thermal: cpu_cooling: Avoid accessing potentially freed structures

After the lock is dropped, it is possible that the cpufreq_dev gets
freed before we call get_level() and that can cause kernel to crash.

Drop the lock after we are done using the structure.

Cc: 4.2+ <stable@vger.kernel.org> # 4.2+
Fixes: 02373d7c69b4 ("thermal: cpu_cooling: fix lockdep problems in cpu_cooling")
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Tested-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c
index 69d0f430b2d190756de94d4b6b6334d1af2dfa50..be29489dd247508dcc8d66df79cc21a0d669ad3c 100644 (file)
--- a/drivers/thermal/cpu_cooling.c
+++ b/drivers/thermal/cpu_cooling.c
@@ -153,8 +153,10 @@ unsigned long cpufreq_cooling_get_level(unsigned int cpu, unsigned int freq)
        mutex_lock(&cooling_list_lock);
        list_for_each_entry(cpufreq_dev, &cpufreq_dev_list, node) {
                if (cpumask_test_cpu(cpu, &cpufreq_dev->allowed_cpus)) {
+                       unsigned long level = get_level(cpufreq_dev, freq);
+
                        mutex_unlock(&cooling_list_lock);
-                       return get_level(cpufreq_dev, freq);
+                       return level;
                }
        }
        mutex_unlock(&cooling_list_lock);