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[media] media-entity: cache media_device on object removal

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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>
This commit is contained in:
Mauro Carvalho Chehab 2015-12-15 08:01:13 -02:00
parent 5c883edb5b
commit cc4a82581c
1 changed files with 18 additions and 8 deletions
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26
drivers/media/media-entity.c
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@ -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);