From: "J. Bruce Fields" <bfields@fieldses.org>
To: NeilBrown <neilb@suse.com>
Cc: "Andreas Gruenbacher" <agruenba@redhat.com>,
"Miklos Szeredi" <miklos@szeredi.hu>,
"Andreas Grünbacher" <andreas.gruenbacher@gmail.com>,
"Patrick Plagwitz" <Patrick_Plagwitz@web.de>,
"linux-unionfs@vger.kernel.org" <linux-unionfs@vger.kernel.org>,
"Linux NFS list" <linux-nfs@vger.kernel.org>,
"Linux FS-devel Mailing List" <linux-fsdevel@vger.kernel.org>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] overlayfs: ignore empty NFSv4 ACLs in ext4 upperdir
Date: Fri, 3 May 2019 11:35:31 -0400 [thread overview]
Message-ID: <20190503153531.GJ12608@fieldses.org> (raw)
In-Reply-To: <87bm0l4nra.fsf@notabene.neil.brown.name>
On Thu, May 02, 2019 at 12:02:33PM +1000, NeilBrown wrote:
> On Tue, Dec 06 2016, J. Bruce Fields wrote:
>
> > On Tue, Dec 06, 2016 at 02:18:31PM +0100, Andreas Gruenbacher wrote:
> >> On Tue, Dec 6, 2016 at 11:08 AM, Miklos Szeredi <miklos@szeredi.hu> wrote:
> >> > On Tue, Dec 6, 2016 at 12:24 AM, Andreas Grünbacher
> >> > <andreas.gruenbacher@gmail.com> wrote:
> >> >> 2016-12-06 0:19 GMT+01:00 Andreas Grünbacher <andreas.gruenbacher@gmail.com>:
> >> >
> >> >>> It's not hard to come up with a heuristic that determines if a
> >> >>> system.nfs4_acl value is equivalent to a file mode, and to ignore the
> >> >>> attribute in that case. (The file mode is transmitted in its own
> >> >>> attribute already, so actually converting .) That way, overlayfs could
> >> >>> still fail copying up files that have an actual ACL. It's still an
> >> >>> ugly hack ...
> >> >>
> >> >> Actually, that kind of heuristic would make sense in the NFS client
> >> >> which could then hide the "system.nfs4_acl" attribute.
> >> >
> >> > Even simpler would be if knfsd didn't send the attribute if not
> >> > necessary. Looks like there's code actively creating the nfs4_acl on
> >> > the wire even if the filesystem had none:
> >> >
> >> > pacl = get_acl(inode, ACL_TYPE_ACCESS);
> >> > if (!pacl)
> >> > pacl = posix_acl_from_mode(inode->i_mode, GFP_KERNEL);
> >> >
> >> > What's the point?
> >>
> >> That's how the protocol is specified.
> >
> > Yep, even if we could make that change to nfsd it wouldn't help the
> > client with the large number of other servers that are out there
> > (including older knfsd's).
> >
> > --b.
> >
> >> (I'm not saying that that's very helpful.)
> >>
> >> Andreas
>
> Hi everyone.....
> I have a customer facing this problem, and so stumbled onto the email
> thread.
> Unfortunately it didn't resolve anything. Maybe I can help kick things
> along???
>
> The core problem here is that NFSv4 and ext4 use different and largely
> incompatible ACL implementations. There is no way to accurately
> translate from one to the other in general (common specific examples
> can be converted).
>
> This means that either:
> 1/ overlayfs cannot use ext4 for upper and NFS for lower (or vice
> versa) or
> 2/ overlayfs need to accept that sometimes it cannot copy ACLs, and
> that is OK.
>
> Silently not copying the ACLs is probably not a good idea as it might
> result in inappropriate permissions being given away. So if the
> sysadmin wants this (and some clearly do), they need a way to
> explicitly say "I accept the risk".
So, I feel like silently copying ACLs up *also* carries a risk, if that
means switching from server-enforcement to client-enforcement of those
permissions.
Sorry, I know we had another thread recently about permissions in this
situation, and I've forgotten the conclusion.
Out of curiosity, what's done with selinux labels?
--b.
> If only standard Unix permissions
> are used, there is no risk, so this seems reasonable.
>
> So I would like to propose a new option for overlayfs
> nocopyupacl: when overlayfs is copying a file (or directory etc)
> from the lower filesystem to the upper filesystem, it does not
> copy extended attributes with the "system." prefix. These are
> used for storing ACL information and this is sometimes not
> compatible between different filesystem types (e.g. ext4 and
> NFSv4). Standard Unix ownership permission flags (rwx) *are*
> copied so this option does not risk giving away inappropriate
> permissions unless the lowerfs uses unusual ACLs.
>
>
> Miklos: would you find that acceptable?
>
> Thanks,
> NeilBrown
>
>
next prev parent reply other threads:[~2019-05-03 15:35 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <5a6862bd-924d-25e4-2a8e-ba4f51e66604@web.de>
2016-12-05 9:28 ` [PATCH] overlayfs: ignore empty NFSv4 ACLs in ext4 upperdir Miklos Szeredi
2016-12-05 15:19 ` J. Bruce Fields
2016-12-05 15:36 ` Miklos Szeredi
2016-12-05 16:25 ` J. Bruce Fields
2016-12-05 18:25 ` Patrick Plagwitz
2016-12-05 19:37 ` Andreas Grünbacher
2016-12-05 22:58 ` Patrick Plagwitz
2016-12-05 23:19 ` Andreas Grünbacher
2016-12-05 23:24 ` Andreas Grünbacher
2016-12-06 10:08 ` Miklos Szeredi
2016-12-06 13:18 ` Andreas Gruenbacher
2016-12-06 18:58 ` J. Bruce Fields
2019-05-02 2:02 ` NeilBrown
2019-05-02 2:54 ` Amir Goldstein
2019-05-02 3:57 ` NeilBrown
2019-05-02 14:04 ` Andreas Gruenbacher
2019-05-02 14:28 ` Miklos Szeredi
2019-05-02 15:08 ` Andreas Grünbacher
2019-05-02 17:16 ` J. Bruce Fields
2019-05-02 17:53 ` Andreas Gruenbacher
2019-05-02 23:04 ` NeilBrown
2019-05-02 23:24 ` NeilBrown
2019-05-03 6:54 ` Andreas Grünbacher
2019-05-02 17:26 ` Goetz, Patrick G
2019-05-02 17:44 ` Andreas Gruenbacher
2019-05-02 17:51 ` Goetz, Patrick G
2019-05-03 15:27 ` J. Bruce Fields
2019-05-03 17:39 ` Goetz, Patrick G
2019-05-02 4:35 ` [PATCH] OVL: add honoracl=off mount option NeilBrown
2019-05-02 5:08 ` Randy Dunlap
2019-05-02 11:46 ` Amir Goldstein
2019-05-02 23:19 ` NeilBrown
2019-05-02 13:47 ` J. R. Okajima
2019-05-03 15:35 ` J. Bruce Fields [this message]
2019-05-03 17:26 ` [PATCH] overlayfs: ignore empty NFSv4 ACLs in ext4 upperdir Amir Goldstein
2019-05-03 17:31 ` J. Bruce Fields
2019-05-03 17:41 ` Amir Goldstein
2019-05-03 17:51 ` Vivek Goyal
2019-05-07 0:24 ` NeilBrown
2019-05-10 20:09 ` J. Bruce Fields
2019-09-18 9:07 ` Miklos Szeredi
2019-09-18 19:49 ` J. Bruce Fields
2019-05-07 8:07 ` Miklos Szeredi
2019-05-07 23:51 ` J. Bruce Fields
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