linux-kernel - [PATCH 3.2 092/152] regulator: core: fix race condition in regulator

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Message-ID: <lsq.1424137613.630916575@decadent.org.uk>
Date:	Tue, 17 Feb 2015 01:46:53 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Mark Brown" <broonie@...nel.org>,
	"Ashay Jaiswal" <ashayj@...eaurora.org>
Subject: [PATCH 3.2 092/152] regulator: core: fix race condition in
 regulator_put()

3.2.67-rc1 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>
[bwh: Backported to 3.2:
 - Adjust context
 - Don't touch the comment; __regulator_put() has not been split out of
   regulator_put() here]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/regulator/core.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -1314,12 +1314,14 @@ void regulator_put(struct regulator *reg
 		device_remove_file(regulator->dev, &regulator->dev_attr);
 		kfree(regulator->dev_attr.attr.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);
 	mutex_unlock(&regulator_list_mutex);

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