Messages in this thread | | | Subject | Re: [PATCH] [media] media-entity: only call dev_dbg_obj if mdev is not NULL | From | Helen Koike <> | Date | Fri, 7 Apr 2017 11:36:29 -0300 |
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Hi Sakari,
On 2017-04-07 04:40 AM, Sakari Ailus wrote: > Hi Helen, > > On Thu, Apr 06, 2017 at 04:32:00PM -0300, Helen Koike wrote: >> Fix kernel Oops NULL pointer deference >> Call dev_dbg_obj only after checking if gobj->mdev is not NULL >> >> Signed-off-by: Helen Koike <helen.koike@collabora.com> >> --- >> drivers/media/media-entity.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/media/media-entity.c b/drivers/media/media-entity.c >> index 5640ca2..bc44193 100644 >> --- a/drivers/media/media-entity.c >> +++ b/drivers/media/media-entity.c >> @@ -199,12 +199,12 @@ void media_gobj_create(struct media_device *mdev, >> >> void media_gobj_destroy(struct media_gobj *gobj) >> { >> - dev_dbg_obj(__func__, gobj); >> - >> /* Do nothing if the object is not linked. */ >> if (gobj->mdev == NULL) >> return; >> >> + dev_dbg_obj(__func__, gobj); >> + >> gobj->mdev->topology_version++; >> >> /* Remove the object from mdev list */ > > Where is media_gobj_destroy() called with an object with NULL mdev? > > I do not object to the change, but would like to know because I don't think > it's supposed to happen.
This happens when media_device_unregister(mdev) is called before unregistering the subdevices v4l2_device_unregister_subdev(sd) (which should be possible).
v4l2_device_unregister_subdev(sd) ends up calling v4l2_device_release() that calls media_device_unregister_entity() again (previously called by media_device_unregister(mdev)
Helen
> > There are issues though, until the patches fixing object referencing are > finished and merged. Unfortunately I haven't been able to work on those > recently, will pick them up again soon... >
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