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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 8B70FC77B75 for ; Mon, 8 May 2023 21:12:19 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pw89G-0002Io-Hu; Mon, 08 May 2023 17:11:59 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pw89E-0002IW-M2 for qemu-devel@nongnu.org; Mon, 08 May 2023 17:11:56 -0400 Received: from mail-pl1-f180.google.com ([209.85.214.180]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1pw89C-0005bI-Mw for qemu-devel@nongnu.org; Mon, 08 May 2023 17:11:56 -0400 Received: by mail-pl1-f180.google.com with SMTP id d9443c01a7336-1ab032d9266so47606625ad.0 for ; Mon, 08 May 2023 14:11:52 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1683580311; x=1686172311; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=NFnNeAlUj9C+huN2rBEcxkVDG8OipZYXhgLegmZBDMk=; b=LFgCbcbih8jGfV0QDwxHBFY3U5eo6NcUUAx0fi5+LonPQEm8/W6XENEYhLhnAF7hsA HABo1Dqxq9sBQighLBRYAlN1uPx2E1Js3SWOAQGMC2zffYHQJjKaXd4sMjK4upGijh77 ZRs8jhHUY8TmOkWDDYi1WUSjy7jsLIHKLwrrkmYVojBDLPLm8T/Yx8lM0wYwj2ukXlR1 8qG+a8qJqwrOCloXyot1nDeG96ekWat7g6GfAkGOW6y87pCCLUpwU+Wh15F6mtaeB4UJ vyuYOrM9dK6JbbqsT3ITvtcyf7jVEqQ6m9U9LqWrfD+C3yarDMY1nCXUYeitn55WGysX obtw== X-Gm-Message-State: AC+VfDz0vb1tsJDePnxUqsRu/F1IBh1ajjvryOWTk+ZpR4XCQrEp6Mxy mDjexdHQwquaRZSSTpa9wf8= X-Google-Smtp-Source: ACHHUZ6BtFvSoF+wcEO4loE9NZdFfCT+I/PFTdAZhqBSeRBB8gma6+CJUbrsA8zRjfVrnuCD3KU/Lw== X-Received: by 2002:a17:90a:65cb:b0:248:8399:1f7c with SMTP id i11-20020a17090a65cb00b0024883991f7cmr11239406pjs.38.1683580310757; Mon, 08 May 2023 14:11:50 -0700 (PDT) Received: from liuwe-devbox-debian-v2 ([20.69.120.36]) by smtp.gmail.com with ESMTPSA id k14-20020a170902760e00b0019aeddce6casm7648553pll.205.2023.05.08.14.11.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 08 May 2023 14:11:50 -0700 (PDT) Date: Mon, 8 May 2023 21:11:48 +0000 From: Wei Liu To: =?iso-8859-1?Q?Micka=EBl_Sala=FCn?= Cc: Borislav Petkov , Dave Hansen , "H . Peter Anvin" , Ingo Molnar , Kees Cook , Paolo Bonzini , Sean Christopherson , Thomas Gleixner , Vitaly Kuznetsov , Wanpeng Li , Alexander Graf , Forrest Yuan Yu , James Morris , John Andersen , Liran Alon , "Madhavan T . Venkataraman" , Marian Rotariu , Mihai =?utf-8?B?RG9uyJt1?= , =?utf-8?B?TmljdciZb3IgQ8OuyJt1?= , Rick Edgecombe , Thara Gopinath , Will Deacon , Zahra Tarkhani , =?utf-8?Q?=C8=98tefan_=C8=98icleru?= , dev@lists.cloudhypervisor.org, kvm@vger.kernel.org, linux-hardening@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org, x86@kernel.org, xen-devel@lists.xenproject.org, Wei Liu Subject: Re: [PATCH v1 5/9] KVM: x86: Add new hypercall to lock control registers Message-ID: References: <20230505152046.6575-1-mic@digikod.net> <20230505152046.6575-6-mic@digikod.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20230505152046.6575-6-mic@digikod.net> Received-SPF: pass client-ip=209.85.214.180; envelope-from=wei.liu.linux@gmail.com; helo=mail-pl1-f180.google.com X-Spam_score_int: -13 X-Spam_score: -1.4 X-Spam_bar: - X-Spam_report: (-1.4 / 5.0 requ) BAYES_00=-1.9, FREEMAIL_FORGED_FROMDOMAIN=0.249, FREEMAIL_FROM=0.001, HEADER_FROM_DIFFERENT_DOMAINS=0.25, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Fri, May 05, 2023 at 05:20:42PM +0200, Mickaël Salaün wrote: > This enables guests to lock their CR0 and CR4 registers with a subset of > X86_CR0_WP, X86_CR4_SMEP, X86_CR4_SMAP, X86_CR4_UMIP, X86_CR4_FSGSBASE > and X86_CR4_CET flags. > > The new KVM_HC_LOCK_CR_UPDATE hypercall takes two arguments. The first > is to identify the control register, and the second is a bit mask to > pin (i.e. mark as read-only). > > These register flags should already be pinned by Linux guests, but once > compromised, this self-protection mechanism could be disabled, which is > not the case with this dedicated hypercall. > > Cc: Borislav Petkov > Cc: Dave Hansen > Cc: H. Peter Anvin > Cc: Ingo Molnar > Cc: Kees Cook > Cc: Madhavan T. Venkataraman > Cc: Paolo Bonzini > Cc: Sean Christopherson > Cc: Thomas Gleixner > Cc: Vitaly Kuznetsov > Cc: Wanpeng Li > Signed-off-by: Mickaël Salaün > Link: https://lore.kernel.org/r/20230505152046.6575-6-mic@digikod.net [...] > hw_cr4 = (cr4_read_shadow() & X86_CR4_MCE) | (cr4 & ~X86_CR4_MCE); > if (is_unrestricted_guest(vcpu)) > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index ffab64d08de3..a529455359ac 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -7927,11 +7927,77 @@ static unsigned long emulator_get_cr(struct x86_emulate_ctxt *ctxt, int cr) > return value; > } > > +#ifdef CONFIG_HEKI > + > +extern unsigned long cr4_pinned_mask; > + Can this be moved to a header file? > +static int heki_lock_cr(struct kvm *const kvm, const unsigned long cr, > + unsigned long pin) > +{ > + if (!pin) > + return -KVM_EINVAL; > + > + switch (cr) { > + case 0: > + /* Cf. arch/x86/kernel/cpu/common.c */ > + if (!(pin & X86_CR0_WP)) > + return -KVM_EINVAL; > + > + if ((read_cr0() & pin) != pin) > + return -KVM_EINVAL; > + > + atomic_long_or(pin, &kvm->heki_pinned_cr0); > + return 0; > + case 4: > + /* Checks for irrelevant bits. */ > + if ((pin & cr4_pinned_mask) != pin) > + return -KVM_EINVAL; > + It is enforcing the host mask on the guest, right? If the guest's set is a super set of the host's then it will get rejected. > + /* Ignores bits not present in host. */ > + pin &= __read_cr4(); > + atomic_long_or(pin, &kvm->heki_pinned_cr4); > + return 0; > + } > + return -KVM_EINVAL; > +} > + > +int heki_check_cr(const struct kvm *const kvm, const unsigned long cr, > + const unsigned long val) > +{ > + unsigned long pinned; > + > + switch (cr) { > + case 0: > + pinned = atomic_long_read(&kvm->heki_pinned_cr0); > + if ((val & pinned) != pinned) { > + pr_warn_ratelimited( > + "heki-kvm: Blocked CR0 update: 0x%lx\n", val); I think if the message contains the VM and VCPU identifier it will become more useful. Thanks, Wei.