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From: Dominick Grift <>
To: Laurent Bigonville <>
Subject: Re: systemd --user for GDM started as unconfined_t instead of xdm_t
Date: Sun, 6 Oct 2019 11:41:56 +0200
Message-ID: <20191006094156.GB469820@brutus.lan> (raw)
In-Reply-To: <>

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On Sun, Oct 06, 2019 at 11:22:00AM +0200, Laurent Bigonville wrote:
> Hello,
> I discovered today that the GDM own processes are started as unconfined_t
> instead of xdm_t because systemd --user process itself is started in that
> context.
> This is probably related to:
> commit da156aea1e89a6ff6025be7e50c9c8173e5a6dcf
> Author: Chris PeBenito <>
> Date:   Fri Apr 19 11:50:59 2019 -0400
>     systemd: Add initial policy for systemd --user.
>     This is just a start; it does not cover all uses.
>     Signed-off-by: Chris PeBenito <>
> Was that expected and/or wanted?

It just means that gdm hooks into pam, and since 1. your __default__ id is set to unconfined_u and 2. you do not have a private id for gdm (and gnome-initial-setup) systemd will start gdm's systemd --user instance with unconfined_u:unconfined_r:unconfined_t.

One (ugly but arguable less ugly than the alternative) solution is to create a "xdm_u" and allow systemd to run a systemd --user instance on behalf of gdm with "xdm_u:system_r:xdm_t"

That way you can tell selinux that gdm's systemd --user instance should never transition out of xdm_u:system_r:xdm_t

echo "system_r:init_t:s0 system_r:xdm_t:s0" > /etc/selinux/TYPE/contexts/users/xdm_u

Then all processes in the gdm session should stay in xdm_t (but some processes will be associate with xdm_u and other with system_u).

You would probably also want to add to semanage.conf:

ignoredirs = /var/lib/gdm;/run/gnome-initial-setup

and make sure that selinux does not relabel /run/user/$(id -u gdm)

> Kind regards,
> Laurent Bigonville

Key fingerprint = 5F4D 3CDB D3F8 3652 FBD8 02D5 3B6C 5F1D 2C7B 6B02
Dominick Grift

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Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-06  9:22 Laurent Bigonville
2019-10-06  9:41 ` Dominick Grift [this message]
2019-10-06 10:01   ` Dominick Grift
2019-10-06 10:13     ` Dominick Grift

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