From: "Andreas Grünbacher" <andreas.gruenbacher@gmail.com>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: Andreas Gruenbacher <agruenba@redhat.com>,
NeilBrown <neilb@suse.com>, Amir Goldstein <amir73il@gmail.com>,
"J. Bruce Fields" <bfields@fieldses.org>,
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: Thu, 2 May 2019 17:08:14 +0200 [thread overview]
Message-ID: <CAHpGcML0KuoGSyXyyDnXHkSp3nDnSjJPeZeWEmt8CXxQeojxwg@mail.gmail.com> (raw)
In-Reply-To: <CAJfpegsthQn_=3AQJf7ojxoQBpHMA3dz1fCBjNZXsCA1E0oqnw@mail.gmail.com>
Am Do., 2. Mai 2019 um 16:28 Uhr schrieb Miklos Szeredi <miklos@szeredi.hu>:
> On Thu, May 2, 2019 at 10:05 AM Andreas Gruenbacher <agruenba@redhat.com> wrote:
> > On Thu, 2 May 2019 at 05:57, NeilBrown <neilb@suse.com> wrote:
> > > On Wed, May 01 2019, Amir Goldstein wrote:
> > > > On Wed, May 1, 2019 at 10:03 PM NeilBrown <neilb@suse.com> 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.
> >
> > I still think the nfs client could make this problem mostly go away by
> > not exposing "system.nfs4_acl" xattrs when the acl is equivalent to
> > the file mode. The richacl patches contain a workable abgorithm for
> > that. The problem would remain for files that have an actual NFS4 ACL,
> > which just cannot be mapped to a file mode or to POSIX ACLs in the
> > general case, as well as for files that have a POSIX ACL. Mapping NFS4
> > ACL that used to be a POSIX ACL back to POSIX ACLs could be achieved
> > in many cases as well, but the code would be quite messy. A better way
> > seems to be to using a filesystem that doesn't support POSIX ACLs in
> > the first place. Unfortunately, xfs doesn't allow turning off POSIX
> > ACLs, for example.
>
> How about mounting NFSv4 with noacl? That should fix this issue, right?
You'll still see permissions that differ from what the filesystem
enforces, and copy-up would change that behavior.
Andreas
> Thanks,
> Miklos
>
>
>
> >
> > Andreas
> >
> > > >> >> > 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.
> > > >
> > > > For example? permissions given away to do what?
> > > > Note that ovl_permission() only check permissions of *mounter*
> > > > to read the lower NFS file and ovl_open()/ovl_read_iter() access
> > > > the lower file with *mounter* credentials.
> > > >
> > > > I might be wrong, but seems to me that once admin mounted
> > > > overlayfs with lower NFS, NFS ACLs are not being enforced at all
> > > > even before copy up.
> > >
> > > I guess it is just as well that copy-up fails then - if the lower-level
> > > permission check is being ignored.
> > >
> > > >
> > > >> So if the
> > > >> sysadmin wants this (and some clearly do), they need a way to
> > > >> explicitly say "I accept the risk". 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.
> > > >>
> > > >>
> > > >
> > > > I am wondering if it would make more sense for nfs to register a
> > > > security_inode_copy_up_xattr() hook.
> > > > That is the mechanism that prevents copying up other security.*
> > > > xattrs?
> > >
> > > No, I don't think that would make sense.
> > > Support some day support for nfs4 acls were added to ext4 (not a totally
> > > ridiculous suggestion). We would then want NFS to allow it's ACLs to be
> > > copied up.
> > >
> > > Thanks,
> > > NeilBrown
> > >
> > >
> > > >
> > > > Thanks,
> > > > Amir.
next prev parent reply other threads:[~2019-05-02 15:08 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 [this message]
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 ` [PATCH] overlayfs: ignore empty NFSv4 ACLs in ext4 upperdir J. Bruce Fields
2019-05-03 17:26 ` 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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAHpGcML0KuoGSyXyyDnXHkSp3nDnSjJPeZeWEmt8CXxQeojxwg@mail.gmail.com \
--to=andreas.gruenbacher@gmail.com \
--cc=Patrick_Plagwitz@web.de \
--cc=agruenba@redhat.com \
--cc=amir73il@gmail.com \
--cc=bfields@fieldses.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-nfs@vger.kernel.org \
--cc=linux-unionfs@vger.kernel.org \
--cc=miklos@szeredi.hu \
--cc=neilb@suse.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).