From patchwork Fri Sep 3 10:20:39 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Emanuele Giuseppe Esposito X-Patchwork-Id: 12474085 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=-16.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 47B1DC433EF for ; Fri, 3 Sep 2021 10:21:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2EC3C60F42 for ; Fri, 3 Sep 2021 10:21:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1349141AbhICKWk (ORCPT ); Fri, 3 Sep 2021 06:22:40 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:26610 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1349112AbhICKWj (ORCPT ); Fri, 3 Sep 2021 06:22:39 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1630664499; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=FZd3jRLUUu1Oy1RGPc5d71idLDLNiXdx75BhhAmTkyE=; b=O0KIrlZxGyHNl8jiLacbfeX8VQY4h+/kGBTNRCh1K7fqjOfhsNPH0AcAwrF+VmpGSmiJBl uRtgu2zyAstxBsXx6AFFbX5DZTkQYZLZElMNJfOZToUEWPYyeOga89mEPHr92UgPRG3f/E HZrgVd3R4VwSAHN1EsNS5RQGmyaVWvE= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-150-FuHjKf-cNY6BIGXsNvaQRg-1; Fri, 03 Sep 2021 06:21:38 -0400 X-MC-Unique: FuHjKf-cNY6BIGXsNvaQRg-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7E591501E1; Fri, 3 Sep 2021 10:21:36 +0000 (UTC) Received: from localhost.localdomain (unknown [10.39.193.161]) by smtp.corp.redhat.com (Postfix) with ESMTP id DE2CF5D9C6; Fri, 3 Sep 2021 10:21:32 +0000 (UTC) From: Emanuele Giuseppe Esposito To: kvm@vger.kernel.org Cc: Paolo Bonzini , Maxim Levitsky , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , linux-kernel@vger.kernel.org, Emanuele Giuseppe Esposito Subject: [RFC PATCH 3/3] nSVM: use svm->nested.save to load vmcb12 registers and avoid TOC/TOU races Date: Fri, 3 Sep 2021 12:20:39 +0200 Message-Id: <20210903102039.55422-4-eesposit@redhat.com> In-Reply-To: <20210903102039.55422-1-eesposit@redhat.com> References: <20210903102039.55422-1-eesposit@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Move the checks done by nested_vmcb_valid_sregs and nested_vmcb_check_controls directly in enter_svm_guest_mode, and use svm->nested.save cached fields (EFER, CR0, CR4) instead of vmcb12's. This prevents from creating TOC/TOU races. This also avoids the need of force-setting EFER_SVME in nested_vmcb02_prepare_save. Signed-off-by: Emanuele Giuseppe Esposito --- arch/x86/kvm/svm/nested.c | 23 ++++++----------------- 1 file changed, 6 insertions(+), 17 deletions(-) diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index 2491c77203c7..487810cfefde 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -280,13 +280,6 @@ static bool nested_vmcb_check_controls(struct kvm_vcpu *vcpu, static bool nested_vmcb_valid_sregs(struct kvm_vcpu *vcpu, struct vmcb_save_area *save) { - /* - * FIXME: these should be done after copying the fields, - * to avoid TOC/TOU races. For these save area checks - * the possible damage is limited since kvm_set_cr0 and - * kvm_set_cr4 handle failure; EFER_SVME is an exception - * so it is force-set later in nested_prepare_vmcb_save. - */ if (CC(!(save->efer & EFER_SVME))) return false; @@ -459,7 +452,8 @@ void nested_vmcb02_compute_g_pat(struct vcpu_svm *svm) svm->nested.vmcb02.ptr->save.g_pat = svm->vmcb01.ptr->save.g_pat; } -static void nested_vmcb02_prepare_save(struct vcpu_svm *svm, struct vmcb *vmcb12) +static void nested_vmcb02_prepare_save(struct vcpu_svm *svm, + struct vmcb *vmcb12) { bool new_vmcb12 = false; @@ -488,15 +482,10 @@ static void nested_vmcb02_prepare_save(struct vcpu_svm *svm, struct vmcb *vmcb12 kvm_set_rflags(&svm->vcpu, vmcb12->save.rflags | X86_EFLAGS_FIXED); - /* - * Force-set EFER_SVME even though it is checked earlier on the - * VMCB12, because the guest can flip the bit between the check - * and now. Clearing EFER_SVME would call svm_free_nested. - */ - svm_set_efer(&svm->vcpu, vmcb12->save.efer | EFER_SVME); + svm_set_efer(&svm->vcpu, svm->nested.save.efer); - svm_set_cr0(&svm->vcpu, vmcb12->save.cr0); - svm_set_cr4(&svm->vcpu, vmcb12->save.cr4); + svm_set_cr0(&svm->vcpu, svm->nested.save.cr0); + svm_set_cr4(&svm->vcpu, svm->nested.save.cr4); svm->vcpu.arch.cr2 = vmcb12->save.cr2; @@ -671,7 +660,7 @@ int nested_svm_vmrun(struct kvm_vcpu *vcpu) nested_load_control_from_vmcb12(svm, &vmcb12->control); nested_load_save_from_vmcb12(svm, &vmcb12->save); - if (!nested_vmcb_valid_sregs(vcpu, &vmcb12->save) || + if (!nested_vmcb_valid_sregs(vcpu, &svm->nested.save) || !nested_vmcb_check_controls(vcpu, &svm->nested.ctl)) { vmcb12->control.exit_code = SVM_EXIT_ERR; vmcb12->control.exit_code_hi = 0;