[3.16.y-ckt stable] Patch "regulator: core: fix race condition in regulator_put()" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    regulator: core: fix race condition in regulator_put()

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt6.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 032d538aea9001af8703bfdd56eea2de94c920ff Mon Sep 17 00:00:00 2001
From: Ashay Jaiswal <ashayj at codeaurora.org>
Date: Thu, 8 Jan 2015 18:54:25 +0530
Subject: regulator: core: fix race condition in regulator_put()

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 at codeaurora.org>
Signed-off-by: Mark Brown <broonie at kernel.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.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