Re: [PATCH] overlayfs: ignore empty NFSv4 ACLs in ext4 upperdir

From: J. Bruce Fields
Date: Fri May 10 2019 - 16:11:08 EST

On Tue, May 07, 2019 at 10:24:58AM +1000, NeilBrown wrote:
> Interesting perspective .... though doesn't NFSv4 explicitly allow
> client-side ACL enforcement in the case of delegations?

Not really. What you're probably thinking of is the single ACE that the
server can return on granting a delegation, that tells the client it can
skip the ACCESS check for users matching that ACE. It's unclear how
useful that is. It's currently unused by the Linux client and server.

> Not sure how relevant that is....
> It seems to me we have two options:
> 1/ declare the NFSv4 doesn't work as a lower layer for overlayfs and
> recommend people use NFSv3, or
> 2/ Modify overlayfs to work with NFSv4 by ignoring nfsv4 ACLs either
> 2a/ always - and ignore all other acls and probably all system. xattrs,
> or
> 2b/ based on a mount option that might be
> 2bi/ general "noacl" or might be
> 2bii/ explicit "noxattr=system.nfs4acl"
> I think that continuing to discuss the miniature of the options isn't
> going to help. No solution is perfect - we just need to clearly
> document the implications of whatever we come up with.
> I lean towards 2a, but I be happy with with any '2' and '1' won't kill
> me.

I guess I'd also lean towards 2a.

I don't think it applies to posix acls, as overlayfs is capable of
copying those up and evaluating them on its own.


> Do we have a vote? Or does someone make an executive decision??
> NeilBrown