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 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 199DAEB64D8 for ; Wed, 21 Jun 2023 15:29:42 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qBzlI-0001VH-9d; Wed, 21 Jun 2023 11:28:48 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qBzlF-0001Ul-P5 for qemu-devel@nongnu.org; Wed, 21 Jun 2023 11:28:46 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qBzlE-0002AY-0u for qemu-devel@nongnu.org; Wed, 21 Jun 2023 11:28:45 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1687361322; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=wZPbb+s+LbsJ22ls7iNKmGcRkWQ1rRZhaV7GQHYSLKw=; b=SbcVVikQ/3ODa1/J9n+rP6P5cCDSM5a5qa5E2DtS/kIdnBpw6YD4YcqkTnte6B5/TqdK1d xHi/2OObyydzHbCsA7sUsff2PC/64MPf9n3lA2nhkR1KCqYqxH7EyzQB6Jpuk0nnJ0MYKF 2+lZwnoAroH7l85jdcImEEV9r5un3MI= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-88-YnAov_tSOFqhWjYNf9sVUA-1; Wed, 21 Jun 2023 11:28:38 -0400 X-MC-Unique: YnAov_tSOFqhWjYNf9sVUA-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 3985010504B4; Wed, 21 Jun 2023 15:28:36 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.44]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B04252166B32; Wed, 21 Jun 2023 15:28:35 +0000 (UTC) Date: Wed, 21 Jun 2023 16:28:33 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Christian Schoenebeck Cc: qemu-devel@nongnu.org, Greg Kurz Subject: Re: [PATCH v3] 9pfs: deprecate 'proxy' backend Message-ID: References: <54432347.sjJ5l9EzYk@silver> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <54432347.sjJ5l9EzYk@silver> User-Agent: Mutt/2.2.9 (2022-11-12) X-Scanned-By: MIMEDefang 3.1 on 10.11.54.6 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Wed, Jun 21, 2023 at 04:27:04PM +0200, Christian Schoenebeck wrote: > On Wednesday, June 21, 2023 3:46:39 PM CEST Daniel P. Berrangé wrote: > > On Sat, Jun 10, 2023 at 03:39:44PM +0200, Christian Schoenebeck wrote: > > > +``-fsdev proxy`` and ``-virtfs proxy`` (since 8.1) > > > +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > > + > > > +The 9p ``proxy`` filesystem backend driver has been deprecated and will be > > > +removed in a future version of QEMU. Please use ``-fsdev local`` or > > > +``-virtfs local`` for using the ``local`` 9p filesystem backend instead. > > > + > > > +The 9p ``proxy`` backend was originally developed as an alternative to the 9p > > > +``local`` backend. The idea was to enhance security by dispatching actual low > > > +level filesystem operations from 9p server (QEMU process) over to a separate > > > +process (the virtfs-proxy-helper binary). However this alternative never gained > > > +momentum. The proxy backend is much slower than the local backend, hasn't seen > > > +any development in years, and showed to be less secure, especially due to the > > > +fact that its helper daemon must be run as root, whereas with the local backend > > > +QEMU is typically run as unprivileged user and allows to tighten behaviour by > > > +mapping permissions et al. > > > > The fact that the helper daemon runs as root was actually an intentional > > design choice to improve security. When QEMU is running unprivileged, the > > 'local' backend is limited in what it can serve to stuff that is readable/ > > writable by the 'qemu' user account. > > > > Using the 'proxy' backend allowed that restriction to be lifted, such > > that it can serve files owned by arbitrary users. > > > > Yes, the 'proxy' backend is less secure than the 'local' backend in an > > unprivileged QEMU. It is massively more secure, however, than the 'local' > > backend in a QEMU process running as root, which was the only option if > > you need to serve files for many users. > > > > IOW, if someone is currently using the 'proxy' backend, the 'local' backend > > is quite likely NOT a viable alternative. > > Depends. Some people just want to dump few files between host <-> guest, they > should even be fine with unpriviliged 'passhthrough' security model with the > 'local' backend. > > For more complex use cases, you would probably transition to 'mapped' security > model with the 'local' backend. That's like transitioning from one file system > to another, mounting the two, copying over once, that's it. > > > I'm fine with deprecating this. In terms of messaging wrt replacements, > > we should highlight both the 9p 'local' backend, and virtiofsd as the > > two alternatives. The latter is likely the better choice (on linux > > hosts) for many. > > OK, I can add that to the deprecation doc, but you don't want that to be > added to all the runtime warnings as well, do you? I'd suggest we could do mention it briefly as an option at rutime, eg warn_report("'-virtfs proxy' is deprecated, use '-virtfs local' or virtiofs instead"); With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|