linux-kernel - [PATCH] PM / devfreq: missing rcu_read_lock() added for find_device

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Message-id: <1353492634-10730-1-git-send-email-myungjoo.ham@samsung.com>
Date:	Wed, 21 Nov 2012 19:10:34 +0900
From:	MyungJoo Ham <myungjoo.ham@...sung.com>
To:	linux-pm@...r.kernel.org
Cc:	rjw@...k.pl, keescook@...omium.org, serge.hallyn@...onical.com,
	linux-kernel@...r.kernel.org, myungjoo.ham@...il.com
Subject: [PATCH] PM / devfreq: missing rcu_read_lock() added for
 find_device_opp()

opp_get_notifier() uses find_device_opp(), which requires to
held rcu_read_lock. In order to keep the notifier-header
valid, we have added rcu_read_lock().

Reported-by: Kees Cook <keescook@...omium.org>
Signed-off-by: MyungJoo Ham <myungjoo.ham@...sung.com>
---
 drivers/devfreq/devfreq.c |   26 ++++++++++++++++++++------
 1 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 45e053e..e91cb22 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -1023,11 +1023,18 @@ struct opp *devfreq_recommended_opp(struct device *dev, unsigned long *freq,
  */
 int devfreq_register_opp_notifier(struct device *dev, struct devfreq *devfreq)
 {
-	struct srcu_notifier_head *nh = opp_get_notifier(dev);
+	struct srcu_notifier_head *nh;
+	int ret = 0;
 
+	rcu_read_lock();
+	nh = opp_get_notifier(dev);
 	if (IS_ERR(nh))
-		return PTR_ERR(nh);
-	return srcu_notifier_chain_register(nh, &devfreq->nb);
+		ret = PTR_ERR(nh);
+	if (!ret)
+		ret = srcu_notifier_chain_register(nh, &devfreq->nb);
+	rcu_read_unlock();
+
+	return ret;
 }
 
 /**
@@ -1042,11 +1049,18 @@ int devfreq_register_opp_notifier(struct device *dev, struct devfreq *devfreq)
  */
 int devfreq_unregister_opp_notifier(struct device *dev, struct devfreq *devfreq)
 {
-	struct srcu_notifier_head *nh = opp_get_notifier(dev);
+	struct srcu_notifier_head *nh;
+	int ret = 0;
 
+	rcu_read_lock();
+	nh = opp_get_notifier(dev);
 	if (IS_ERR(nh))
-		return PTR_ERR(nh);
-	return srcu_notifier_chain_unregister(nh, &devfreq->nb);
+		ret = PTR_ERR(nh);
+	if (!ret)
+		ret = srcu_notifier_chain_unregister(nh, &devfreq->nb);
+	rcu_read_unlock();
+
+	return ret;
 }
 
 MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@...sung.com>");
-- 
1.7.5.4

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