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
