Re: [Lsf-pc] [LSF/MM ATTEND] Richacls

[Jeremy Allison <jra@samba.org>]

On Tue, Jan 13, 2015 at 12:40:29PM -0500, J. Bruce Fields wrote:
> On Tue, Jan 13, 2015 at 06:23:26PM +0100, Andreas Gruenbacher wrote:
> > On 01/13/2015 05:48 PM, Jeremy Allison wrote:
> > >My understanding of Christoph's objection (although I'm sure
> > >he can chime in himself :-) was that he wanted to see POSIX
> > >ACLs reworked as a mapping on top of RichACLs, so that ultimately
> > >RichACLs would be the only on-disk format of the EA.
> > >
> > >I think that is doable, as I think any POSIX ACL can be represented
> > >as an underlying RichACL, just not the reverse.
> > 
> > On of the differences is that permissions in POSIX ACLs do
> > accumulate, while in NFSv4 and CIFS ACLs, and therefore also
> > richacls, they do not. So the two models are really not
> > interchangeable, however annoying that may be.
> > 
> > For example, with the following POSIX ACL, a non-root process in
> > group 5001 and 5002 would not be allowed to open f with O_RDWR, only
> > with O_RDONLY *or* O_WRONLY.
> > 
> >   # file: f
> >   # owner: root
> >   # group: root
> >   user::rw-
> >   group::rw-
> >   group:5001:r--
> >   group:5002:-w-
> >   mask::rw-
> >   other::---
> > 
> > In all the other ACL models, the process would be allowed to open f
> > with O_RDWR.
> 
> If we modified the behavior to permit O_RDWR in this case, would that
> cause anyone a problem?

Hmmmm. It changes userspace visible behavior. I can't think of any reason
anyone would be relying on this (other than bugs :-) but still...