Re: [RFC] /dev/ioasid uAPI proposal

[Jason Gunthorpe]

On Wed, Jun 09, 2021 at 11:11:17AM +0200, Paolo Bonzini wrote:
> 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.

vfio isn't supposed to be tied to a mm.

Jason