linux-kernel - [PATCH 1/2] devfreq: fix use after free in devfreq_remove

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Date:	Thu, 10 Nov 2011 15:28:11 +0800
From:	Axel Lin <axel.lin@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	MyungJoo Ham <myungjoo.ham@...sung.com>,
	Kevin Hilman <khilman@...com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Mike Turquette <mturquette@...com>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: [PATCH 1/2] devfreq: fix use after free in devfreq_remove_device

In devfreq_remove_device, calling _remove_devfreq will also free devfreq.
Don't dereference devfreq->governor->no_central_polling after _remove_devfreq.

Signed-off-by: Axel Lin <axel.lin@...il.com>
---
 drivers/devfreq/devfreq.c |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index d065925..59d24e9 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -418,10 +418,14 @@ out:
  */
 int devfreq_remove_device(struct devfreq *devfreq)
 {
+	bool central_polling;
+
 	if (!devfreq)
 		return -EINVAL;
 
-	if (!devfreq->governor->no_central_polling) {
+	central_polling = !devfreq->governor->no_central_polling;
+
+	if (central_polling) {
 		mutex_lock(&devfreq_list_lock);
 		while (wait_remove_device == devfreq) {
 			mutex_unlock(&devfreq_list_lock);
@@ -433,7 +437,7 @@ int devfreq_remove_device(struct devfreq *devfreq)
 	mutex_lock(&devfreq->lock);
 	_remove_devfreq(devfreq, false); /* it unlocks devfreq->lock */
 
-	if (!devfreq->governor->no_central_polling)
+	if (central_polling)
 		mutex_unlock(&devfreq_list_lock);
 
 	return 0;
-- 
1.7.5.4



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