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 lists1p.gnu.org (lists1p.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 C9301C43602 for ; Tue, 7 Jul 2026 17:52:39 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1wh9xF-0006xD-60; Tue, 07 Jul 2026 13:51:33 -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 1wh9wV-000636-9H for qemu-devel@nongnu.org; Tue, 07 Jul 2026 13:50:47 -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 1wh9wT-0001OV-Ij for qemu-devel@nongnu.org; Tue, 07 Jul 2026 13:50:47 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1783446644; 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=XdVTva91bwLGqqzohpnP/TPz/kRPi9v0JlFPYmELZg0=; b=Hn4VpIJ5fJEgIlpr3iVzVmfRjYrwGsqU6VeZdCFPaXbthoxBJaNu8u/wzSwDfisaOAM0fg phApTHbVqVhDoZzr06sx7eSOtoyccTTn2w2LDPOjRiW8xWjgmcnPWCrXWw4W5RhbpUnqw4 nnJ+fTT59EhzZNBCPWaIyGRJHsm2jJg= 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-135-ua2GnAByNE6leebZzbEniw-1; Tue, 07 Jul 2026 13:50:41 -0400 X-MC-Unique: ua2GnAByNE6leebZzbEniw-1 X-Mimecast-MFC-AGG-ID: ua2GnAByNE6leebZzbEniw_1783446640 Received: from mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.95]) (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 88EE419540E5; Tue, 7 Jul 2026 17:50:40 +0000 (UTC) Received: from berrange.com (unknown [10.44.33.142]) by mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id D61E33692F; Tue, 7 Jul 2026 17:50:37 +0000 (UTC) From: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= To: qemu-devel@nongnu.org Cc: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= , Pierrick Bouvier , Thomas Huth , =?UTF-8?q?C=C3=A9dric=20Le=20Goater?= , "Michael S. Tsirkin" , Mauro Matteo Cascella Subject: [PULL 4/4] docs: outline some guidelines for security classification Date: Tue, 7 Jul 2026 18:50:27 +0100 Message-ID: <20260707175027.3029620-5-berrange@redhat.com> In-Reply-To: <20260707175027.3029620-1-berrange@redhat.com> References: <20260707175027.3029620-1-berrange@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.6 on 10.30.177.95 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: 8 X-Spam_score: 0.8 X-Spam_bar: / X-Spam_report: (0.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.445, 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_H3=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-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Beyond the overall virt/non-virt use case classification, there are a number of scenarios which we have decided will not be treated as security issues. Start to document some of these to give consistency in our treatment of incoming disclosures. Reviewed-by: Thomas Huth Reviewed-by: Cédric Le Goater Acked-by: Michael S. Tsirkin Reviewed-by: Mauro Matteo Cascella Signed-off-by: Daniel P. Berrangé --- docs/system/security.rst | 63 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 63 insertions(+) diff --git a/docs/system/security.rst b/docs/system/security.rst index 53992048e6..52bbf0cc7a 100644 --- a/docs/system/security.rst +++ b/docs/system/security.rst @@ -75,6 +75,69 @@ Bugs affecting the non-virtualization use case are not considered security bugs at this time. Users with non-virtualization use cases must not rely on QEMU to provide guest isolation or any security guarantees. +Security boundary scope +''''''''''''''''''''''' + +Even where a flaw affects the virtualization use case described above, +not all scenarios will be considered in scope. The following guidelines +are used to evaluate whether to apply the full security process, or treat +an issue as a normal bug. + +* **assert** / **abort**. If triggering the code path requires kernel + privileges (or root account access) in the guest, asserts/aborts in + QEMU are a self inflicted denial of service. These will **not** be + treated as security flaws, at most hardening bugs. If triggering the + code path can be done by an unprivileged guest OS account, this + **may** justify handling as a security bug. + +* **vhost-user/vfio-user backends**. The backend processes have + shared memory regions co-mapped with the QEMU process. The intent + of the process separation is operational resilience & flexibility + and allowing for independent software suppliers. There is not + considered to be security boundary between QEMU and the vhost-user + & vfio-user backends. Thus flaws in the backends which can cause + crashes / undesirable behaviour in QEMU will **not** be treated as + security flaws, but should be fixed as hardening bugs. + +* **memory allocation bounds**. There are many ways in which a QEMU + process can legitimately consume an amount of memory that is + significantly larger than the assigned guest RAM. QEMU's worst + case memory usage should be considered effectively unbounded. As + such the QEMU deployment on the host should account for the + possibility of large memory peaks and apply countermeasures to + provide continuity of host operations. It is typical for the Linux + OOM killer to reap the process triggering host memory overcommit + in the case of exccessive usage, offering a degree of protection. + As such, bugs which can lead to excessive/unbounded memory allocations + will usually not be classified as security flaws, but should be + fixed as hardening bugs. + +* **degraded guest behaviour**. There are a set of bugs which can + lead guest hardware devices to misbehave. For example, a flawed + virtual IOMMU operation may not offer the guest device isolation + that would otherwise be expected. If a guest triggered exploit + requires kernel privileges (or root account access), and leads + to sub-optimal behaviour of the virtual device this is considered + a self inflicted service degradation. These will **not** be + treated as security flaws, at most hardening bugs. If triggering + the code path can be done by an unprivileged guest OS account, + this may justify handling as a security bug. + +* **nested virtualization**. The scope for nested virtualization + is to prevent a level 2 guest from breaking out into a level + 1 guest. As noted above, a number of scenarios exclude security + handling for flaws only exploitable by the guest kernel / root + account with affect the guest's own service/availability. In the + context of nested virtualization with PCI device assignment, it + may may be possible for a level 2 guest kernel to trigger flaws + that affect the level 0 QEMU process. While these bugs should be + fixed, they will not be triaged as security flaws at this time. + +* **low severity impact**. As a catch all rule, issues which + are judged to have a "low" severity impact on the system will + usually not justify handling as security bugs, nor assignment + of CVEs. They will be fixed as routine bugs when time allows. + Architecture ------------ -- 2.55.0