From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received-SPF: Pass (sender SPF authorized) identity=mailfrom; client-ip=134.134.136.24; helo=mga09.intel.com; envelope-from=star.zeng@intel.com; receiver=edk2-devel@lists.01.org Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) (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 B7ABC2115C317 for ; Fri, 28 Sep 2018 23:11:35 -0700 (PDT) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 28 Sep 2018 23:11:34 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,318,1534834800"; d="scan'208";a="94512988" Received: from fmsmsx106.amr.corp.intel.com ([10.18.124.204]) by fmsmga001.fm.intel.com with ESMTP; 28 Sep 2018 23:11:26 -0700 Received: from fmsmsx123.amr.corp.intel.com (10.18.125.38) by FMSMSX106.amr.corp.intel.com (10.18.124.204) with Microsoft SMTP Server (TLS) id 14.3.319.2; Fri, 28 Sep 2018 23:11:26 -0700 Received: from shsmsx101.ccr.corp.intel.com (10.239.4.153) by fmsmsx123.amr.corp.intel.com (10.18.125.38) with Microsoft SMTP Server (TLS) id 14.3.319.2; Fri, 28 Sep 2018 23:11:26 -0700 Received: from shsmsx102.ccr.corp.intel.com ([169.254.2.140]) by SHSMSX101.ccr.corp.intel.com ([169.254.1.220]) with mapi id 14.03.0319.002; Sat, 29 Sep 2018 14:11:23 +0800 From: "Zeng, Star" To: "Wu, Hao A" , "edk2-devel@lists.01.org" CC: "Yao, Jiewen" , "Zeng, Star" Thread-Topic: [PATCH v2 2/5] MdeModulePkg/FaultTolerantWrite:[CVE-2017-5753]Fix bounds check bypass Thread-Index: AQHUVJbXhTNuuCJOcUuh/zTrTRjGcKUGzSKA Date: Sat, 29 Sep 2018 06:11:23 +0000 Message-ID: <0C09AFA07DD0434D9E2A0C6AEB0483103BBF5E78@shsmsx102.ccr.corp.intel.com> References: <20180925061259.31680-1-hao.a.wu@intel.com> <20180925061259.31680-3-hao.a.wu@intel.com> In-Reply-To: <20180925061259.31680-3-hao.a.wu@intel.com> Accept-Language: zh-CN, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.239.127.40] MIME-Version: 1.0 Subject: Re: [PATCH v2 2/5] MdeModulePkg/FaultTolerantWrite:[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: Sat, 29 Sep 2018 06:11:35 -0000 Content-Language: en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Please double check whether the AsmLfence calling should be before the line= below. PrivateData =3D (VOID *)&SmmFtwWriteHeader->Data[Length]; Thanks, Star -----Original Message----- From: Wu, Hao A=20 Sent: Tuesday, September 25, 2018 2:13 PM To: edk2-devel@lists.01.org Cc: Wu, Hao A ; Yao, Jiewen ; Zen= g, Star Subject: [PATCH v2 2/5] MdeModulePkg/FaultTolerantWrite:[CVE-2017-5753]Fix = bounds check bypass REF:https://bugzilla.tianocore.org/show_bug.cgi?id=3D1194 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 mi= ght leave hints such as which memory locations have been brought into cache= . Malicious actors can use the bounds check bypass method (code gadgets wit= h controlled external inputs) to infer data values that have been used in s= peculative operations to reveal secrets which should not otherwise be acces= sed. This commit will focus on the SMI handler(s) registered within the FaultTol= erantWriteDxe driver and insert AsmLfence API to mitigate the bounds check = bypass issue. For SMI handler SmmFaultTolerantWriteHandler(): Under "case FTW_FUNCTION_WRITE:", 'SmmFtwWriteHeader->Length' can be a pote= ntial cross boundary access of the 'CommBuffer' (controlled external inputs) during speculative execution. This cross boundary access is later p= assed as parameter 'Length' into function FtwWrite(). Within function FtwWrite(), the value of 'Length' can be inferred by code: "CopyMem (MyBuffer + Offset, Buffer, Length);". One can observe which part = of the content within 'Buffer' was brought into cache to possibly reveal th= e value of 'Length'. Hence, this commit adds a AsmLfence() after the boundary/range checks of 'C= ommBuffer' to prevent the speculative execution. A more detailed explanation of the purpose of commit is under the 'Bounds c= heck bypass mitigation' section of the below link: https://software.intel.com/security-software-guidance/insights/host-firmwar= e-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: Jiewen Yao Cc: Star Zeng Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Hao Wu --- MdeModulePkg/Universal/FaultTolerantWriteDxe/FaultTolerantWriteSmm.c | 7= +++++++ MdeModulePkg/Universal/FaultTolerantWriteDxe/FaultTolerantWriteSmm.inf | 1= + 2 files changed, 8 insertions(+) diff --git a/MdeModulePkg/Universal/FaultTolerantWriteDxe/FaultTolerantWrit= eSmm.c b/MdeModulePkg/Universal/FaultTolerantWriteDxe/FaultTolerantWriteSmm= .c index 632313f076..27fcab19b6 100644 --- a/MdeModulePkg/Universal/FaultTolerantWriteDxe/FaultTolerantWriteSmm.c +++ b/MdeModulePkg/Universal/FaultTolerantWriteDxe/FaultTolerantWriteSmm +++ .c @@ -57,6 +57,7 @@ WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER= EXPRESS OR IMPLIED. #include #include #include +#include #include #include "FaultTolerantWrite.h" #include "FaultTolerantWriteSmmCommon.h" @@ -417,6 +418,12 @@ SmmFaultTolerantWriteHandler ( &SmmFvbHandle ); if (!EFI_ERROR (Status)) { + // + // The AsmLfence() call here is to ensure the previous range/conte= nt + // checks for the CommBuffer have been completed before calling in= to + // FtwWrite(). + // + AsmLfence (); Status =3D FtwWrite( &mFtwDevice->FtwInstance, SmmFtwWriteHeader->Lba, diff --git a/MdeModulePkg/Unive= rsal/FaultTolerantWriteDxe/FaultTolerantWriteSmm.inf b/MdeModulePkg/Univers= al/FaultTolerantWriteDxe/FaultTolerantWriteSmm.inf index 85d109e8d9..606cc2266b 100644 --- a/MdeModulePkg/Universal/FaultTolerantWriteDxe/FaultTolerantWriteSmm.in= f +++ b/MdeModulePkg/Universal/FaultTolerantWriteDxe/FaultTolerantWriteSmm +++ .inf @@ -55,6 +55,7 @@ PcdLib ReportStatusCodeLib SmmMemLib + BaseLib =20 [Guids] # -- 2.12.0.windows.1