From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7DAC6C433FE for ; Wed, 22 Sep 2021 15:34:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 63C1660F4C for ; Wed, 22 Sep 2021 15:34:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236451AbhIVPgS (ORCPT ); Wed, 22 Sep 2021 11:36:18 -0400 Received: from mail.kernel.org ([198.145.29.99]:49670 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236429AbhIVPgR (ORCPT ); Wed, 22 Sep 2021 11:36:17 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 806EF61168; Wed, 22 Sep 2021 15:34:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1632324887; bh=xFQo9lM17aSuzFSISevtYQSbPe53mGBV8+WNabxdSM4=; h=In-Reply-To:References:Date:From:To:Cc:Subject:From; b=CGYxEmVvdGglQjpPG2tO8ZpeKdFGhE7N2qSVJzoQRy3lFyu6dbPp5xYE203OosxuE ktOOqgL7JPKq1dDHn3iwxcOIQqxZAZQfh70hsg3hNqdOvWmcr93YHNhFYWU1atmbym XeJHSxkNtWib1xArlzV5AaGcUzusp7S/uAyzh3wPovBXyAq/ky++121J/g0pr7air3 YHhn56Cr5wspORIUL0vSEVqOzNIaisZ+jWgJ9pp08AgIFbQj9JnBQxJP9x2nNutKmA 04TOW1ZJ4WdkxZ6LD7IolJuHYl2SXRX70ROMUO0w/iCfmh88g4XUik/D4jgEnkuDvX Hltj0KwYG2dng== Received: from compute6.internal (compute6.nyi.internal [10.202.2.46]) by mailauth.nyi.internal (Postfix) with ESMTP id A360627C0054; Wed, 22 Sep 2021 11:34:45 -0400 (EDT) Received: from imap48 ([10.202.2.98]) by compute6.internal (MEProxy); Wed, 22 Sep 2021 11:34:45 -0400 X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvtddrudeijedgkeelucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmne cujfgurhepofgfggfkjghffffhvffutgfgsehtqhertderreejnecuhfhrohhmpedftehn ugihucfnuhhtohhmihhrshhkihdfuceolhhuthhosehkvghrnhgvlhdrohhrgheqnecugg ftrfgrthhtvghrnhepvdelheejjeevhfdutdeggefftdejtdffgeevteehvdfgjeeiveei ueefveeuvdetnecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehmrghilhhfrh homheprghnugihodhmvghsmhhtphgruhhthhhpvghrshhonhgrlhhithihqdduudeiudek heeifedvqddvieefudeiiedtkedqlhhuthhopeepkhgvrhhnvghlrdhorhhgsehlihhnuh igrdhluhhtohdruhhs X-ME-Proxy: Received: by mailuser.nyi.internal (Postfix, from userid 501) id E87CF21E0062; Wed, 22 Sep 2021 11:34:44 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface User-Agent: Cyrus-JMAP/3.5.0-alpha0-1302-gc62ab821ef-fm-20210921.001-gc62ab821 Mime-Version: 1.0 Message-Id: <59e230b3-0e85-42ff-84a8-6b30ad0719d8@www.fastmail.com> In-Reply-To: <20210922122523.72ypzg4pm2x6nkod@wittgenstein> References: <705fde50-37a6-49ed-b9c2-c9107cd88189@t-8ch.de> <20210916092719.v4pkhhugdiq7ytcp@wittgenstein> <2ebf1a9d-77d5-472b-a99a-b141654725da@www.fastmail.com> <6eff0e8a-4965-437d-9273-1d9d73892e1a@t-8ch.de> <8cbf0703-5734-4e92-a6cc-12de69094f95@t-8ch.de> <20210922122523.72ypzg4pm2x6nkod@wittgenstein> Date: Wed, 22 Sep 2021 08:34:23 -0700 From: "Andy Lutomirski" To: "Christian Brauner" Cc: "Luis Chamberlain" , =?UTF-8?Q?Thomas_Wei=C3=9Fschuh?= , "Linux API" , "Linux Kernel Mailing List" , "Jessica Yu" Subject: Re: [RFC] Expose request_module via syscall Content-Type: text/plain;charset=utf-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 22, 2021, at 5:25 AM, Christian Brauner wrote: > On Mon, Sep 20, 2021 at 11:36:47AM -0700, Andy Lutomirski wrote: >> On Mon, Sep 20, 2021 at 11:16 AM Luis Chamberlain = wrote: >> > >> > On Mon, Sep 20, 2021 at 04:51:19PM +0200, Thomas Wei=C3=9Fschuh wro= te: >>=20 >> > > > Do you mean it literally invokes /sbin/modprobe? If so, hookin= g this >> > > > at /sbin/modprobe and calling out to the container manager seem= s like >> > > > a decent solution. >> > > >> > > Yes it does. Thanks for the idea, I'll see how this works out. >> > >> > Would documentation guiding you in that way have helped? If so >> > I welcome a patch that does just that. >>=20 >> If someone wants to make this classy, we should probably have the >> container counterpart of a standardized paravirt interface. There >> should be a way for a container to, in a runtime-agnostic way, issue >> requests to its manager, and requesting a module by (name, Linux >> kernel version for which that name makes sense) seems like an >> excellent use of such an interface. > > I always thought of this in two ways we currently do this: > > 1. Caller transparent container manager requests. > This is the seccomp notifier where we transparently handle syscalls > including intercepting init_module() where we parse out the module = to > be loaded from the syscall args of the container and if it is > allow-listed load it for the container otherwise continue the sysca= ll > letting it fail or failing directly through seccomp return value. Specific problems here include aliases and dependencies. My modules.ali= as file, for example, has: alias net-pf-16-proto-16-family-wireguard wireguard If I do modprobe net-pf-16-proto-16-family-wireguard, modprobe parses so= me files in /lib/modules/`uname -r` and issues init_module() asking for = 'wireguard'. So hooking init_module() is at the wrong layer -- for that= to work, the container's /sbin/modprobe needs to already have figured o= ut that the desired module is wireguard and have a .ko for it. > > 2. A process in the container explicitly calling out to the container > manager. > One example how this happens is systemd-nspawn via dbus messages > between systemd in the container and systemd outside the container = to > e.g. allocate a new terminal in the container (kinda insecure but > that's another issue) or other stuff. > > So what was your idea: would it be like a device file that could be > exposed to the container where it writes requestes to the container > manager? What would be the advantage to just standardizing a socket > protocol which is what we do for example (it doesn't do module loading > of course as we handle that differently): My idea is standardizing *something*. I think it would be nice if, for = example, distros could ship a /sbin/modprobe that would do the right thi= ng inside any compliant container runtime as well as when running outsid= e a container. I suppose container managers could also bind-mount over /sbin/modprobe, = but that's more intrusive.