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authorJosh Poimboeuf2022-02-25 14:32:28 -0800
committerBorislav Petkov2022-03-05 09:30:47 +0100
commit0de05d056afdb00eca8c7bbb0c79a3438daf700c (patch)
tree5d7e315e4956d1294428564823b3a0e01fa25609 /kernel/entry
parenteafd987d4a82c7bb5aa12f0e3b4f8f3dea93e678 (diff)
x86/speculation: Warn about eIBRS + LFENCE + Unprivileged eBPF + SMT
The commit 44a3918c8245 ("x86/speculation: Include unprivileged eBPF status in Spectre v2 mitigation reporting") added a warning for the "eIBRS + unprivileged eBPF" combination, which has been shown to be vulnerable against Spectre v2 BHB-based attacks. However, there's no warning about the "eIBRS + LFENCE retpoline + unprivileged eBPF" combo. The LFENCE adds more protection by shortening the speculation window after a mispredicted branch. That makes an attack significantly more difficult, even with unprivileged eBPF. So at least for now the logic doesn't warn about that combination. But if you then add SMT into the mix, the SMT attack angle weakens the effectiveness of the LFENCE considerably. So extend the "eIBRS + unprivileged eBPF" warning to also include the "eIBRS + LFENCE + unprivileged eBPF + SMT" case. [ bp: Massage commit message. ] Suggested-by: Alyssa Milburn <alyssa.milburn@linux.intel.com> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Borislav Petkov <bp@suse.de>
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