From owner-freebsd-fs@freebsd.org Wed Sep 16 16:57:01 2015 Return-Path: Delivered-To: freebsd-fs@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id B85139CD6D9 for ; Wed, 16 Sep 2015 16:57:01 +0000 (UTC) (envelope-from crest@rlwinm.de) Received: from smtp.rlwinm.de (smtp.rlwinm.de [IPv6:2a01:4f8:201:31ef::e]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 7E0831D31 for ; Wed, 16 Sep 2015 16:57:01 +0000 (UTC) (envelope-from crest@rlwinm.de) Received: from crest.local (unknown [87.253.189.132]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.rlwinm.de (Postfix) with ESMTPSA id BA32F6621 for ; Wed, 16 Sep 2015 18:56:58 +0200 (CEST) Subject: Re: Neutered devices in jails (per FS flag?) To: freebsd-fs@freebsd.org References: From: Jan Bramkamp Message-ID: <55F99F5A.302@rlwinm.de> Date: Wed, 16 Sep 2015 18:56:58 +0200 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 16 Sep 2015 16:57:01 -0000 On 16/09/15 18:30, Kevin Day wrote: > We’re currently using jails to allow servers to copy backups of themselves to a central backup server. The problem we’re having is with mknod/devices. Currently jails don’t allow device files to be created, which makes sense - you don’t want them to be able to bypass the jail by opening /dev/kmem or something. We want jails to be able to create device files, just not be able to open/use them. > > Has anyone given any thought to changing this behavior? Allowing jails to create/manipulate device files, but not actually opening them? I.e. instead of returning EPERM on creating the device, instead return EPERM on opening it? This would likely need to be a filesystem flag, because jails still require some devices to work (a separate devfs mount or something). We could make the jail’s /dev read only or use devfs so those devices still work, but have the parent jail directory with a “noopendev” flag or something similar. > > Has anyone gone down this path before? There is no reason to backup device files on FreeBSD because FreeBSD uses a dynamic devfs. Backup the devfs rules and devfs.conf instead of the device files.