Re: [PATCH V2 5/7] vhost-vdpa: VHOST_IOTLB_REMAP

[Michael S. Tsirkin]

On Thu, Jul 18, 2024 at 08:45:31AM +0800, Jason Wang wrote:
> > > For example:
> > >
> > > 1) old owner pass fd to new owner which is another process
> > > 2) the new owner do VHOST_NEW_OWNER
> > > 3) new owner doesn't do remap correctly
> > >
> > > There's no way for the old owner to remove/unpin the mappings as we
> > > have the owner check in IOTLB_UPDATE. Looks like a potential way for
> > > DOS.
> >
> > This is a bug in the second cooperating process, not a DOS.  The application
> > must fix it.  Sometimes you cannot recover from an application bug at run time.
> >
> > BTW, at one time vfio enforced the concept of an owner, but Alex deleted it.
> > It adds no value, because possession of the fd is the key.
> >    ffed0518d871 ("vfio: remove useless judgement")
> 
> This seems to be a great relaxation of the ownership check. I would
> like to hear from Michael first.
> 
> Thanks

It could be that the ownership model is too restrictive.
But again, this is changing a security assumption.
Looks like yes another reason to tie this to the switch to iommufd.

-- 
MST