Re: [PATCH v1] s390/vfio-ap: Signal eventfd when guest AP configuration is changed

[Halil Pasic]

On Thu, 16 Jan 2025 11:52:28 -0500
Alex Williamson <alex.williamson@xxxxxxxxxx> wrote:

> > > Alex, does the above answer your question on what guards against UAF (the
> > > short answer is: matrix_dev->mdevs_lock)?    
> 
> Yes, that answers my question, thanks for untangling it.  We might
> consider a lockdep_assert_held() in the new
> signal_guest_ap_cfg_changed() since it does get called from a variety
> of paths and we need that lock to prevent the UAF.

Yes I second that! I was thinking about it myself yesterday. And there
are also a couple of other functions that expect to be called with
certain locks held. I would love to see lockdep_assert_held() there
as well.

Since I went through that code last night I could spin a patch that
catches some of these at least. But if I don't within two weeks, I
won't be grumpy if somebody else picks that up.

Regards,
Halil