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Inspectre Gadget – New BHI Related Research
Announcement ID:
2024-04-09.001
Issue:
On April 9, 2024, External researchers from VU Amsterdam have proposed new software techniques to identify and potentially exploit disclosure gadgets using the previously disclosed Branch History Injection (BHI) vulnerability. BHI was a cross-domain transient execution attack related to Branch Target Injection (BTI) commonly known as “Spectre v2”. They are referring to this attack as “Inspectre Gadget”. Previous hardware and software guidance that was provided to protect against BHI and Intramode-BTI has been updated in light of this new report. The original recommended mitigation focused on mitigating potential disclosure gadgets in Linux kernel by disabling unprivileged eBPF, continuing to enable SMEP and enhanced IBRS and adding LFENCE at the indirect branch target where a potentially exploitable disclosure gadget is identified. In the light of the new external research that has identified more native disclosure gadgets in Linux kernel, alternative mitigations may need to be considered instead of the original recommended mitigation. While this is already expected and covered by the original technical paper with other alternative mitigation options, customers may need to take action if they were using the previously recommended mitigation option.
Resolution/Recommendations:
External academic researchers report new techniques to identify BHI sequences that could allow a local attacker who can already execute code to possibly infer the contents of Linux kernel memory. Intel has previously shared mitigation guidance for BHI and intra-mode BTI attacks. In light of this new report, Intel is releasing updated guidance to assist in broader deployment of these mitigations.
Review the Branch History Injection and Intra-mode Branch Target Injection documentation linked to in the additional resources section.
Additional resources:
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