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

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 4c1f999041dd1fe74433d7769e18fc3cde7d7804..b4686ea6d66b295923960ff3952d4b6eb936848e 100644 (file)
--- 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);
 }