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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 97F6CC433FE for ; Thu, 19 May 2022 09:46:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235840AbiESJqv (ORCPT ); Thu, 19 May 2022 05:46:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45002 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236230AbiESJqt (ORCPT ); Thu, 19 May 2022 05:46:49 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 6815769B58 for ; Thu, 19 May 2022 02:46:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1652953607; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=bMReF8cCrWNT+y8fLyYoHigFI6O30lF2NYiv8Us0yFg=; b=fDriS6nuUzFH4fytYTRgiN5ljsMdna59e3BLhhQ05PtgV/DHWdDuDQ1c5yoMJaIOKIvd08 ifU3HqenDUNUb4LULYpL+630ATT+ia70fn8AS0CBqybB5EtYPdDt/8fvw6E8gw/+BN6p6p yKtr3NGiOlub5bYNrTeyYg6wDenLbYk= 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-443-Fa9_pUzsMRCdUL7KDmAiGw-1; Thu, 19 May 2022 05:46:44 -0400 X-MC-Unique: Fa9_pUzsMRCdUL7KDmAiGw-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 7C264811E80; Thu, 19 May 2022 09:46:43 +0000 (UTC) Received: from localhost (unknown [10.39.193.61]) by smtp.corp.redhat.com (Postfix) with ESMTP id BFC4B401E9D; Thu, 19 May 2022 09:46:42 +0000 (UTC) Date: Thu, 19 May 2022 10:46:41 +0100 From: Stefan Hajnoczi To: Ming Lei Cc: Jens Axboe , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Harris James R , io-uring@vger.kernel.org, Gabriel Krisman Bertazi , ZiyangZhang , Xiaoguang Wang Subject: Re: [PATCH V2 0/1] ubd: add io_uring based userspace block driver Message-ID: References: <20220517055358.3164431-1-ming.lei@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="6MbhIVNGz8/JKSi2" Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.85 on 10.11.54.10 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org --6MbhIVNGz8/JKSi2 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, May 19, 2022 at 10:42:22AM +0800, Ming Lei wrote: > On Wed, May 18, 2022 at 04:49:03PM +0100, Stefan Hajnoczi wrote: > > On Wed, May 18, 2022 at 08:53:54PM +0800, Ming Lei wrote: > > > On Wed, May 18, 2022 at 11:45:32AM +0100, Stefan Hajnoczi wrote: > > > > On Wed, May 18, 2022 at 03:09:46PM +0800, Ming Lei wrote: > > > > > On Tue, May 17, 2022 at 03:06:34PM +0100, Stefan Hajnoczi wrote: > > > > > > Here are some more thoughts on the ubd-control device: > > > > > >=20 > > > > > > The current patch provides a ubd-control device for processes w= ith > > > > > > suitable permissions (i.e. root) to create, start, stop, and fe= tch > > > > > > information about devices. > > > > > >=20 > > > > > > There is no isolation between devices created by one process an= d those > > > > >=20 > > > > > I understand linux hasn't device namespace yet, so can you share = the > > > > > rational behind the idea of device isolation, is it because ubd d= evice > > > > > is served by ubd daemon which belongs to one pid NS? Or the user = creating > > > > > /dev/ubdbN belongs to one user NS? > > > >=20 > > > > With the current model a process with access to ubd-control has con= trol > > > > over all ubd devices. This is not desirable for most container use = cases > > > > because ubd-control usage within a container means that container c= ould > > > > stop any ubd device on the system. > > > >=20 > > > > Even for non-container use cases it's problematic that two applicat= ions > > > > that use ubd can interfere with each other. If an application passe= s the > > > > wrong device ID they can stop the other application's device, for > > > > example. > > > >=20 > > > > I think it's worth supporting a model where there are multiple ubd > > > > daemons that are not cooperating/aware of each other. They should be > > > > isolated from each other. > > >=20 > > > Maybe I didn't mention it clearly, I meant the following model in las= t email: > > >=20 > > > 1) every user can send UBD_CMD_ADD_DEV to /dev/ubd-control > > >=20 > > > 2) the created /dev/ubdcN & /dev/udcbN are owned by the user who crea= tes > > > it > >=20 > > How does this work? Does userspace (udev) somehow get the uid/gid from > > the uevent so it can set the device node permissions? >=20 > We can let 'ubd list' export the owner info, then udev may override the d= efault > owner with exported info. >=20 > Or it can be done inside devtmpfs_create_node() by passing ubd's uid/gid > at default. >=20 > For /dev/ubdcN, I think it is safe, since the driver is only > communicating with the userspace daemon, and both belong to same owner. > Also ubd driver is simple enough to get full audited. >=20 > For /dev/ubdbN, even though FS isn't allowed to mount, there is still > lots of kernel code path involved, and some code path may not be run > with unprivileged user before, that needs careful audit. >=20 > So the biggest problem is if it is safe to export block disk to unprivile= ged > user, and that is the one which can't be bypassed for any approach. Okay. 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