From patchwork Tue Jan 30 01:03:10 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dan Williams X-Patchwork-Id: 10191257 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 222FD60375 for ; Tue, 30 Jan 2018 01:13:29 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 150F028492 for ; Tue, 30 Jan 2018 01:13:29 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 0982128533; Tue, 30 Jan 2018 01:13:29 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=2.0 tests=BAYES_00, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.wl.linuxfoundation.org (Postfix) with SMTP id 11D4B28492 for ; Tue, 30 Jan 2018 01:13:27 +0000 (UTC) Received: (qmail 32721 invoked by uid 550); 30 Jan 2018 01:12:25 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 32651 invoked from network); 30 Jan 2018 01:12:24 -0000 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.46,433,1511856000"; d="scan'208";a="199804180" Subject: [PATCH v6 11/13] kvm, x86: update spectre-v1 mitigation From: Dan Williams To: tglx@linutronix.de, mingo@kernel.org Cc: linux-arch@vger.kernel.org, kernel-hardening@lists.openwall.com, Andrew Honig , linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org, Paolo Bonzini , alan@linux.intel.com, torvalds@linux-foundation.org, Jim Mattson Date: Mon, 29 Jan 2018 17:03:10 -0800 Message-ID: <151727419015.33451.13762926723789552997.stgit@dwillia2-desk3.amr.corp.intel.com> In-Reply-To: <151727412964.33451.17213780323040673404.stgit@dwillia2-desk3.amr.corp.intel.com> References: <151727412964.33451.17213780323040673404.stgit@dwillia2-desk3.amr.corp.intel.com> User-Agent: StGit/0.17.1-9-g687f MIME-Version: 1.0 X-Virus-Scanned: ClamAV using ClamSMTP 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'. We can save an lfence in this path and just use the common array_index_nospec() helper designed for these types of fixes. Cc: Andrew Honig Cc: Jim Mattson Acked-by: Paolo Bonzini Signed-off-by: Dan Williams --- arch/x86/kvm/vmx.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 924589c53422..8514186241d2 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" @@ -883,13 +884,18 @@ 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) || - vmcs_field_to_offset_table[field] == 0) + BUILD_BUG_ON(size > SHRT_MAX); + if (field >= size) return -ENOENT; - return vmcs_field_to_offset_table[field]; + field = array_index_nospec(field, size); + offset = vmcs_field_to_offset_table[field]; + if (offset == 0) + return -ENOENT; + return offset; } static inline struct vmcs12 *get_vmcs12(struct kvm_vcpu *vcpu)