From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received-SPF: Pass (sender SPF authorized) identity=mailfrom; client-ip=192.55.52.115; helo=mga14.intel.com; envelope-from=hao.a.wu@intel.com; receiver=edk2-devel@lists.01.org Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id B8840210FC38B for ; Wed, 19 Sep 2018 23:41:16 -0700 (PDT) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 19 Sep 2018 23:41:16 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.53,397,1531810800"; d="scan'208";a="234436663" Received: from shwdeopenpsi014.ccr.corp.intel.com ([10.239.9.19]) by orsmga004.jf.intel.com with ESMTP; 19 Sep 2018 23:41:15 -0700 From: Hao Wu To: edk2-devel@lists.01.org Cc: Hao Wu , Laszlo Ersek , Jiewen Yao , Michael D Kinney , Eric Dong Date: Thu, 20 Sep 2018 14:41:03 +0800 Message-Id: <20180920064103.14600-6-hao.a.wu@intel.com> X-Mailer: git-send-email 2.12.0.windows.1 In-Reply-To: <20180920064103.14600-1-hao.a.wu@intel.com> References: <20180920064103.14600-1-hao.a.wu@intel.com> Subject: [PATCH v1 5/5] UefiCpuPkg/PiSmmCpuDxeSmm: [CVE-2017-5753] Fix bounds check bypass X-BeenThere: edk2-devel@lists.01.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: EDK II Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 20 Sep 2018 06:41:16 -0000 REF:https://bugzilla.tianocore.org/show_bug.cgi?id=1194 Speculative execution is used by processor to avoid having to wait for data to arrive from memory, or for previous operations to finish, the processor may speculate as to what will be executed. If the speculation is incorrect, the speculatively executed instructions might leave hints such as which memory locations have been brought into cache. Malicious actors can use the bounds check bypass method (code gadgets with controlled external inputs) to infer data values that have been used in speculative operations to reveal secrets which should not otherwise be accessed. It is possible for SMI handler(s) to call EFI_SMM_CPU_PROTOCOL service ReadSaveState() and use the content in the 'CommBuffer' (controlled external inputs) as the 'CpuIndex'. So this commit will insert LoadFence API to mitigate the bounds check bypass issue within SmmReadSaveState(). For SmmReadSaveState(): The 'CpuIndex' will be passed into function ReadSaveStateRegister(). And then in to ReadSaveStateRegisterByIndex(). With the call: ReadSaveStateRegisterByIndex ( CpuIndex, SMM_SAVE_STATE_REGISTER_IOMISC_INDEX, sizeof(IoMisc.Uint32), &IoMisc.Uint32 ); The 'IoMisc' can be a cross boundary access during speculative execution. Later, 'IoMisc' is used as the index to access buffers 'mSmmCpuIoWidth' and 'mSmmCpuIoType'. One can observe which part of the content within those buffers was brought into cache to possibly reveal the value of 'IoMisc'. Hence, this commit adds a LoadFence after the check of 'CpuIndex' within function SmmReadSaveState() to prevent the speculative execution. A more detailed explanation of the purpose of commit is under the 'Bounds check bypass mitigation' section of the below link: https://software.intel.com/security-software-guidance/insights/host-firmware-speculative-execution-side-channel-mitigation And the document at: https://software.intel.com/security-software-guidance/api-app/sites/default/files/337879-analyzing-potential-bounds-Check-bypass-vulnerabilities.pdf Cc: Laszlo Ersek Cc: Jiewen Yao Cc: Michael D Kinney Cc: Eric Dong Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Hao Wu --- UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c | 1 + 1 file changed, 1 insertion(+) diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c index fbf74e8d90..256a8bbb94 100644 --- a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c @@ -237,6 +237,7 @@ SmmReadSaveState ( if ((CpuIndex >= gSmst->NumberOfCpus) || (Buffer == NULL)) { return EFI_INVALID_PARAMETER; } + LoadFence (); // // Check for special EFI_SMM_SAVE_STATE_REGISTER_PROCESSOR_ID -- 2.12.0.windows.1