From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lists1p.gnu.org (lists1p.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9ADB2606A31F for ; Thu, 29 Oct 2026 14:15:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=XFcIyPoe Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1xMQu1-0001rY-B7; Thu, 29 Oct 2026 10:14:49 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1xMQtb-0001py-BJ for qemu-devel@nongnu.org; Thu, 29 Oct 2026 10:14:29 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1xMQtX-0005EK-Of for qemu-devel@nongnu.org; Thu, 29 Oct 2026 10:14:23 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1793283253; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=KQ2CJ5p07QnKSMBt6DqrLBt42EO8sQJwRt7FIkOcEw0=; b=XFcIyPoeWKLN3rV/31Bvj2A1HQ3JYJrwk69n+uvdYf+kQmMKlKvq4+Z+Hl+gzKeggodDPd +cV4cQpm52A94NJHUSkdDllNIrjtBWAWVukx2sTx33h8eqMv25NryLoyErB9/aKV9Zl9sn HRhCuM8oZRr3kkpxatmKrEjxj6rTgtk= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-455-Uz3zfkIsPKmCIOQ7xqxt9w-1; Thu, 29 Oct 2026 10:14:00 -0400 X-MC-Unique: Uz3zfkIsPKmCIOQ7xqxt9w-1 X-Mimecast-MFC-AGG-ID: Uz3zfkIsPKmCIOQ7xqxt9w_1793283240 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 373EA19541A0 for ; Thu, 29 Oct 2026 14:13:54 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.44.22.2]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id A79CA1955F08 for ; Thu, 29 Oct 2026 14:13:53 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 39DB521E6A04; Thu, 29 Oct 2026 15:13:51 +0100 (CET) From: Markus Armbruster To: Daniel P. =?utf-8?Q?Berrang=C3=A9?= Cc: qemu-devel@nongnu.org Subject: Re: [PATCH 7/8] qemu-options: document -compat insecure-input parameter In-Reply-To: ("Daniel P. =?utf-8?Q?Berrang?= =?utf-8?Q?=C3=A9=22's?= message of "Thu, 29 Oct 2026 10:56:30 +0000") References: <20261028133603.1893289-1-berrange@redhat.com> <20261028133603.1893289-8-berrange@redhat.com> <871p99gfrf.fsf@pond.sub.org> Date: Thu, 29 Oct 2026 15:13:51 +0100 Message-ID: <87wlr0bnmo.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 5 X-Spam_score: 0.5 X-Spam_bar: / X-Spam_report: (0.5 / 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, GB_FAKE_RF=0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_SBL_CSS=3.335, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Archive: List-Post: List-Help: List-Subscribe: , Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org X-Spam-Status: No, score=-17.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 Daniel P. Berrang=C3=A9 writes: > On Thu, Oct 29, 2026 at 07:52:36AM +0100, Markus Armbruster wrote: >> Daniel P. Berrang=C3=A9 writes: >>=20 >> > This adds documentation for the previously added 'insecure-input' >> > parameter to -compat, which controls policy for insecure >> > configuration requests. >> > >> > Signed-off-by: Daniel P. Berrang=C3=A9 >> > --- >> > qemu-options.hx | 22 +++++++++++++++++++++- >> > 1 file changed, 21 insertions(+), 1 deletion(-) >> > >> > diff --git a/qemu-options.hx b/qemu-options.hx >> > index 16d9c6c9072..0487e74bb3e 100644 >> > --- a/qemu-options.hx >> > +++ b/qemu-options.hx >> > @@ -4696,7 +4696,9 @@ DEF("compat", HAS_ARG, QEMU_OPTION_compat, >> > "-compat [deprecated-input=3Daccept|reject|crash|warn][,deprecate= d-output=3Daccept|hide]\n" >> > " Policy for handling deprecated management interf= aces\n" >> > "-compat [unstable-input=3Daccept|reject|crash|warn][,unstable-ou= tput=3Daccept|hide]\n" >> > - " Policy for handling unstable management interfac= es\n", >> > + " Policy for handling unstable management interfac= es\n" >> > + "-compat [insecure-input=3Daccept|reject|crash|warn]\n" >> > + " Policy for handling requests for insecure config= uration requests\n", >> > QEMU_ARCH_ALL) >> > SRST >> > ``-compat [deprecated-input=3D][,deprecated-output=3D]`` >> > @@ -4734,6 +4736,24 @@ SRST >> > Suppress unstable command results and events >> >=20=20 >> > Limitation: covers only syntactic aspects of QMP. >> > + >> > +``-compat [insecure-input=3D] >> > + Set policy for handling requests for insecure configuration >> > + requests: >> > + >> > + ``insecure-input=3Daccept`` (default) >> > + Accept insecure configurations requests silently >> > + ``insecure-input=3Dwarn`` >> > + Accept insecure configuration requests with warning on stderr >> > + ``insecure-input=3Dreject`` >> > + Reject insecure configuration requests >> > + ``insecure-input=3Dcrash`` >> > + Crash on insecure configuration requests >> > + >> > + Limitation: an insecure configuration is one where QEMU has >> > + not intended to provide a security boundary to protect against >>=20 >> "Where QEMU has not intended to provide" sounds odd to me. Mind, I'm >> not a native speaker. "Where QEMU does not provide". > > Yeah, that language choice was me by pessimistic expecting that > QEMU is full of undiscovered flaws. I'll change to what you > suggested. > >> > + malicious usage. Covers only QOM types for devices, machine types >> > + and accelerators. >>=20 >> The policy check is in >>=20 >> * qemu_create_machine(), which covers machine creation. >>=20 >> * do_configure_accelerator(), which covers accelerator creation. >>=20 >> * qdev_device_add_from_qdict(), which covers *some* device creation: >>=20 >> * device_add and -device always >>=20 >> * Half of -audio model=3Dhda: covers the "intel-hda" device, but not t= he >> "hda-duplex" device. See intel_hda_and_codec_init(). >>=20 >> * The "primary device" created in failover_hide_primary_device() for >> the virtio-net standby feature. >>=20 >> * The "usb-host" device device created in xen-usb.c for some reason. >>=20 >> There's plenty of device creation it doesn't cover. Isn't this >> problematic? I certainly expected it to cover *all* device creation! > > Yes, eventually, but not yet.... > >>=20 >> Say board code creates a certain onboard device with the usual low >> level interfaces like qdev_new() and qdev_realize(). Say we mark the >> onboard device insecure. The policy check doesn't apply. We need to >> manually mark the machine type insecure as well. Feels awfully prone >> to human error. >>=20 >> Moreover, what if the onboard device is configurable? Then the >> machine type may be secure unless you configure this insecure device. >> Marking the machine type would be too coarse. >>=20 >> Could we check policy in qdev_realize() instead? > > Yes and no. > > To make this a tractable problem I only wanted to add '.secure =3D true' > annotations for public facing types initially, so needed the check in > the device_add/-device code path only. > > This is sufficient to let us tell bug report filers to take their demo > command line and add > > '-compat insecure-input=3Dreject -nodfaults' > > as a pre-requisite for a bug being considered a security flaw > egligible for CVE handling. > > > If we put a check in qdev_realize(), then we need to add annotations > for *all* types, before the -compat insecure-input=3D.... option is > viable to use. That requires a much bigger effort to mark all types. > > In the 12.0 dev cycle, my intention is to > > a) Expand ".secure =3D true" markers to all parents of leaf node types > marked secure, and enforce them. > b) Expand ".secure =3D true" markers to all built-in devices that are > indirectly created by a leaf node type marked secure, when > -nodefaults is present > > Once (b) is done, then qdev_realize() will likely be the better place > to put the policy check. Let's see whether I got this. * A type can be known to be secure, known to be insecure, or unknown. * Exactly the types known to be secure are marked secure. Thus, the policy check must treat known to be insecure and unknown the same, which makes sense. * We start with all types unknown. * To move a type from unknown to known, we need to examine it. Examining all types in time for the next release is infeasible. Even examining all types usable with a useful set of machines is infeasible. What is feasible is examining a useful set of types available with certain user interfaces, so that's what we did. * We check the policy in these interfaces only. This lets users restrict these interfaces to known secure types, which is useful. * However, types created differently get a blanket exception. Not ideal, but no worse than before, unless the new policy creates a false sense of security. The best we can (and should) do about that is to clearly document the policy's current limitations. Right?