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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 26ADCC4332F for ; Wed, 3 Nov 2021 14:06:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 129E76113E for ; Wed, 3 Nov 2021 14:06:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232237AbhKCOJT (ORCPT ); Wed, 3 Nov 2021 10:09:19 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:58118 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231955AbhKCOJH (ORCPT ); Wed, 3 Nov 2021 10:09:07 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1635948390; 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=TfPrvtwM19WIN0IdRHpwKBi+MFW2ozo1SwSCyDq526E=; b=fvPQ4c5NrF5tMUf2xV8bLzX9lOKwHWoXruVySNMNE1tEFH17eqR5365OZqLmDbVE54awkM 2PnKcEr2apZ9B8MBVa7jgua9PFVUHhzeVL2aiRrIKa6iv3NMXkcuLrC+EBmJ9U/VN2QjhZ zl1tXc1w3WtXkcn2/kGdc/zReEg0VGQ= 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-363-hrMdwZBDOsCY3P2RknSiZw-1; Wed, 03 Nov 2021 10:06:27 -0400 X-MC-Unique: hrMdwZBDOsCY3P2RknSiZw-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id EDDAF80668E; Wed, 3 Nov 2021 14:06:24 +0000 (UTC) Received: from virtlab701.virt.lab.eng.bos.redhat.com (virtlab701.virt.lab.eng.bos.redhat.com [10.19.152.228]) by smtp.corp.redhat.com (Postfix) with ESMTP id E04AB100EA05; Wed, 3 Nov 2021 14:06:23 +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: [PATCH v5 5/7] nSVM: use svm->nested.save to load vmcb12 registers and avoid TOC/TOU races Date: Wed, 3 Nov 2021 10:05:25 -0400 Message-Id: <20211103140527.752797-6-eesposit@redhat.com> In-Reply-To: <20211103140527.752797-1-eesposit@redhat.com> References: <20211103140527.752797-1-eesposit@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Use the already checked svm->nested.save cached fields (EFER, CR0, CR4, ...) instead of vmcb12's in nested_vmcb02_prepare_save(). This prevents from creating TOC/TOU races, since the guest could modify the vmcb12 fields. This also avoids the need of force-setting EFER_SVME in nested_vmcb02_prepare_save. Signed-off-by: Emanuele Giuseppe Esposito Reviewed-by: Maxim Levitsky --- arch/x86/kvm/svm/nested.c | 24 ++++++------------------ 1 file changed, 6 insertions(+), 18 deletions(-) diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index 64fb43234e06..cdddd3258ddf 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -248,13 +248,6 @@ static bool nested_vmcb_check_controls(struct kvm_vcpu *vcpu, static bool _nested_vmcb_check_save(struct kvm_vcpu *vcpu, struct vmcb_save_area_cached *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; @@ -511,15 +504,10 @@ 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; @@ -534,8 +522,8 @@ static void nested_vmcb02_prepare_save(struct vcpu_svm *svm, struct vmcb *vmcb12 /* These bits will be set properly on the first execution when new_vmc12 is true */ if (unlikely(new_vmcb12 || vmcb_is_dirty(vmcb12, VMCB_DR))) { - svm->vmcb->save.dr7 = vmcb12->save.dr7 | DR7_FIXED_1; - svm->vcpu.arch.dr6 = vmcb12->save.dr6 | DR6_ACTIVE_LOW; + svm->vmcb->save.dr7 = svm->nested.save.dr7 | DR7_FIXED_1; + svm->vcpu.arch.dr6 = svm->nested.save.dr6 | DR6_ACTIVE_LOW; vmcb_mark_dirty(svm->vmcb, VMCB_DR); } } @@ -649,7 +637,7 @@ int enter_svm_guest_mode(struct kvm_vcpu *vcpu, u64 vmcb12_gpa, nested_vmcb02_prepare_control(svm); nested_vmcb02_prepare_save(svm, vmcb12); - ret = nested_svm_load_cr3(&svm->vcpu, vmcb12->save.cr3, + ret = nested_svm_load_cr3(&svm->vcpu, svm->nested.save.cr3, nested_npt_enabled(svm), from_vmrun); if (ret) return ret; -- 2.27.0