[PATCH 4.4 04/83] thermal: cpu_cooling: Avoid accessing potentially freed structures

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Viresh Kumar <viresh.ku...@linaro.org>

commit 289d72afddf83440117c35d864bf0c6309c1d011 upstream.

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.

Fixes: 02373d7c69b4 ("thermal: cpu_cooling: fix lockdep problems in 
cpu_cooling")
Signed-off-by: Viresh Kumar <viresh.ku...@linaro.org>
Reviewed-by: Lukasz Luba <lukasz.l...@arm.com>
Tested-by: Lukasz Luba <lukasz.l...@arm.com>
Signed-off-by: Eduardo Valentin <edubez...@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 drivers/thermal/cpu_cooling.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/thermal/cpu_cooling.c
+++ b/drivers/thermal/cpu_cooling.c
@@ -191,8 +191,10 @@ unsigned long cpufreq_cooling_get_level(
        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);