Got it. Since the patches have already been checked in. I will follow this style next time.
Best Regards, Hao Wu > -----Original Message----- > From: Gao, Liming > Sent: Wednesday, November 21, 2018 2:16 PM > To: Wu, Hao A; edk2-devel@lists.01.org > Cc: Wu, Hao A; Laszlo Ersek; Yao, Jiewen; Zeng, Star > Subject: RE: [edk2] [PATCH v2 1/2] MdeModulePkg/SmmCorePerfLib: [CVE- > 2017-5753] Fix bounds check bypass > > Hao: > In previous discussion, the suggested subject style is > MdeModulePkg/SmmCorePerfLib: Fix bounds check bypass(CVE-2017-5753). > > Thanks > Liming > > -----Original Message----- > > From: edk2-devel [mailto:edk2-devel-boun...@lists.01.org] On Behalf Of > Hao Wu > > Sent: Friday, November 16, 2018 12:13 PM > > To: edk2-devel@lists.01.org > > Cc: Wu, Hao A <hao.a...@intel.com>; Laszlo Ersek <ler...@redhat.com>; > Yao, Jiewen <jiewen....@intel.com>; Zeng, Star > > <star.z...@intel.com> > > Subject: [edk2] [PATCH v2 1/2] MdeModulePkg/SmmCorePerfLib: [CVE- > 2017-5753] Fix bounds check bypass > > > > 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 > > SmmCorePerformanceLib and insert AsmLfence API to mitigate the > bounds > > check bypass issue. > > > > For SMI handler SmmPerformanceHandlerEx(): > > > > Under "case SMM_PERF_FUNCTION_GET_GAUGE_DATA :", > > 'SmmPerfCommData->LogEntryKey' can be a potential cross boundary > access of > > the 'CommBuffer' (controlled external inputs) during speculative > > execution. This cross boundary access is then assign to parameter > > 'LogEntryKey'. And the value of 'LogEntryKey' can be inferred by code: > > > > CopyMem ( > > (UINT8 *) &GaugeDataEx[Index], > > (UINT8 *) &GaugeEntryExArray[LogEntryKey++], > > sizeof (GAUGE_DATA_ENTRY_EX) > > ); > > > > One can observe which part of the content within 'GaugeEntryExArray' was > > brought into cache to possibly reveal the value of 'LogEntryKey'. > > > > Hence, this commit adds a AsmLfence() after the boundary/range checks > of > > 'CommBuffer' to prevent the speculative execution. > > > > And there is 1 similar case for SMI handler SmmPerformanceHandler() as > > well. This commit also handles it. > > > > 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- > vuln > > erabilities.pdf > > > > Cc: Star Zeng <star.z...@intel.com> > > Cc: Jiewen Yao <jiewen....@intel.com> > > Cc: Laszlo Ersek <ler...@redhat.com> > > Contributed-under: TianoCore Contribution Agreement 1.1 > > Signed-off-by: Hao Wu <hao.a...@intel.com> > > --- > > > MdeModulePkg/Library/SmmCorePerformanceLib/SmmCorePerformanceLi > b.c | 16 +++++++++++++++- > > 1 file changed, 15 insertions(+), 1 deletion(-) > > > > diff --git > a/MdeModulePkg/Library/SmmCorePerformanceLib/SmmCorePerformance > Lib.c > > > b/MdeModulePkg/Library/SmmCorePerformanceLib/SmmCorePerformance > Lib.c > > index cd1f1a5d5f..63c1eea3a2 100644 > > --- > a/MdeModulePkg/Library/SmmCorePerformanceLib/SmmCorePerformance > Lib.c > > +++ > b/MdeModulePkg/Library/SmmCorePerformanceLib/SmmCorePerformance > Lib.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 > > edk2-devel@lists.01.org > > https://lists.01.org/mailman/listinfo/edk2-devel _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
