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 X-Spam-Level: X-Spam-Status: No, score=-8.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, HK_RANDOM_FROM,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 C29A0C2BB1D for ; Sun, 15 Mar 2020 05:23:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A583520722 for ; Sun, 15 Mar 2020 05:23:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727662AbgCOFXM (ORCPT ); Sun, 15 Mar 2020 01:23:12 -0400 Received: from mga18.intel.com ([134.134.136.126]:47872 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727584AbgCOFXK (ORCPT ); Sun, 15 Mar 2020 01:23:10 -0400 IronPort-SDR: M8wLh0PkbsrDMfXmxiC9M9v1o2qx55D7FNFQCRH61QtBpbjgZPXi22FDqFSBbbTx5oeaEJ8Ok/ Qc08hbZ1QZDA== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Mar 2020 22:23:10 -0700 IronPort-SDR: fKea1dvGBAMBVCZZshILki/T40YvFqjeQKMqXwGD1Ef9Ff69dkMLBhdMecbkabe/wMICLzMRy1 D1QlGtvoHpSA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,555,1574150400"; d="scan'208";a="267194251" Received: from lxy-clx-4s.sh.intel.com ([10.239.43.160]) by fmsmga004.fm.intel.com with ESMTP; 14 Mar 2020 22:23:06 -0700 From: Xiaoyao Li To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , hpa@zytor.com, Paolo Bonzini , Sean Christopherson , kvm@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org Cc: Andy Lutomirski , Peter Zijlstra , Arvind Sankar , Fenghua Yu , Tony Luck , Vitaly Kuznetsov , Jim Mattson , Xiaoyao Li Subject: [PATCH v5 5/9] kvm: x86: Emulate split-lock access as a write Date: Sun, 15 Mar 2020 13:05:13 +0800 Message-Id: <20200315050517.127446-6-xiaoyao.li@intel.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200315050517.127446-1-xiaoyao.li@intel.com> References: <20200315050517.127446-1-xiaoyao.li@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If split lock detect is on (warn/fatal), #AC handler calls die() when split lock happens in kernel. Malicous guest can exploit the KVM emulator to trigger split lock #AC in kernel[1]. So just emulating the access as a write if it's a split-lock access (the same as access spans page) to avoid malicious attacking kernel. More discussion can be found [2][3]. [1] https://lore.kernel.org/lkml/8c5b11c9-58df-38e7-a514-dc12d687b198@redhat.com/ [2] https://lkml.kernel.org/r/20200131200134.GD18946@linux.intel.com [3] https://lkml.kernel.org/r/20200227001117.GX9940@linux.intel.com Suggested-by: Sean Christopherson Signed-off-by: Xiaoyao Li --- arch/x86/include/asm/cpu.h | 2 ++ arch/x86/kernel/cpu/intel.c | 6 ++++++ arch/x86/kvm/x86.c | 7 ++++++- 3 files changed, 14 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h index ff567afa6ee1..d2071f6a35ac 100644 --- a/arch/x86/include/asm/cpu.h +++ b/arch/x86/include/asm/cpu.h @@ -44,6 +44,7 @@ unsigned int x86_stepping(unsigned int sig); extern void __init cpu_set_core_cap_bits(struct cpuinfo_x86 *c); extern void switch_to_sld(unsigned long tifn); extern bool handle_user_split_lock(unsigned long ip); +extern bool split_lock_detect_on(void); #else static inline void __init cpu_set_core_cap_bits(struct cpuinfo_x86 *c) {} static inline void switch_to_sld(unsigned long tifn) {} @@ -51,5 +52,6 @@ static inline bool handle_user_split_lock(unsigned long ip) { return false; } +static inline bool split_lock_detect_on(void) { return false; } #endif #endif /* _ASM_X86_CPU_H */ diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index c401d174c8db..de94957a11a4 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -1102,6 +1102,12 @@ static void split_lock_init(struct cpuinfo_x86 *c) sld_state = sld_disable; } +bool split_lock_detect_on(void) +{ + return sld_state == sld_warn || sld_state == sld_fatal; +} +EXPORT_SYMBOL_GPL(split_lock_detect_on); + bool handle_user_split_lock(unsigned long ip) { if (sld_state == sld_fatal) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 5de200663f51..1a0e6c0b1b39 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -5873,6 +5873,7 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt, { struct kvm_host_map map; struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt); + u64 page_line_mask = PAGE_MASK; gpa_t gpa; char *kaddr; bool exchanged; @@ -5887,7 +5888,11 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt, (gpa & PAGE_MASK) == APIC_DEFAULT_PHYS_BASE) goto emul_write; - if (((gpa + bytes - 1) & PAGE_MASK) != (gpa & PAGE_MASK)) + if (split_lock_detect_on()) + page_line_mask = ~(cache_line_size() - 1); + + /* when write spans page or spans cache when SLD enabled */ + if (((gpa + bytes - 1) & page_line_mask) != (gpa & page_line_mask)) goto emul_write; if (kvm_vcpu_map(vcpu, gpa_to_gfn(gpa), &map)) -- 2.20.1