linux-kernel - [PATCH 3.16.y-ckt 079/135] regulator: core: fix race condition in regulator

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Message-Id: <1423224113-10958-80-git-send-email-luis.henriques@canonical.com>
Date:	Fri,  6 Feb 2015 12:00:57 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Ashay Jaiswal <ashayj@...eaurora.org>,
	Mark Brown <broonie@...nel.org>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 079/135] regulator: core: fix race condition in regulator_put()

3.16.7-ckt6 -stable review patch.  If anyone has any objections, please let me know.

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

From: Ashay Jaiswal <ashayj@...eaurora.org>

commit 83b0302d347a49f951e904184afe57ac3723476e upstream.

The regulator framework maintains a list of consumer regulators
for a regulator device and protects it from concurrent access using
the regulator device's mutex lock.

In the case of regulator_put() the consumer is removed and regulator
device's parameters are updated without holding the regulator device's
mutex. This would lead to a race condition between the regulator_put()
and any function which traverses the consumer list or modifies regulator
device's parameters.
Fix this race condition by holding the regulator device's mutex in case
of regulator_put.

Signed-off-by: Ashay Jaiswal <ashayj@...eaurora.org>
Signed-off-by: Mark Brown <broonie@...nel.org>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 drivers/regulator/core.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 4c1f999041dd..b4686ea6d66b 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -1485,7 +1485,7 @@ struct regulator *regulator_get_optional(struct device *dev, const char *id)
 }
 EXPORT_SYMBOL_GPL(regulator_get_optional);
 
-/* Locks held by regulator_put() */
+/* regulator_list_mutex lock held by regulator_put() */
 static void _regulator_put(struct regulator *regulator)
 {
 	struct regulator_dev *rdev;
@@ -1500,12 +1500,14 @@ static void _regulator_put(struct regulator *regulator)
 	/* remove any sysfs entries */
 	if (regulator->dev)
 		sysfs_remove_link(&rdev->dev.kobj, regulator->supply_name);
+	mutex_lock(&rdev->mutex);
 	kfree(regulator->supply_name);
 	list_del(&regulator->list);
 	kfree(regulator);
 
 	rdev->open_count--;
 	rdev->exclusive = 0;
+	mutex_unlock(&rdev->mutex);
 
 	module_put(rdev->owner);
 }
-- 
2.1.4

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