regulator: core: fix race condition in regulator_put()

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>
Cc: stable@vger.kernel.org

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index e225711..9c48fb3 100644 (file)
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -1488,7 +1488,7 @@ struct regulator *regulator_get_optional(struct device *dev, const char *id)
 }
 EXPORT_SYMBOL_GPL(regulator_get_optional);
 
 }
 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;
 static void _regulator_put(struct regulator *regulator)
 {
        struct regulator_dev *rdev;


@@ -1503,12 +1503,14 @@ static void _regulator_put(struct regulator *regulator)
        /* remove any sysfs entries */
        if (regulator->dev)
                sysfs_remove_link(&rdev->dev.kobj, regulator->supply_name);
        /* 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;
        kfree(regulator->supply_name);
        list_del(&regulator->list);
        kfree(regulator);
 
        rdev->open_count--;
        rdev->exclusive = 0;

+       mutex_unlock(&rdev->mutex);

 
        module_put(rdev->owner);
 }
 
        module_put(rdev->owner);
 }