linux-kernel - Re: [RFC v2 PATCH 0/8] VFS:userns: support portable root filesystems

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Date:	Mon, 16 May 2016 13:25:27 -0500
From:	Seth Forshee <seth.forshee@...onical.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	James Bottomley <James.Bottomley@...senPartnership.com>,
	Djalal Harouni <tixxdz@...il.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Chris Mason <clm@...com>, tytso@....edu,
	Serge Hallyn <serge.hallyn@...onical.com>,
	Josh Triplett <josh@...htriplett.org>,
	Andy Lutomirski <luto@...nel.org>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	Dongsu Park <dongsu@...ocode.com>,
	David Herrmann <dh.herrmann@...glemail.com>,
	Miklos Szeredi <mszeredi@...hat.com>,
	Alban Crequy <alban.crequy@...il.com>,
	Dave Chinner <david@...morbit.com>
Subject: Re: [RFC v2 PATCH 0/8] VFS:userns: support portable root filesystems

On Mon, May 16, 2016 at 11:42:46AM -0500, Eric W. Biederman wrote:
> Seth Forshee <seth.forshee@...onical.com> writes:
> 
> > On Sat, May 14, 2016 at 09:21:55PM -0500, Eric W. Biederman wrote:
> >>   I have slowly been working with Seth Forshee on these issues as
> >>   the last thing I want is to introduce more security bugs right now.
> >>   Seth being a braver man than I am has already merged his changes into
> >>   the Ubuntu kernel.
> >
> > Maybe not quite so brave as you think. I also threw on a patch to
> > disable the feature unless explicitly enabled by a sys admin.
> >
> >> James I think you are missing the fact that all filesystems already have
> >> the make_kuid and make_kgid calls right where the data comes off disk,
> >> and the from_kuid and from_kgid calls right where the on-disk data is
> >> being created just before it goes on disk.  Which means that the actual
> >> impact on filesystems of the translation is trivial.
> >
> > It is fairly simple but a there's bit more that just id conversions to
> > change. With ext4 I found that there were mount options which needed to
> > be restricted, some capability checks to update, and access to external
> > journal devices must be checked. In all it wasn't a whole lot of changes
> > to the filesystem though. Fuse was a bit more involved, but the
> > complexities there won't apply to other filesystems.
> >
> >> Djalal if you could work with Seth I think that would be very useful.  I
> >> know I am dragging my heels there but I really hope I can dig in and get
> >> everything reviewed and merged soonish.
> >
> > That would make me very happy :-)
> 
> It has missed this merge window :( But I am hoping with am aiming to
> review them and get your patches (or modified versions of your patches)
> into my tree as soon after rc1 as humanly possible.
> 
> Part of that will have to be the fix for mqueuefs, that Docker just hit.

Yeah, I've got a patch that's been tested to fix the bug, so I'll send
new patches which include that before long.

Seth