From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752028AbeBAKGF (ORCPT ); Thu, 1 Feb 2018 05:06:05 -0500 Received: from terminus.zytor.com ([65.50.211.136]:59023 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751712AbeBAKGE (ORCPT ); Thu, 1 Feb 2018 05:06:04 -0500 Date: Thu, 1 Feb 2018 02:03:50 -0800 From: tip-bot for Dan Williams Message-ID: Cc: ahonig@google.com, mingo@kernel.org, jmattson@google.com, pbonzini@redhat.com, linux-kernel@vger.kernel.org, hpa@zytor.com, dan.j.williams@intel.com, tglx@linutronix.de Reply-To: ahonig@google.com, mingo@kernel.org, jmattson@google.com, pbonzini@redhat.com, linux-kernel@vger.kernel.org, tglx@linutronix.de, dan.j.williams@intel.com, hpa@zytor.com In-Reply-To: <151744959670.6342.3001723920950249067.stgit@dwillia2-desk3.amr.corp.intel.com> References: <151744959670.6342.3001723920950249067.stgit@dwillia2-desk3.amr.corp.intel.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/pti] x86/kvm: Update spectre-v1 mitigation Git-Commit-ID: 085331dfc6bbe3501fb936e657331ca943827600 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 085331dfc6bbe3501fb936e657331ca943827600 Gitweb: https://git.kernel.org/tip/085331dfc6bbe3501fb936e657331ca943827600 Author: Dan Williams AuthorDate: Wed, 31 Jan 2018 17:47:03 -0800 Committer: Thomas Gleixner CommitDate: Thu, 1 Feb 2018 10:59:10 +0100 x86/kvm: Update spectre-v1 mitigation Commit 75f139aaf896 "KVM: x86: Add memory barrier on vmcs field lookup" added a raw 'asm("lfence");' to prevent a bounds check bypass of 'vmcs_field_to_offset_table'. The lfence can be avoided in this path by using the array_index_nospec() helper designed for these types of fixes. Signed-off-by: Dan Williams Signed-off-by: Thomas Gleixner Acked-by: Paolo Bonzini Cc: Andrew Honig Cc: kvm@vger.kernel.org Cc: Jim Mattson Link: https://lkml.kernel.org/r/151744959670.6342.3001723920950249067.stgit@dwillia2-desk3.amr.corp.intel.com --- arch/x86/kvm/vmx.c | 20 +++++++++----------- 1 file changed, 9 insertions(+), 11 deletions(-) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index a8b96dc..2894282 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -34,6 +34,7 @@ #include #include #include +#include #include "kvm_cache_regs.h" #include "x86.h" @@ -898,21 +899,18 @@ static const unsigned short vmcs_field_to_offset_table[] = { static inline short vmcs_field_to_offset(unsigned long field) { - BUILD_BUG_ON(ARRAY_SIZE(vmcs_field_to_offset_table) > SHRT_MAX); + const size_t size = ARRAY_SIZE(vmcs_field_to_offset_table); + unsigned short offset; - if (field >= ARRAY_SIZE(vmcs_field_to_offset_table)) + BUILD_BUG_ON(size > SHRT_MAX); + if (field >= size) return -ENOENT; - /* - * FIXME: Mitigation for CVE-2017-5753. To be replaced with a - * generic mechanism. - */ - asm("lfence"); - - if (vmcs_field_to_offset_table[field] == 0) + field = array_index_nospec(field, size); + offset = vmcs_field_to_offset_table[field]; + if (offset == 0) return -ENOENT; - - return vmcs_field_to_offset_table[field]; + return offset; } static inline struct vmcs12 *get_vmcs12(struct kvm_vcpu *vcpu)