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CVE-2021-46997: arm64: entry: always set GIC_PRIO_PSR_I_SET during entry

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_PRIO_PSR_I_SET during exception entry so that kernel code sees a consistent environment. We must also update local_daif_inherit() to undo this, as currently only touches DAIF. For other paths, local_daif_restore() will update both DAIF and the PMR. With this done, we can remove the existing special cases which set this later in the entry code. We always use (GIC_PRIO_IRQON | GIC_PRIO_PSR_I_SET) for consistency with local_daif_save(), as this will warn if it ever encounters (GIC_PRIO_IRQOFF | GIC_PRIO_PSR_I_SET), and never sets this itself. This matches the gic_prio_kentry_setup that we have to retain for ret_to_user. The original splat from Zenghui's report was: | DEBUG_LOCKS_WARN_ON(!irqs_disabled()) | WARNING: CPU: 3 PID: 125 at kernel/locking/lockdep.c:4258 lockdep_hardirqs_off+0xd4/0xe8 | Modules linked in: | CPU: 3 PID: 125 Comm: modprobe Tainted: G W 5.12.0-rc8+ #463 | Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015 | pstate: 604003c5 (nZCv DAIF +PAN -UAO -TCO BTYPE=--) | pc : lockdep_hardirqs_off+0xd4/0xe8 | lr : lockdep_hardirqs_off+0xd4/0xe8 | sp : ffff80002a39bad0 | pmr_save: 000000e0 | x29: ffff80002a39bad0 x28: ffff0000de214bc0 | x27: ffff0000de1c0400 x26: 000000000049b328 | x25: 0000000000406f30 x24: ffff0000de1c00a0 | x23: 0000000020400005 x22: ffff8000105f747c | x21: 0000000096000044 x20: 0000000000498ef9 | x19: ffff80002a39bc88 x18: ffffffffffffffff | x17: 0000000000000000 x16: ffff800011c61eb0 | x15: ffff800011700a88 x14: 0720072007200720 | x13: 0720072007200720 x12: 0720072007200720 | x11: 0720072007200720 x10: 0720072007200720 | x9 : ffff80002a39bad0 x8 : ffff80002a39bad0 | x7 : ffff8000119f0800 x6 : c0000000ffff7fff | x5 : ffff8000119f07a8 x4 : 0000000000000001 | x3 : 9bcdab23f2432800 x2 : ffff800011730538 | x1 : 9bcdab23f2432800 x0 : 0000000000000000 | Call trace: | lockdep_hardirqs_off+0xd4/0xe8 | enter_from_kernel_mode.isra.5+0x7c/0xa8 | el1_abort+0x24/0x100 | el1_sync_handler+0x80/0xd0 | el1_sync+0x6c/0x100 | __arch_clear_user+0xc/0x90 | load_elf_binary+0x9fc/0x1450 | bprm_execve+0x404/0x880 | kernel_execve+0x180/0x188 | call_usermodehelper_exec_async+0xdc/0x158 | ret_from_fork+0x10/0x18

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysislow

Security readout for executives and security teams

Plain-English summary

This Linux kernel issue affects ARM64 exception entry handling when GICv3 pseudo-NMI support is enabled. The documented effect is a kernel lockdep warning caused by inconsistent interrupt state reporting, not a confirmed remote compromise path. Business urgency is mainly for ARM64 fleets running affected kernels with this configuration.

Executive priority

Treat as a low-priority kernel maintenance item unless your environment runs ARM64 systems with the affected interrupt configuration. Fold remediation into normal kernel update cycles, with higher priority for platforms showing the warning or using custom/debug kernels.

Technical view

On ARM64, exception entry masked interrupts through DAIF but did not immediately reflect that state in PMR_EL1. With DEBUG_LOCKDEP and irqchip.gicv3_pseudo_nmi=1, lockdep_hardirqs_off() could warn before PMR was updated. The fix consistently sets GIC_PRIO_PSR_I_SET during entry and adjusts local_daif_inherit().

Likely exposure

Exposure appears limited to Linux kernel ARM64 systems, especially those using GICv3 pseudo-NMI behavior. The provided affected data references Linux 5.10-era stable lines and kernel commits, but exact distribution package impact must be confirmed with vendor advisories.

Exploitation context

The source bundle does not show active exploitation, KEV listing, public exploit use, or a practical attacker path. The reported symptom is a warning during kernel entry under a specific configuration, observed in a QEMU KVM ARM64 environment.

Researcher notes

Evidence supports an ARM64 interrupt-state consistency bug fixed upstream. The bundle lacks CVSS, CWE, exploitability analysis, and distribution-specific affected package data. Do not infer remote code execution, privilege escalation, or active exploitation from the provided sources.

Mitigation direction

  • Apply Linux vendor kernel updates containing the referenced stable fixes.
  • Prioritize ARM64 systems using GICv3 pseudo-NMI or DEBUG_LOCKDEP kernels.
  • If patch timing is unclear, check distribution advisories for CVE-2021-46997 mapping.
  • Avoid claiming remediation from configuration changes unless vendor guidance supports it.

Validation and detection

  • Inventory ARM64 Linux kernels and compare versions against vendor CVE advisories.
  • Check boot configuration for irqchip.gicv3_pseudo_nmi=1 usage.
  • Review kernel logs for the documented lockdep_hardirqs_off warning pattern.
  • Confirm deployed kernels include one of the referenced upstream stable commits.
Prepared
Confidence
medium
Sources
6

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
2ADP providers
5Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

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other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux23529049c68423820487304f244144e0d576e85a, 23529049c68423820487304f244144e0d576e85a, 23529049c68423820487304f244144e0d576e85a, 23529049c68423820487304f244144e0d576e85aunaffected
LinuxLinux5.10, 0, 5.10.38, 5.11.22, 5.12.5, 5.13affected
Weakness

CWE details

No CWE listed

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