PM / devfreq: stopping the governor before device_unregister()

device_release() is freeing the resources before calling the device
specific release callback which is, in the case of devfreq, stopping
the governor.

It is a problem as some governors are using the device resources. e.g.
simpleondemand which is using the devfreq deferrable monitoring work. If it
is not stopped before the resources are freed, it might lead to a use after
free.

Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Reviewed-by: John Einar Reitan <john.reitan@arm.com>
[cw00.choi: Fix merge conflict]
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>

1 files changed, 4 insertions, 5 deletions

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index b5e7af6..1868423 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -575,10 +575,6 @@ static void devfreq_dev_release(struct device *dev)
 	list_del(&devfreq->node);
 	mutex_unlock(&devfreq_list_lock);
 
-	if (devfreq->governor)
-		devfreq->governor->event_handler(devfreq,
-						 DEVFREQ_GOV_STOP, NULL);
-
 	if (devfreq->profile->exit)
 		devfreq->profile->exit(devfreq->dev.parent);
 
@@ -714,7 +710,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
 err_init:
 	mutex_unlock(&devfreq_list_lock);
 
-	device_unregister(&devfreq->dev);
+	devfreq_remove_device(devfreq);
 	devfreq = NULL;
 err_dev:
 	if (devfreq)
@@ -735,6 +731,9 @@ int devfreq_remove_device(struct devfreq *devfreq)
 	if (!devfreq)
 		return -EINVAL;
 
+	if (devfreq->governor)
+		devfreq->governor->event_handler(devfreq,
+						 DEVFREQ_GOV_STOP, NULL);
 	device_unregister(&devfreq->dev);
 
 	return 0;