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 X-Spam-Level: X-Spam-Status: No, score=-7.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 48C87C433E0 for ; Thu, 21 Jan 2021 15:10:17 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id EC43623A3A for ; Thu, 21 Jan 2021 15:10:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EC43623A3A Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.72177.129716 (Exim 4.92) (envelope-from ) id 1l2bb0-0004Sw-D1; Thu, 21 Jan 2021 15:10:02 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 72177.129716; Thu, 21 Jan 2021 15:10:02 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1l2bb0-0004S1-9F; Thu, 21 Jan 2021 15:10:02 +0000 Received: by outflank-mailman (input) for mailman id 72177; Thu, 21 Jan 2021 15:10:00 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1l2bay-0004IF-Q4 for xen-devel@lists.xen.org; Thu, 21 Jan 2021 15:10:00 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id c1735042-181f-4fa6-85c0-c3b62161bb2d; Thu, 21 Jan 2021 15:09:59 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id EC12CAB7A; Thu, 21 Jan 2021 15:09:58 +0000 (UTC) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: c1735042-181f-4fa6-85c0-c3b62161bb2d X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1611241799; h=from:from:reply-to: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=jmaBHCPbyL5gzfHDJrIsU6Xk0dPmwpGxNzCreX7mgXQ=; b=QUiuEdB0lEFU4H9eKvsxEGCbM0f88naQeIj7CXKnyOoOGlBvXIxMnJXYqTOAPVpG96PJFQ q5r8++j0V9JfD0QDKDGtsQjw62VIf54glCudwwtWui7Rv4plbPkk2COckvoTxzqECfDbfo rYyeQ2aK6/tnWJWGUcoxVKxm3oqUtxw= Subject: Re: Xen Security Advisory 360 v1 - IRQ vector leak on x86 To: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= Cc: xen-devel@lists.xen.org, =?UTF-8?Q?Marek_Marczykowski-G=c3=b3recki?= References: <20210121142012.GB1592@mail-itl> <20210121143440.xucstdfws4ymtete@Air-de-Roger> <2d073bc8-418e-2b8d-9ff7-76b932f829b1@suse.com> <20210121150538.rliqx26wj2bvteuu@Air-de-Roger> From: Jan Beulich Message-ID: <92b4ee0e-fb34-9b7d-eb2e-fa14a514e0b3@suse.com> Date: Thu, 21 Jan 2021 16:09:58 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 MIME-Version: 1.0 In-Reply-To: <20210121150538.rliqx26wj2bvteuu@Air-de-Roger> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit On 21.01.2021 16:05, Roger Pau Monné wrote: > On Thu, Jan 21, 2021 at 03:50:55PM +0100, Jan Beulich wrote: >> On 21.01.2021 15:34, Roger Pau Monné wrote: >>> On Thu, Jan 21, 2021 at 03:20:12PM +0100, Marek Marczykowski-Górecki wrote: >>>> On Thu, Jan 21, 2021 at 02:10:48PM +0000, Xen.org security team wrote: >>>>> Xen Security Advisory XSA-360 >>>>> >>>>> IRQ vector leak on x86 >>>>> >>>>> ISSUE DESCRIPTION >>>>> ================= >>>>> >>>>> A x86 HVM guest with PCI pass through devices can force the allocation >>>>> of all IDT vectors on the system by rebooting itself with MSI or MSI-X >>>>> capabilities enabled and entries setup. >>>> >>>> (...) >>>> >>>>> MITIGATION >>>>> ========== >>>>> >>>>> Not running HVM guests with PCI pass through devices will avoid the >>>>> vulnerability. Note that even non-malicious guests can trigger this >>>>> vulnerability as part of normal operation. >>>> >>>> Does the 'on_reboot="destroy"' mitigate the issue too? Or on_soft_reset? >>> >>> Kind of. Note you will still leak the in use vectors when the guest is >>> destroyed, but that would prevent the guest from entering a reboot >>> loop and exhausting all vectors on the system unless the admin starts >>> it again. >>> >>> In that case I think the premise of a guest 'rebooting itself' doesn't >>> apply anymore, since the guest won't be able to perform such >>> operation. >> >> And how exactly would an admin tell a guest from rebooting for >> fair reasons from one rebooting for malicious reasons? To me, >> setting 'on_reboot="destroy"' would imply there's then some >> other mechanism to restart the guest (possibly with some delay), >> or else a reboot attempt by this guest would effectively be a >> DoS to its users. > > Well, I would expect there are deployments or configurations that > simply don't expect (some) domains to reboot themselves. Ie: for > example you won't expect driver domains to restart themselves I think, > and hence you could safely use on_reboot="destroy" in that case to > mitigate a compromised driver domain from exploiting this > vulnerability. Otoh a driver domain may warrant 'oncrash="restart"', to limit downtime of depending domains. Or, like Xen does by default, a driver domain may invoke its own restart when crashed. Jan