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Date:   Tue, 7 Sep 2021 17:40:31 -0400
From:   Vivek Goyal <vgoyal@redhat.com>
To:     Miklos Szeredi <miklos@szeredi.hu>
Cc:     "Dr. David Alan Gilbert" <dgilbert@redhat.com>,
        Andreas Gruenbacher <agruenba@redhat.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        virtio-fs-list <virtio-fs@redhat.com>,
        Daniel J Walsh <dwalsh@redhat.com>,
        Christian Brauner <christian.brauner@ubuntu.com>,
        casey.schaufler@intel.com,
        LSM <linux-security-module@vger.kernel.org>,
        SElinux list <selinux@vger.kernel.org>,
        Theodore Ts'o <tytso@mit.edu>,
        Giuseppe Scrivano <gscrivan@redhat.com>,
        "Fields, Bruce" <bfields@redhat.com>,
        Stephen Smalley <stephen.smalley.work@gmail.com>,
        Dave Chinner <david@fromorbit.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>
Subject: Re: [PATCH v3 0/1] Relax restrictions on user.* xattr
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On Mon, Sep 06, 2021 at 04:56:44PM +0200, Miklos Szeredi wrote:
> On Mon, 6 Sept 2021 at 16:39, Dr. David Alan Gilbert
> <dgilbert@redhat.com> wrote:
> 
> > IMHO the real problem here is that the user/trusted/system/security
> > 'namespaces' are arbitrary hacks rather than a proper namespacing
> > mechanism that allows you to create new (nested) namespaces and associate
> > permissions with each one.
> 
> Indeed.
> 
> This is what Eric Biederman suggested at some point for supporting
> trusted xattrs within a user namespace:
> 
> | For trusted xattrs I think it makes sense in principle.   The namespace
> | would probably become something like "trusted<ns-root-uid>.".
> 
> Theory sounds simple enough.  Anyone interested in looking at the details?

So this namespaced trusted.* xattr domain will basically avoid the need
to have CAP_SYS_ADMIN in init_user_ns, IIUC.  I guess this is better
than giving CAP_SYS_ADMIN in init_user_ns.

Vivek