Re: [RFC PATCH v2 0/7] Add a root_dir option to nfs.conf

[Trond Myklebust <trondmy@hammerspace.com>]

On Tue, 2019-05-21 at 15:06 -0400, Chuck Lever wrote:
> > On May 21, 2019, at 2:17 PM, Trond Myklebust <
> > trondmy@hammerspace.com> wrote:
> > 
> > On Tue, 2019-05-21 at 13:40 -0400, Chuck Lever wrote:
> > > Hi Trond -
> > > 
> > > > On May 21, 2019, at 8:46 AM, Trond Myklebust <trondmy@gmail.com
> > > > >
> > > > wrote:
> > > > 
> > > > The following patchset adds support for the 'root_dir'
> > > > configuration
> > > > option for nfsd in nfs.conf. If a user sets this option to a
> > > > valid
> > > > directory path, then nfsd will act as if it is confined to a
> > > > chroot
> > > > jail based on that directory. All paths in /etc/exporfs and
> > > > from
> > > > exportfs are then resolved relative to that directory.
> > > 
> > > What about files under /proc that mountd might access? I assume
> > > these
> > > pathnames are not affected.
> > > 
> > That's why we have 2 threads. One thread is root jailed using
> > chroot,
> > and is used to talk to knfsd. The other thread is not root jailed
> > (or
> > at least not by root_dir) and so has full access to /etc, /proc,
> > /var,
> > ...
> > 
> > > Aren't there also one or two other files that maintain export
> > > state
> > > like /var/lib/nfs/rmtab? Are those affected?
> > 
> > See above. They are not affected.
> > 
> > > IMHO it could be less confusing to administrators to make
> > > root_dir an
> > > [exportfs] option instead of a [mountd] option, if this is not a
> > > true
> > > chroot of mountd.
> > 
> > It is neither. I made in a [nfsd] option, since it governs the way
> > that
> > both exportfs and mountd talk to nfsd.
> 
> My point is not about implementation, it's about how this
> functionality
> is presented to administrators.
> 
> In nfs.conf, [nfsd] looks like it controls what options are passed
> via
> rpc.nfsd. That still seems like a confusing admin interface.
> 
> IMO admins won't care about who is talking to whom. They will care
> about
> how the export pathnames are interpreted. That seems like it belongs
> squarely with the exportfs interface.
> 

With the exportfs interface, yes. However it is not specific to the
exportfs utility, so to me [exportfs] is more confusing than what
exists now.

OK, so what if we put it in [general] instead, and perhaps rename it
"export_rootdir"?

-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com