Re: [PATCH] kobject: make sure kobj->ktype is set before kobject_init

Kay Sievers
2007-11-29T10:59:12Z

On Thu, 2007-11-29 at 11:05 +0100, Cornelia Huck wrote:
> On Wed, 28 Nov 2007 17:00:57 -0500 (EST),
> Alan Stern <stern@rowland.harvard.edu> wrote:
> > On Wed, 28 Nov 2007, Greg KH wrote:
> > > On Wed, Nov 28, 2007 at 03:42:00PM -0500, Alan Stern wrote:
> > > > This patch (as1020) adds a check to kobject_init() to insure that the
> > > > ktype field is not NULL. This is just for safety's sake; as far as I
> > > > know there are no remaining places where the field is left unset. But
> > > > ironically, kset_init() did fail to set it! The patch fixes that and
> > > > removes some redundant initialization in kset_createa().
> > > >
> > > > The patch also fixes up elevator_init(), where ktype was set after
> > > > calling kobject_init() instead of before.
> > >
> > > No, it's safe to set ktype after kobject_init, it was just not safe to
> > > set the kset. As Kay pointed out, I just added a patch to my tree to
> > > resolve this issue, and I'll go back and update the documentation now.
> > >
> > > I do like the "check for a ktype" warning, I'll go add that to my local
> > > tree and see what breaks. Odds are, all the static kobjects will :(
> >
> > You have to be careful. The ktype check I wrote lives in
> > kobject_init() -- that's why I had to make elevator_init() assign the
> > ktype before calling kobject_init(). If you put the check into
> > kobject_add() instead then you won't end up checking objects that get
> > initialized but not added.
> >
> > Yes, nobody would deliberately use a kobject without adding it, but it
> > could happen as the result of an failure between the _init and _add
> > calls.
>
> And if someone calls kobject_put() after kobject_init() to clean up,
> their release function will not be called if they didn't set the ktype.
> So the check really belongs into kobject_init() IMO.

Hmm, will one expect that the whole object will also be free'd when we
suggest to call kobject_put() to cleanup? That might be pretty
unexpected, right?

Kay