From mboxrd@z Thu Jan  1 00:00:00 1970
From: Alban Crequy <alban.crequy-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH 2/2] user_namespaces.7: Update the documention to reflect
	the fixes for negative groups
Date: Mon, 2 Feb 2015 22:31:08 +0100
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To: "Eric W. Biederman" <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
Cc: linux-man <linux-man-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Kees Cook <keescook-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>, Linux API <linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Linux Containers <containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>, Josh Triplett <josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org>, stable <stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Kenton Varda <kenton-AuYgBwuPrUQTaNkGU808tA@public.gmane.org>, LSM <linux-security-module-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Michael Kerrisk-manpages <mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Richard Weinberger <richard-/L3Ra7n9ekc@public.gmane.org>, Casey Schaufler <casey-iSGtlc1asvQWG2LlvL+J4A@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org>
List-Id: linux-api@vger.kernel.org

Hello,

Thanks for updating the man page.

On 12 December 2014 at 22:54, Eric W. Biederman <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> wrote:
(...)
> Furthermore to preserve in some form the useful applications that have
> been setting gid_map without privilege the file /proc/[pid]/setgroups
> was added to allow disabling setgroups.  With the setgroups system
> call permanently disabled in a user namespace it again becomes safe to
> allow writes to gid_map without privilege.
>
> Here is my meager attempt to update user_namespaces.7 to reflect these
> issues.

The program userns_child_exec.c in user_namespaces.7 should be updated
to write in /proc/.../setgroups, near the line:
/* Update the UID and GID maps in the child */

Otherwise, the example given in the manpage does not work:
$ ./userns_child_exec -p -m -U -M '0 1000 1' -G '0 1000 1' bash

Cheers,
Alban