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Re: [PATCH v2 RFC] userns: Convert xfs to use kuid/kgid where appropriat

To: Serge Hallyn <serge.hallyn@xxxxxxxxxx>
Subject: Re: [PATCH v2 RFC] userns: Convert xfs to use kuid/kgid where appropriate
From: Dwight Engen <dwight.engen@xxxxxxxxxx>
Date: Fri, 28 Jun 2013 12:16:21 -0400
Cc: Dave Chinner <david@xxxxxxxxxxxxx>, "Eric W. Biederman" <ebiederm@xxxxxxxxx>, xfs@xxxxxxxxxxx, Brian Foster <bfoster@xxxxxxxxxx>, "Michael Kerrisk (man-pages)" <mtk.manpages@xxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20130628152552.GB26841@sergelap>
Organization: Oracle Corporation
References: <20130620095410.1917d235@xxxxxxxxxx> <20130620220311.GT29376@dastard> <20130621111420.5592707e@xxxxxxxxxx> <20130624003316.GH29376@dastard> <20130624091035.6274800f@xxxxxxxxxx> <20130626020924.GD29376@dastard> <20130626173017.5100327a@xxxxxxxxxx> <20130626224410.GB28426@dastard> <20130627130205.GA4003@sergelap> <20130628015401.GG32195@dastard> <20130628152552.GB26841@sergelap>
On Fri, 28 Jun 2013 10:25:52 -0500
Serge Hallyn <serge.hallyn@xxxxxxxxxx> wrote:

> Quoting Dave Chinner (david@xxxxxxxxxxxxx):
> > On Thu, Jun 27, 2013 at 08:02:05AM -0500, Serge Hallyn wrote:
> > > Quoting Dave Chinner (david@xxxxxxxxxxxxx):
> > > > On Wed, Jun 26, 2013 at 05:30:17PM -0400, Dwight Engen wrote:
> > > > > On Wed, 26 Jun 2013 12:09:24 +1000
> > > > > Dave Chinner <david@xxxxxxxxxxxxx> wrote:
> > > > > > > We do need to decide on the di_uid that comes back from
> > > > > > > bulkstat. Right now it is returning on disk (==
> > > > > > > init_user_ns) uids. It looks to me like xfsrestore is
> > > > > > > using the normal vfs routines (chown,
> > > 
> > > I might not be helpful here, (as despite having used xfs for years
> > > I've not used these features) but feel like I should try based on
> > > what I see in the manpages.  Here is my understanding:
> > > 
> > > Assume you're a task in a child userns, where you have host uids
> > > 100000-110000 mapped to container uids 0-10000,
> > > 
> > > 1. bulkstat is an xfs_ioctl command, right?  It should return the
> > > mapped uids (0-10000).
> > > 
> > > 2. xfsdump should store the uids as seen in the caller's
> > > namespace.  If xfsdump is done from the container, the dump
> > > should show uids 0-10000.
> > 
> > So when run from within a namespace, it should filter and return
> > only inodes that match the uids/gids mapped into the namespace?
> 
> I would think they should all be returned, with uid/gid being -1.

I agree, so I think bulkstat should return the uids with
from_kuid_munged(current_user_ns(), VFS_I(ip)), so it returns the
same values that stat(2) would. This would mean callers in
init_user_ns see the same values they do today. Callers inside
a userns will see mapped values, but note that they have to be
CAP_SYS_ADMIN in init_user_ns, which I wouldn't expect to normally be
the case.

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