[PATCH] LP #220658 stat broken for CIFS filesystem

[Jim Lieb]

On Wednesday 07 January 2009 10:07:10 Steve Langasek wrote:
> On Wed, Jan 07, 2009 at 08:35:19AM -0700, Tim Gardner wrote:
> > Jim Lieb wrote:
> > > This is a regression from 7.10 and other linux CIFS clients.
> > >
> > > This patch enables CONFIG_CIFS_XATTR and CONFIG_CIFS_POSIX to
> > > change the protocol options to request Posix functionality.
> > > 7.10 and other Linux distros such as Fedora enable these options in
> > > order to allow full UNIX f/s functionality between Linux
> > > client/server(s).  See the commit comments for the details.
> > >
> > > This patch applies to Intrepid.
> > >
> > > Proposing for SRU to Intrepid and Jaunty.
> >
> > ACK - though I suspect Stefan would prefer to wait until the current
> > Intrepid kernel is promoted to -updates. Furthermore, I don't think its
> > fair to say that this is a regression from 7.10. As far as I can tell,
> > no Ubuntu release (7.10 or otherwise) has enabled CIFS_XATTR.
> >
> > You'll want to engage at least Steve Langasek as he seems to be quite
> > interested in Samba issues.
>
> Hmm, TTBOMK the CIFS_XATTR option is new functionality in the cifs driver
> that postdates Ubuntu 7.10.  It may be a regression in the sense that 7.10
> still supported smbfs and smbfs may have implemented this, but that's not a
> direct regression in the cifs driver itself.
>
> I am wary of changing these options in an SRU though, because I have seen
> reports from Debian kernels of roughly the same vintage that there's no way
> on the client side to down-negotiate to not use POSIX passthrough
> semantics, which is sometimes what's called for.  Basically, enabling these
> options could represent a security-related regression for users who are
> already happily using the current settings.
How is this a security related issue?  Posix semantics mean case sensitivity 
and attributes (if used), something that UNIX/Linux programs expect.  Are 
there use cases we can enumerate where security is an issue?  These need
to be well documented if we are to be at variance with other enterprise 
distros.
-- 
Jim Lieb
Ubuntu Kernel Team
Canonical Ltd.