From: NeilBrown <neilb@suse.com>
To: Amir Goldstein <amir73il@gmail.com>
Cc: "J. Bruce Fields" <bfields@fieldses.org>,
"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: Thu, 02 May 2019 13:57:03 +1000 [thread overview]
Message-ID: <875zqt4igg.fsf@notabene.neil.brown.name> (raw)
In-Reply-To: <CAOQ4uxjYEjqbLcVYoUaPzp-jqY_3tpPBhO7cE7kbq63XrPRQLQ@mail.gmail.com>
[-- Attachment #1: Type: text/plain, Size: 4469 bytes --]
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.
>> >> >
>> >> > 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.
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 832 bytes --]
next prev parent reply other threads:[~2019-05-02 3:57 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 [this message]
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 ` [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=875zqt4igg.fsf@notabene.neil.brown.name \
--to=neilb@suse.com \
--cc=Patrick_Plagwitz@web.de \
--cc=agruenba@redhat.com \
--cc=amir73il@gmail.com \
--cc=andreas.gruenbacher@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 \
/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).