A flaw was found in hw. The Intra-mode BTI refers to a variant of Branch Target Injection aka SpectreV2 (BTI) where an indirect branch speculates to an aliased predictor entry for a different indirect branch in the same predictor mode, and a disclosure gadget at the predicted target transiently executes. These predictor entries may contain targets corresponding to the targets of an indirect near jump, indirect near call, and near return instructions, even if these branches were only transiently executed. The managed runtimes provide an attacker with the means to create the aliasing required for intra-mode BTI attacks.

Mitigation

Disabling unprivileged eBPF effectively mitigates the known attack vectors for exploiting intra-mode branch injections attacks.

The default Red Hat Enterprise Linux kernel prevents unprivileged users from being able to use eBPF by the kernel.unprivileged_bpf_disabled sysctl.

For the Red Hat Enterprise Linux 7 the eBPF for unprivileged users is always disabled.

For the Red Hat Enterprise Linux 8 to confirm the current state, inspect the sysctl with the command:

cat /proc/sys/kernel/unprivileged_bpf_disabled

The setting of 1 would mean that unprivileged users can not use eBPF, mitigating the flaw.

Continue to enable SMEP and Enhanced IBRS. This is the default setting on eligible CPUs.