mirror of
https://github.com/tianocore/edk2
synced 2026-08-27 00:23:19 -04:00
72d299c376
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-vulnerabilities.pdf Cc: Jiewen Yao <jiewen.yao@intel.com> Cc: Laszlo Ersek <lersek@redhat.com> Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Hao Wu <hao.a.wu@intel.com> Reviewed-by: Star Zeng <star.zeng@intel.com> |
||
|---|---|---|
| .. | ||
| Application | ||
| Bus | ||
| Core | ||
| Include | ||
| Library | ||
| Logo | ||
| Universal | ||
| Contributions.txt | ||
| License.txt | ||
| MdeModulePkg.dec | ||
| MdeModulePkg.dsc | ||
| MdeModulePkg.uni | ||
| MdeModulePkgExtra.uni | ||