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[media] media-device: better lock media_device_unregister()

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If media_device_unregister() is called by two different
drivers, a race condition may happen, as the check if the
device is not registered is not protected.

Move the spin_lock() to happen earlier in the function, in order
to prevent such race condition.

Reported-by: Shuah Khan <shuahkh@osg.samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
This commit is contained in:
Mauro Carvalho Chehab 2015-12-15 08:36:51 -02:00
parent b2ed8af910
commit 821ed36629
1 changed files with 25 additions and 11 deletions
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36
drivers/media/media-device.c
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@ -573,18 +573,13 @@ EXPORT_SYMBOL_GPL(media_device_register_entity);
* If the entity has never been registered this function will return
* immediately.
*/
void media_device_unregister_entity(struct media_entity *entity)
static void __media_device_unregister_entity(struct media_entity *entity)
{
struct media_device *mdev = entity->graph_obj.mdev;
struct media_link *link, *tmp;
struct media_interface *intf;
unsigned int i;
if (mdev == NULL)
return;
spin_lock(&mdev->lock);
/* Remove all interface links pointing to this entity */
list_for_each_entry(intf, &mdev->interfaces, graph_obj.list) {
list_for_each_entry_safe(link, tmp, &intf->links, list) {
@ -603,11 +598,23 @@ void media_device_unregister_entity(struct media_entity *entity)
/* Remove the entity */
media_gobj_destroy(&entity->graph_obj);
spin_unlock(&mdev->lock);
entity->graph_obj.mdev = NULL;
}
void media_device_unregister_entity(struct media_entity *entity)
{
struct media_device *mdev = entity->graph_obj.mdev;
if (mdev == NULL)
return;
spin_lock(&mdev->lock);
__media_device_unregister_entity(entity);
spin_unlock(&mdev->lock);
}
EXPORT_SYMBOL_GPL(media_device_unregister_entity);
/**
* media_device_register - register a media device
* @mdev: The media device
@ -666,22 +673,29 @@ void media_device_unregister(struct media_device *mdev)
struct media_entity *next;
struct media_interface *intf, *tmp_intf;
/* Check if mdev was ever registered at all */
if (!media_devnode_is_registered(&mdev->devnode))
if (mdev == NULL)
return;
spin_lock(&mdev->lock);
/* Check if mdev was ever registered at all */
if (!media_devnode_is_registered(&mdev->devnode)) {
spin_unlock(&mdev->lock);
return;
}
/* Remove all entities from the media device */
list_for_each_entry_safe(entity, next, &mdev->entities, graph_obj.list)
media_device_unregister_entity(entity);
__media_device_unregister_entity(entity);
/* Remove all interfaces from the media device */
spin_lock(&mdev->lock);
list_for_each_entry_safe(intf, tmp_intf, &mdev->interfaces,
graph_obj.list) {
__media_remove_intf_links(intf);
media_gobj_destroy(&intf->graph_obj);
kfree(intf);
}
spin_unlock(&mdev->lock);
device_remove_file(&mdev->devnode.dev, &dev_attr_model);