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 28B50C79F83 for ; Fri, 4 Sep 2026 11:01:52 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1x2ReX-0004dj-JJ; Fri, 04 Sep 2026 07:00:13 -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 1x2ReW-0004dV-Aj for qemu-devel@nongnu.org; Fri, 04 Sep 2026 07:00:12 -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 1x2ReU-0007rE-P2 for qemu-devel@nongnu.org; Fri, 04 Sep 2026 07:00:12 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1788519610; 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=FljOUZcrDxLcSEtdGZg2L7bnzs/rlfsiHLxsLO2MQAk=; b=GHteN/mThCl/uVCxSm23RjA8Q/Uia5mxqBCt71w3404R957EcQe9HYtxtg0wVOo8JyBPqi THGH09DWYXvYnj06uZdUS4p2vZs9VUXM2mj5+VkLw5BMkWF6dk4TJ6wtzGsVZoeAt+miDY 94tkj+FT31mYIQw0UH13q3YKYLbQq1E= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-318-jsqfwCQgPES8Wa8pJuNL1Q-1; Fri, 04 Sep 2026 07:00:05 -0400 X-MC-Unique: jsqfwCQgPES8Wa8pJuNL1Q-1 X-Mimecast-MFC-AGG-ID: jsqfwCQgPES8Wa8pJuNL1Q_1788519604 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (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-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 66C54188698A; Fri, 4 Sep 2026 11:00:04 +0000 (UTC) Received: from berrange.csb (headnet03.pony-001.prod.iad2.dc.redhat.com [10.2.32.114]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id B952A1801AEA; Fri, 4 Sep 2026 11:00:02 +0000 (UTC) From: =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= To: qemu-devel@nongnu.org Cc: =?UTF-8?q?Alex=20Benn=C3=A9e?= , Pierrick Bouvier , devel@lists.libvirt.org, =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= , Paolo Bonzini , =?UTF-8?q?Daniel=20P=2E=20Berrang=C3=A9?= Subject: [PULL 13/13] docs/system/security: exclude uninitialized stack variables as bugs Date: Fri, 4 Sep 2026 11:59:29 +0100 Message-ID: <20260904105929.3450663-14-berrange@redhat.com> In-Reply-To: <20260904105929.3450663-1-berrange@redhat.com> References: <20260904105929.3450663-1-berrange@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 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_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 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: 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 The -ftrivial-auto-var-init=zero usage guarantees implicit zero initializers for all stack variables. Thus most bug reports relying on undefined behaviour from lack of variable initialization will not be security issues, or even bugs. Reviewed-by: Marc-André Lureau Signed-off-by: Daniel P. Berrangé --- docs/system/security.rst | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/docs/system/security.rst b/docs/system/security.rst index af626a4230..8c42d1a6d8 100644 --- a/docs/system/security.rst +++ b/docs/system/security.rst @@ -143,6 +143,16 @@ an issue as a normal bug. which case plain manipulation of the stream is not considered as an attack vector. +* **uninitialized stack variables**. If the bug scenario relies on + undefined behaviour from stack variables that lack explicit + initialization, it will not usually be considered a security flaw. + The build system adds '-ftrivial-auto-var-init=zero', which is + available in both the supported compilers (GCC and CLang) and + ensures all stack variables have implicit zero-initializers. + This eliminates undefined behaviour and usually gives the + correct desired initialization value, eliminating most of the + bug scenarios wrt uninitialized stack variables. + * **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 -- 2.55.0