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Date: Mon, 16 May 2016 09:12:57 -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 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 :-) I'm happy to look with Djalal for commonalities. I did skim his patches before, and based on that all I really expect to find are things related to permission checks when ids don't map. The rest seems fundamentally different. Seth
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