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Subject: Re: [RFC PATCH v2 0/7] Add a root_dir option to nfs.conf
From:   Chuck Lever <chuck.lever@oracle.com>
In-Reply-To: <501262c68530acbce21f39e0015e76805dedfe48.camel@hammerspace.com>
Date:   Tue, 28 May 2019 11:30:07 -0400
Cc:     Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
        Steve Dickson <SteveD@redhat.com>
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References: <20190521124701.61849-1-trond.myklebust@hammerspace.com>
 <708D03B6-AEE1-42D6-ABDF-FB1AA5FC9A94@gmail.com>
 <25ce1d3aa852ecd09ff300233aea60b71e6e69df.camel@hammerspace.com>
 <1BB55244-E893-47A2-B4CB-36CA991A84B0@gmail.com>
 <501262c68530acbce21f39e0015e76805dedfe48.camel@hammerspace.com>
To:     Trond Myklebust <trondmy@hammerspace.com>
Sender: linux-nfs-owner@vger.kernel.org
Precedence: bulk


> On May 21, 2019, at 3:58 PM, Trond Myklebust <trondmy@hammerspace.com> =
wrote:
>=20
> 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:
>>>=20
>>> On Tue, 2019-05-21 at 13:40 -0400, Chuck Lever wrote:
>>>> Hi Trond -
>>>>=20
>>>>> On May 21, 2019, at 8:46 AM, Trond Myklebust <trondmy@gmail.com
>>>>>>=20
>>>>> wrote:
>>>>>=20
>>>>> 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.
>>>>=20
>>>> What about files under /proc that mountd might access? I assume
>>>> these
>>>> pathnames are not affected.
>>>>=20
>>> 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,
>>> ...
>>>=20
>>>> Aren't there also one or two other files that maintain export
>>>> state
>>>> like /var/lib/nfs/rmtab? Are those affected?
>>>=20
>>> See above. They are not affected.
>>>=20
>>>> 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.
>>>=20
>>> It is neither. I made in a [nfsd] option, since it governs the way
>>> that
>>> both exportfs and mountd talk to nfsd.
>>=20
>> My point is not about implementation, it's about how this
>> functionality
>> is presented to administrators.
>>=20
>> In nfs.conf, [nfsd] looks like it controls what options are passed
>> via
>> rpc.nfsd. That still seems like a confusing admin interface.
>>=20
>> 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.
>>=20
>=20
> 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.
>=20
> OK, so what if we put it in [general] instead, and perhaps rename it
> "export_rootdir"?

For the record, I prefer export_rootdir to root_dir. I haven't
thought of a better choice.

I also like not putting this option under [nfsd]. [general] is
a better choice IMO, though I'm still not crazy about it.

It might be nice to have a new section called "[exports]" (no "f").


--
Chuck Lever