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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 934CCC43331 for ; Tue, 24 Mar 2020 13:13:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 734552098B for ; Tue, 24 Mar 2020 13:13:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727913AbgCXNNk (ORCPT ); Tue, 24 Mar 2020 09:13:40 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:50348 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727887AbgCXNNc (ORCPT ); Tue, 24 Mar 2020 09:13:32 -0400 Received: from pps.filterd (m0098419.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 02OD5sRn036681 for ; Tue, 24 Mar 2020 09:13:31 -0400 Received: from e06smtp02.uk.ibm.com (e06smtp02.uk.ibm.com [195.75.94.98]) by mx0b-001b2d01.pphosted.com with ESMTP id 2ywbuvdapf-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 24 Mar 2020 09:13:31 -0400 Received: from localhost by e06smtp02.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 24 Mar 2020 13:13:28 -0000 Received: from b06avi18878370.portsmouth.uk.ibm.com (9.149.26.194) by e06smtp02.uk.ibm.com (192.168.101.132) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 24 Mar 2020 13:13:25 -0000 Received: from d06av21.portsmouth.uk.ibm.com (d06av21.portsmouth.uk.ibm.com [9.149.105.232]) by b06avi18878370.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 02ODDQPd38273506 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 24 Mar 2020 13:13:26 GMT Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id F32EC52052; Tue, 24 Mar 2020 13:13:25 +0000 (GMT) Received: from pomme.local (unknown [9.145.51.233]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTP id 4D46752051; Tue, 24 Mar 2020 13:13:25 +0000 (GMT) Subject: Re: [PATCH 1/2] KVM: PPC: Book3S HV: check caller of H_SVM_* Hcalls To: Greg Kurz , Paul Mackerras Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, kvm-ppc@vger.kernel.org, Bharata B Rao , Benjamin Herrenschmidt , Michael Ellerman References: <20200320102643.15516-1-ldufour@linux.ibm.com> <20200320102643.15516-2-ldufour@linux.ibm.com> <20200320132248.44b81b3b@bahia.lan> <20200323234323.GA5604@blackberry> <20200324130052.373fdf89@bahia.lan> From: Laurent Dufour Date: Tue, 24 Mar 2020 14:13:11 +0100 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200324130052.373fdf89@bahia.lan> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 20032413-0008-0000-0000-0000036302DC X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 20032413-0009-0000-0000-00004A846EFC Message-Id: <4dc4bb94-9ddd-30f7-3b4c-0b8439119349@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.645 definitions=2020-03-24_05:2020-03-23,2020-03-24 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 priorityscore=1501 lowpriorityscore=0 malwarescore=0 bulkscore=0 adultscore=0 mlxscore=0 phishscore=0 impostorscore=0 mlxlogscore=999 suspectscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2003240067 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Le 24/03/2020 à 13:00, Greg Kurz a écrit : > On Tue, 24 Mar 2020 10:43:23 +1100 > Paul Mackerras wrote: > >> On Fri, Mar 20, 2020 at 01:22:48PM +0100, Greg Kurz wrote: >>> On Fri, 20 Mar 2020 11:26:42 +0100 >>> Laurent Dufour wrote: >>> >>>> The Hcall named H_SVM_* are reserved to the Ultravisor. However, nothing >>>> prevent a malicious VM or SVM to call them. This could lead to weird result >>>> and should be filtered out. >>>> >>>> Checking the Secure bit of the calling MSR ensure that the call is coming >>>> from either the Ultravisor or a SVM. But any system call made from a SVM >>>> are going through the Ultravisor, and the Ultravisor should filter out >>>> these malicious call. This way, only the Ultravisor is able to make such a >>>> Hcall. >>> >>> "Ultravisor should filter" ? And what if it doesn't (eg. because of a bug) ? >>> >>> Shouldn't we also check the HV bit of the calling MSR as well to >>> disambiguate SVM and UV ? >> >> The trouble with doing that (checking the HV bit) is that KVM does not >> expect to see the HV bit set on an interrupt that occurred while we >> were in the guest, and if it is set, it indicates a serious problem, >> i.e. that an interrupt occurred while we were in the code that >> transitions from host context to guest context, or from guest context >> to host context. In those cases we don't know how much of the >> transition has been completed and therefore whether we have guest >> values or host values in the CPU registers (GPRs, FPRs/VSRs, SPRs). >> If we do see HV set then KVM reports a severe error to userspace which >> should cause userspace to terminate the guest. >> >> Therefore the UV should *always* have the HV bit clear in HSRR1/SRR1 >> when transitioning to KVM. >> > > Indeed... thanks for the clarification. So I guess we'll just assume > that the UV doesn't reflect these SVM specific hcalls if they happened > to be issued by the guest then. As mentioned in the series's description: "It is assumed that the UV will filtered out such Hcalls made by a malicious SVM." > Cheers, > > -- > Greg > >> Paul. >