Re: [RFC] /dev/ioasid uAPI proposal

[Paolo Bonzini]

On 09/06/21 10:51, Enrico Weigelt, metux IT consult wrote:
> On 08.06.21 21:00, Jason Gunthorpe wrote:
>
> > Eg I can do open() on a file and I get to keep that FD. I get to keep
> > that FD even if someone later does chmod() on that file so I can't
> > open it again.
> >
> > There are lots of examples where a one time access control check
> > provides continuing access to a resource. I feel the ongoing proof is
> > the rarity in Unix.. 'revoke' is an uncommon concept in Unix..
>
> Yes, it's even possible that somebody w/ privileges opens an fd and
> hands it over to somebody unprivileged (eg. via unix socket). This is
> a very basic unix concept. If some (already opened) fd now suddenly
> behaves differently based on the current caller, that would be a break
> with traditional unix semantics.

That's already more or less meaningless for both KVM and VFIO, since 
they are tied to an mm.

Paolo