[media] media-entity: cache media_device on object removal
As pointed by Dan, the commit f8fd4c61b5ae ("[media] media-entity:
protect object creation/removal using spin lock")' leads to the
following static checker warning:
drivers/media/media-entity.c:781 media_remove_intf_link()
error: dereferencing freed memory 'link'
drivers/media/media-entity.c
777 void media_remove_intf_link(struct media_link *link)
778 {
779 spin_lock(&link->graph_obj.mdev->lock);
780 __media_remove_intf_link(link);
781 spin_unlock(&link->graph_obj.mdev->lock);
In practice, I didn't see any troubles even with KASAN enabled. I guess
gcc optimizer internally cached the mdev reference, instead of getting
it twice. Yet, it is a very bad idea to rely on such optimization. So,
let's fix the code.
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
diff --git a/drivers/media/media-entity.c b/drivers/media/media-entity.c
index f88740b..13c8ca1 100644
--- a/drivers/media/media-entity.c
+++ b/drivers/media/media-entity.c
@@ -580,13 +580,15 @@
void media_entity_remove_links(struct media_entity *entity)
{
+ struct media_device *mdev = entity->graph_obj.mdev;
+
/* Do nothing if the entity is not registered. */
- if (entity->graph_obj.mdev == NULL)
+ if (mdev == NULL)
return;
- spin_lock(&entity->graph_obj.mdev->lock);
+ spin_lock(&mdev->lock);
__media_entity_remove_links(entity);
- spin_unlock(&entity->graph_obj.mdev->lock);
+ spin_unlock(&mdev->lock);
}
EXPORT_SYMBOL_GPL(media_entity_remove_links);
@@ -781,9 +783,15 @@
void media_remove_intf_link(struct media_link *link)
{
- spin_lock(&link->graph_obj.mdev->lock);
+ struct media_device *mdev = link->graph_obj.mdev;
+
+ /* Do nothing if the intf is not registered. */
+ if (mdev == NULL)
+ return;
+
+ spin_lock(&mdev->lock);
__media_remove_intf_link(link);
- spin_unlock(&link->graph_obj.mdev->lock);
+ spin_unlock(&mdev->lock);
}
EXPORT_SYMBOL_GPL(media_remove_intf_link);
@@ -799,12 +807,14 @@
void media_remove_intf_links(struct media_interface *intf)
{
+ struct media_device *mdev = intf->graph_obj.mdev;
+
/* Do nothing if the intf is not registered. */
- if (intf->graph_obj.mdev == NULL)
+ if (mdev == NULL)
return;
- spin_lock(&intf->graph_obj.mdev->lock);
+ spin_lock(&mdev->lock);
__media_remove_intf_links(intf);
- spin_unlock(&intf->graph_obj.mdev->lock);
+ spin_unlock(&mdev->lock);
}
EXPORT_SYMBOL_GPL(media_remove_intf_links);