regulator: core: fix race condition in regulator_put()

commit 83b0302d 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>
[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@decadent.org.uk>

drivers/regulator/core.c

@@ -1314,12 +1314,14 @@ void regulator_put(struct regulator *regulator)
 		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);