From: Richard Cochran <rcochran@linutronix.de>
Date: Fri, 11 Mar 2016 08:43:07 +0000 (+0100)
Subject: cpufreq: Make cpufreq_quick_get() safe to call
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=c75361c0b08a59d3c9863a5a673ae039d5118c35;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git

cpufreq: Make cpufreq_quick_get() safe to call

The function, cpufreq_quick_get, accesses the global 'cpufreq_driver' and
its fields without taking the associated lock, cpufreq_driver_lock.

Without the locking, nothing guarantees that 'cpufreq_driver' remains
consistent during the call.  This patch fixes the issue by taking the lock
before accessing the data structure.

Signed-off-by: Richard Cochran <rcochran@linutronix.de>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 4c7825856eab..f870399f00b1 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1401,9 +1401,17 @@ unsigned int cpufreq_quick_get(unsigned int cpu)
 {
 	struct cpufreq_policy *policy;
 	unsigned int ret_freq = 0;
+	unsigned long flags;
 
-	if (cpufreq_driver && cpufreq_driver->setpolicy && cpufreq_driver->get)
-		return cpufreq_driver->get(cpu);
+	read_lock_irqsave(&cpufreq_driver_lock, flags);
+
+	if (cpufreq_driver && cpufreq_driver->setpolicy && cpufreq_driver->get) {
+		ret_freq = cpufreq_driver->get(cpu);
+		read_unlock_irqrestore(&cpufreq_driver_lock, flags);
+		return ret_freq;
+	}
+
+	read_unlock_irqrestore(&cpufreq_driver_lock, flags);
 
 	policy = cpufreq_cpu_get(cpu);
 	if (policy) {