From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received-SPF: Pass (sender SPF authorized) identity=mailfrom; client-ip=134.134.136.65; helo=mga03.intel.com; envelope-from=hao.a.wu@intel.com; receiver=edk2-devel@lists.01.org Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) (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 6B4A42115C093 for ; Fri, 28 Sep 2018 23:57:44 -0700 (PDT) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 28 Sep 2018 23:57:43 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,318,1534834800"; d="scan'208";a="94950121" Received: from shwdeopenpsi014.ccr.corp.intel.com ([10.239.9.19]) by orsmga001.jf.intel.com with ESMTP; 28 Sep 2018 23:57:40 -0700 From: Hao Wu To: edk2-devel@lists.01.org Cc: Hao Wu Date: Sat, 29 Sep 2018 14:57:33 +0800 Message-Id: <20180929065736.12796-3-hao.a.wu@intel.com> X-Mailer: git-send-email 2.12.0.windows.1 In-Reply-To: <20180929065736.12796-1-hao.a.wu@intel.com> References: <20180929065736.12796-1-hao.a.wu@intel.com> Subject: [PATCH v3 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 06:57:44 -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. This commit will focus on the SMI handler(s) registered within the FaultTolerantWriteDxe 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 potential cross boundary access of the 'CommBuffer' (controlled external inputs) during speculative execution. This cross boundary access is later passed 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 the value of 'Length'. Hence, this commit adds a AsmLfence() after the boundary/range checks of 'CommBuffer' 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 Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Hao Wu Reviewed-by: Jiewen Yao Reviewed-by: Star Zeng --- MdeModulePkg/Universal/FaultTolerantWriteDxe/FaultTolerantWriteSmm.c | 7 +++++++ MdeModulePkg/Universal/FaultTolerantWriteDxe/FaultTolerantWriteSmm.inf | 1 + 2 files changed, 8 insertions(+) diff --git a/MdeModulePkg/Universal/FaultTolerantWriteDxe/FaultTolerantWriteSmm.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/content + // checks for the CommBuffer have been completed before calling into + // FtwWrite(). + // + AsmLfence (); Status = FtwWrite( &mFtwDevice->FtwInstance, SmmFtwWriteHeader->Lba, diff --git a/MdeModulePkg/Universal/FaultTolerantWriteDxe/FaultTolerantWriteSmm.inf b/MdeModulePkg/Universal/FaultTolerantWriteDxe/FaultTolerantWriteSmm.inf index 85d109e8d9..606cc2266b 100644 --- a/MdeModulePkg/Universal/FaultTolerantWriteDxe/FaultTolerantWriteSmm.inf +++ b/MdeModulePkg/Universal/FaultTolerantWriteDxe/FaultTolerantWriteSmm.inf @@ -55,6 +55,7 @@ PcdLib ReportStatusCodeLib SmmMemLib + BaseLib [Guids] # -- 2.12.0.windows.1