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 TBD. 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 Cc: Star Zeng <[email protected]> Cc: Jiewen Yao <[email protected]> Cc: Laszlo Ersek <[email protected]> Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Hao Wu <[email protected]> --- MdeModulePkg/Library/SmmCorePerformanceLib/SmmCorePerformanceLib.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/MdeModulePkg/Library/SmmCorePerformanceLib/SmmCorePerformanceLib.c b/MdeModulePkg/Library/SmmCorePerformanceLib/SmmCorePerformanceLib.c index cd1f1a5d5f..63c1eea3a2 100644 --- a/MdeModulePkg/Library/SmmCorePerformanceLib/SmmCorePerformanceLib.c +++ b/MdeModulePkg/Library/SmmCorePerformanceLib/SmmCorePerformanceLib.c @@ -16,7 +16,7 @@ SmmPerformanceHandlerEx(), SmmPerformanceHandler() will receive untrusted input and do basic validation. -Copyright (c) 2011 - 2017, Intel Corporation. All rights reserved.<BR> +Copyright (c) 2011 - 2018, Intel Corporation. All rights reserved.<BR> This program and the accompanying materials are licensed and made available under the terms and conditions of the BSD License which accompanies this distribution. The full text of the license may be found at @@ -538,6 +538,13 @@ SmmPerformanceHandlerEx ( break; } + // + // The AsmLfence() call here is to ensure the previous range/content + // checks for the CommBuffer have been completed before calling + // CopyMem(). + // + AsmLfence (); + GaugeEntryExArray = (GAUGE_DATA_ENTRY_EX *) (mGaugeData + 1); for (Index = 0; Index < NumberOfEntries; Index++) { @@ -650,6 +657,13 @@ SmmPerformanceHandler ( break; } + // + // The AsmLfence() call here is to ensure the previous range/content + // checks for the CommBuffer have been completed before calling + // CopyMem(). + // + AsmLfence (); + GaugeEntryExArray = (GAUGE_DATA_ENTRY_EX *) (mGaugeData + 1); for (Index = 0; Index < NumberOfEntries; Index++) { -- 2.12.0.windows.1 _______________________________________________ edk2-devel mailing list [email protected] https://lists.01.org/mailman/listinfo/edk2-devel
