[PATCH v2] cpufreq: s3c: avoid use after free issue in xxx_cpufreq_reboot_notifier_evt()

[qiwuchen55@xxxxxxxxx]

From: chenqiwu <chenqiwu@xxxxxxxxxx>

There is a potential UAF issue in xxx_cpufreq_reboot_notifier_evt() that
the cpufreq policy of cpu0 has been released before using it. So we should
make a judgement to avoid it.

Signed-off-by: chenqiwu <chenqiwu@xxxxxxxxxx>
---
changes in v2:
 - use the combination of cpufreq_cpu_get() and cpufreq_cpu_put()
   instead of cpufreq_get_policy() in s3c2416-cpufreq.c
---
 drivers/cpufreq/s3c2416-cpufreq.c | 12 +++++++++++-
 drivers/cpufreq/s5pv210-cpufreq.c | 11 ++++++++++-
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/drivers/cpufreq/s3c2416-cpufreq.c b/drivers/cpufreq/s3c2416-cpufreq.c
index 1069103..f07c5d1 100644
--- a/drivers/cpufreq/s3c2416-cpufreq.c
+++ b/drivers/cpufreq/s3c2416-cpufreq.c
@@ -304,6 +304,7 @@ static int s3c2416_cpufreq_reboot_notifier_evt(struct notifier_block *this,
 {
 	struct s3c2416_data *s3c_freq = &s3c2416_cpufreq;
 	int ret;
+	struct cpufreq_policy *policy;
 
 	mutex_lock(&cpufreq_lock);
 
@@ -318,7 +319,16 @@ static int s3c2416_cpufreq_reboot_notifier_evt(struct notifier_block *this,
 	 */
 	if (s3c_freq->is_dvs) {
 		pr_debug("cpufreq: leave dvs on reboot\n");
-		ret = cpufreq_driver_target(cpufreq_cpu_get(0), FREQ_SLEEP, 0);
+
+		policy = cpufreq_cpu_get(0);
+		if (!policy) {
+			pr_debug("cpufreq: get no policy for cpu0\n");
+			return NOTIFY_BAD;
+		}
+
+		ret = cpufreq_driver_target(&policy, FREQ_SLEEP, 0);
+		cpufreq_cpu_put(policy);
+
 		if (ret < 0)
 			return NOTIFY_BAD;
 	}
diff --git a/drivers/cpufreq/s5pv210-cpufreq.c b/drivers/cpufreq/s5pv210-cpufreq.c
index 5d10030..e84281e 100644
--- a/drivers/cpufreq/s5pv210-cpufreq.c
+++ b/drivers/cpufreq/s5pv210-cpufreq.c
@@ -555,8 +555,17 @@ static int s5pv210_cpufreq_reboot_notifier_event(struct notifier_block *this,
 						 unsigned long event, void *ptr)
 {
 	int ret;
+	struct cpufreq_policy *policy;
+
+	policy = cpufreq_cpu_get(0);
+	if (!policy) {
+		pr_debug("cpufreq: get no policy for cpu0\n");
+		return NOTIFY_BAD;
+	}
+
+	ret = cpufreq_driver_target(policy, SLEEP_FREQ, 0);
+	cpufreq_cpu_put(policy);
 
-	ret = cpufreq_driver_target(cpufreq_cpu_get(0), SLEEP_FREQ, 0);
 	if (ret < 0)
 		return NOTIFY_BAD;
 
-- 
1.9.1