Re: [PATCH v2 3/6] landlock: Bump ABI for LANDLOCK_SCOPE_SYSV_MSG_QUEUE

On Fri, Aug 21, 2026 at 09:15:31AM -0400, Justin Suess wrote:
> On Fri, Aug 21, 2026 at 02:38:15PM +0200, Günther Noack wrote:
> > On Mon, Jul 27, 2026 at 07:08:30PM -0400, Justin Suess wrote:
> > > Bump the ABI version for Landlock SysV message queue scoping.
> > > 
> > > Signed-off-by: Justin Suess <[email protected]>
> > 
> > The ABI bump is normally put into the same commit as the
> > implementation for easier backporting. Otherwise, looks good.
> I'll squash them.
> 
> >
> Thanks,
> 
> I did wonder about if we need to use the landlock_object here?
> 
> I'm pretty sure SysV message queues stay open after process exit,
> which could cause the domain to be pinned by landlock_cred_security,
> if programs are lazy and don't close them.
> 
> So it probably needs to be a weak reference. 
> 
> But it's unclear what should be the behavior there when the domain
> is dropped:
> 
> 1. Should it become inaccessible and belong to *nobody's* domain?
> 
> (i.e when owning domain is dropped, the queue belongs to no domain and is inaccessible to
> all LANDLOCK_SCOPE_SYSV_MSG_QUEUE scoped domains)
> 
> 2. Should it be moved to the parent's domain?
> 
> (i.e when owning domain is dropped, the parent domain is the new scope,
> and then it's parent, so on and so forth, more complicated, but more correct)
> 
> 3. Or be kept as is.
> 
> (i.e Allow an open sysv message queue to pin a domain
> for it's lifetime)
>
Scratch all of this, I think it's best if the kern_ipc_blob takes a reference to
the landlock_hierarchy plus a depth u16.

I think this will require introducing a new
landlock_put_hierarchy_deferred method because of the runtime context of
the ipc hooks, but should be pretty easy.

Also refactor domain_is_scoped() to take the server side as (hierarchy, depth).

Justin
> Either way this almost certainly needs to be rebased since it's been
> a little bit and there were significant refactorings of the domain and
> ruleset structures since the tracepoints series.
> 
> Justin
> 
> > –Günther