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[media] v4l: Don't access media entity after is has been destroyed 

Entities associated with video device nodes are unregistered in
video_unregister_device(). This destroys the entity even though it can
still be accessed through open video device nodes.

Move the media_device_unregister_entity() call from
video_unregister_device() to v4l2_device_release() to ensure that the
entity isn't unregistered until the last reference to the video device
is released.

Also remove the media_entity_get()/put() calls from v4l2-dev.c. Those
functions were designed for subdevs, to avoid a parent module from being
removed while still accessible through board code. They're not currently
needed for video device nodes, and will oops when a hotpluggable device
is disconnected during streaming, as media_entity_put() called in
v4l2_device_release() tries to access entity->parent->dev->driver which
is set to NULL when the device is disconnected.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Sakari Ailus <sakari.ailus@iki.fi>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
This commit is contained in:
Laurent Pinchart 2011-06-15 05:20:34 -03:00 committed by Mauro Carvalho Chehab
parent ca4186f06f
commit c064b8eac8
1 changed files with 7 additions and 32 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

39
drivers/media/video/v4l2-dev.c
View File

@ -167,6 +167,12 @@ static void v4l2_device_release(struct device *cd)
mutex_unlock(&videodev_lock);
#if defined(CONFIG_MEDIA_CONTROLLER)
if (vdev->v4l2_dev && vdev->v4l2_dev->mdev &&
vdev->vfl_type != VFL_TYPE_SUBDEV)
media_device_unregister_entity(&vdev->entity);
#endif
/* Release video_device and perform other
cleanups as needed. */
vdev->release(vdev);
@ -389,9 +395,6 @@ static int v4l2_mmap(struct file *filp, struct vm_area_struct *vm)
static int v4l2_open(struct inode *inode, struct file *filp)
{
struct video_device *vdev;
#if defined(CONFIG_MEDIA_CONTROLLER)
struct media_entity *entity = NULL;
#endif
int ret = 0;
/* Check if the video device is available */
@ -405,17 +408,6 @@ static int v4l2_open(struct inode *inode, struct file *filp)
/* and increase the device refcount */
video_get(vdev);
mutex_unlock(&videodev_lock);
#if defined(CONFIG_MEDIA_CONTROLLER)
if (vdev->v4l2_dev && vdev->v4l2_dev->mdev &&
vdev->vfl_type != VFL_TYPE_SUBDEV) {
entity = media_entity_get(&vdev->entity);
if (!entity) {
ret = -EBUSY;
video_put(vdev);
return ret;
}
}
#endif
if (vdev->fops->open) {
if (vdev->lock && mutex_lock_interruptible(vdev->lock)) {
ret = -ERESTARTSYS;
@ -431,14 +423,8 @@ static int v4l2_open(struct inode *inode, struct file *filp)
err:
/* decrease the refcount in case of an error */
if (ret) {
#if defined(CONFIG_MEDIA_CONTROLLER)
if (vdev->v4l2_dev && vdev->v4l2_dev->mdev &&
vdev->vfl_type != VFL_TYPE_SUBDEV)
media_entity_put(entity);
#endif
if (ret)
video_put(vdev);
}
return ret;
}
@ -455,11 +441,6 @@ static int v4l2_release(struct inode *inode, struct file *filp)
if (vdev->lock)
mutex_unlock(vdev->lock);
}
#if defined(CONFIG_MEDIA_CONTROLLER)
if (vdev->v4l2_dev && vdev->v4l2_dev->mdev &&
vdev->vfl_type != VFL_TYPE_SUBDEV)
media_entity_put(&vdev->entity);
#endif
/* decrease the refcount unconditionally since the release()
return value is ignored. */
video_put(vdev);
@ -754,12 +735,6 @@ void video_unregister_device(struct video_device *vdev)
if (!vdev || !video_is_registered(vdev))
return;
#if defined(CONFIG_MEDIA_CONTROLLER)
if (vdev->v4l2_dev && vdev->v4l2_dev->mdev &&
vdev->vfl_type != VFL_TYPE_SUBDEV)
media_device_unregister_entity(&vdev->entity);
#endif
mutex_lock(&videodev_lock);
/* This must be in a critical section to prevent a race with v4l2_open.
* Once this bit has been cleared video_get may never be called again.