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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable 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 081ECC4332D for ; Fri, 20 Mar 2020 14:54:14 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (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 776AA2070A for ; Fri, 20 Mar 2020 14:54:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 776AA2070A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.ibm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 48kRcf4byLzDrJ7 for ; Sat, 21 Mar 2020 01:54:10 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=linux.ibm.com (client-ip=148.163.156.1; helo=mx0a-001b2d01.pphosted.com; envelope-from=ldufour@linux.ibm.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.ibm.com Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 48kRP34Lk9zDrJt for ; Sat, 21 Mar 2020 01:44:07 +1100 (AEDT) Received: from pps.filterd (m0098394.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 02KEXfLm038558 for ; Fri, 20 Mar 2020 10:44:03 -0400 Received: from e06smtp03.uk.ibm.com (e06smtp03.uk.ibm.com [195.75.94.99]) by mx0a-001b2d01.pphosted.com with ESMTP id 2yua3xhky1-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Fri, 20 Mar 2020 10:44:03 -0400 Received: from localhost by e06smtp03.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Fri, 20 Mar 2020 14:43:57 -0000 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06avi18626390.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 02KEgtuA40829372 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 20 Mar 2020 14:42:55 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D29F8AE05A; Fri, 20 Mar 2020 14:43:56 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 76BAEAE051; Fri, 20 Mar 2020 14:43:56 +0000 (GMT) Received: from pomme.local (unknown [9.145.63.10]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Fri, 20 Mar 2020 14:43:56 +0000 (GMT) Subject: Re: [PATCH 1/2] KVM: PPC: Book3S HV: check caller of H_SVM_* Hcalls To: Greg Kurz References: <20200320102643.15516-1-ldufour@linux.ibm.com> <20200320102643.15516-2-ldufour@linux.ibm.com> <20200320132248.44b81b3b@bahia.lan> From: Laurent Dufour Date: Fri, 20 Mar 2020 15:43:54 +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: <20200320132248.44b81b3b@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: 20032014-0012-0000-0000-00000394869C X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 20032014-0013-0000-0000-000021D17040 Message-Id: <2268d1e3-3020-91c4-90e2-d2eced6a214a@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138, 18.0.645 definitions=2020-03-20_04:2020-03-20, 2020-03-20 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 spamscore=0 phishscore=0 priorityscore=1501 clxscore=1015 impostorscore=0 adultscore=0 malwarescore=0 bulkscore=0 mlxscore=0 mlxlogscore=999 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2003200059 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-kernel@vger.kernel.org, kvm-ppc@vger.kernel.org, Bharata B Rao , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Le 20/03/2020 à 13:22, Greg Kurz a écrit : > 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) ? If it doesn't, a malicious SVM would be able to call UV reserved Hcall like H_SVM_INIT_ABORT, etc... which is not a good idea. > > Shouldn't we also check the HV bit of the calling MSR as well to > disambiguate SVM and UV ? That's another way to do so, but since the SVM Hcall are going through the UV, it seems the right place (the UV) to do the filtering. >> >> Cc: Bharata B Rao >> Cc: Paul Mackerras >> Cc: Benjamin Herrenschmidt >> Cc: Michael Ellerman >> Signed-off-by: Laurent Dufour >> --- >> arch/powerpc/kvm/book3s_hv.c | 32 +++++++++++++++++++++----------- >> 1 file changed, 21 insertions(+), 11 deletions(-) >> >> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c >> index 33be4d93248a..43773182a737 100644 >> --- a/arch/powerpc/kvm/book3s_hv.c >> +++ b/arch/powerpc/kvm/book3s_hv.c >> @@ -1074,25 +1074,35 @@ int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu) >> kvmppc_get_gpr(vcpu, 6)); >> break; >> case H_SVM_PAGE_IN: >> - ret = kvmppc_h_svm_page_in(vcpu->kvm, >> - kvmppc_get_gpr(vcpu, 4), >> - kvmppc_get_gpr(vcpu, 5), >> - kvmppc_get_gpr(vcpu, 6)); >> + ret = H_UNSUPPORTED; >> + if (kvmppc_get_srr1(vcpu) & MSR_S) >> + ret = kvmppc_h_svm_page_in(vcpu->kvm, >> + kvmppc_get_gpr(vcpu, 4), >> + kvmppc_get_gpr(vcpu, 5), >> + kvmppc_get_gpr(vcpu, 6)); > > If calling kvmppc_h_svm_page_in() produces a "weird result" when > the MSR_S bit isn't set, then I think it should do the checking > itself, ie. pass vcpu. > > This would also prevent adding that many lines in kvmppc_pseries_do_hcall() > which is a big enough function already. The checking could be done in a > helper in book3s_hv_uvmem.c and used by all UV specific hcalls. I'm not convinced that would be better, and I followed the way checks for other Hcalls has been made (see H_TLB_INVALIDATE,..). I agree kvmppc_pseries_do_hcall() is long but this is just a big switch(), quite linear. > >> break; >> case H_SVM_PAGE_OUT: >> - ret = kvmppc_h_svm_page_out(vcpu->kvm, >> - kvmppc_get_gpr(vcpu, 4), >> - kvmppc_get_gpr(vcpu, 5), >> - kvmppc_get_gpr(vcpu, 6)); >> + ret = H_UNSUPPORTED; >> + if (kvmppc_get_srr1(vcpu) & MSR_S) >> + ret = kvmppc_h_svm_page_out(vcpu->kvm, >> + kvmppc_get_gpr(vcpu, 4), >> + kvmppc_get_gpr(vcpu, 5), >> + kvmppc_get_gpr(vcpu, 6)); >> break; >> case H_SVM_INIT_START: >> - ret = kvmppc_h_svm_init_start(vcpu->kvm); >> + ret = H_UNSUPPORTED; >> + if (kvmppc_get_srr1(vcpu) & MSR_S) >> + ret = kvmppc_h_svm_init_start(vcpu->kvm); >> break; >> case H_SVM_INIT_DONE: >> - ret = kvmppc_h_svm_init_done(vcpu->kvm); >> + ret = H_UNSUPPORTED; >> + if (kvmppc_get_srr1(vcpu) & MSR_S) >> + ret = kvmppc_h_svm_init_done(vcpu->kvm); >> break; >> case H_SVM_INIT_ABORT: >> - ret = kvmppc_h_svm_init_abort(vcpu->kvm); >> + ret = H_UNSUPPORTED; >> + if (kvmppc_get_srr1(vcpu) & MSR_S) >> + ret = kvmppc_h_svm_init_abort(vcpu->kvm); >> break; >> >> default: >