Commit c75361c0 authored Mar 11, 2016 by Richard Cochran Committed by Rafael J. Wysocki Mar 18, 2016

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>

parent 4fec7ad5

drivers/cpufreq/cpufreq.c

+10 −2

Original line number	Diff line number	Diff line
		@@ -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) {

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