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Commit cc4a8258 authored by Mauro Carvalho Chehab's avatar Mauro Carvalho Chehab
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[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: default avatarDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@osg.samsung.com>
parent 5c883edb

drivers/media/media-entity.c

+18 −8
Original line number Diff line number Diff line
@@ -580,13 +580,15 @@ EXPORT_SYMBOL_GPL(__media_entity_remove_links); 


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 @@ EXPORT_SYMBOL_GPL(__media_remove_intf_link); 


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 @@ EXPORT_SYMBOL_GPL(__media_remove_intf_links); 


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);