ -392,6 +392,13 @@ void cpuidle_driver_state_disabled(struct cpuidle_driver *drv, int idx,
 
 	mutex_lock(&cpuidle_lock);
 
+	spin_lock(&cpuidle_driver_lock);
+
+	if (!drv->cpumask) {
+		drv->states[idx].flags |= CPUIDLE_FLAG_UNUSABLE;
+		goto unlock;
+	}
+
 	for_each_cpu(cpu, drv->cpumask) {
 		struct cpuidle_device *dev = per_cpu(cpuidle_devices, cpu);
 
@@ -404,5 +411,8 @@ void cpuidle_driver_state_disabled(struct cpuidle_driver *drv, int idx,
 			dev->states_usage[idx].disable &= ~CPUIDLE_STATE_DISABLED_BY_DRIVER;
 	}
 
+unlock:
+	spin_unlock(&cpuidle_driver_lock);
+
 	mutex_unlock(&cpuidle_lock);
 }
-- 
2.26.2