CVE-2021-46997

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

arm64: entry: always set GIC_PRIO_PSR_I_SET during entry

Zenghui reports that booting a kernel with "irqchip.gicv3_pseudo_nmi=1"

on the command line hits a warning during kernel entry, due to the way

we manipulate the PMR.

Early in the entry sequence, we call lockdep_hardirqs_off() to inform

lockdep that interrupts have been masked (as the HW sets DAIF wqhen

entering an exception). Architecturally PMR_EL1 is not affected by

exception entry, and we don't set GIC_PRIO_PSR_I_SET in the PMR early in

the exception entry sequence, so early in exception entry the PMR can

indicate that interrupts are unmasked even though they are masked by

DAIF.

If DEBUG_LOCKDEP is selected, lockdep_hardirqs_off() will check that

interrupts are masked, before we set GIC_PRIO_PSR_I_SET in any of the

exception entry paths, and hence lockdep_hardirqs_off() will WARN() that

something is amiss.

We can avoid this by consistently setting GIC_PRI

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References