---
id: "CVE-2026-98888"
kind: "vulnerability"
aliases: ["CVE-2026-98888"]
title: "Linux kernel arm64: nested kprobe hits can leave interrupts disabled"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["arm64", "kernel", "linux", "runtime"]
not_affected_if: []
published_at: "2026-10-23T12:18:22+00:00"
first_seen_at: "2026-10-23T21:57:33+00:00"
updated_at: "2026-10-25T05:00:03+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98888", "first_seen_at": "2026-10-23T21:57:33+00:00"}]
---

# Linux kernel arm64: nested kprobe hits can leave interrupts disabled

On arm64, a kprobe hit while another kprobe is single-stepping was treated as unrecoverable, and a nested hit could overwrite the saved interrupt state. The fix allows one level of reentry and preserves the outer interrupt flags, so a nested probe no longer leaves interrupts permanently masked.

_Summary, check and fix written by a model from the sources; labelled as such._

## Timeline

- 2026-10-23T21:57:33+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98888

## From the sources

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

arm64: kprobes: Allow reentering kprobes while single-stepping

A kprobe can be hit while another kprobe is in KPROBE_HIT_SS state. This
can happen when tracing or perf code runs from the debug exception path
while the first kprobe is preparing or executing its out-of-line
single-step instruction.

Currently arm64 treats a kprobe hit in KPROBE_HIT_SS as unrecoverable,
the same as a hit in KPROBE_REENTER. This is too strict. A hit in
KPROBE_HIT_SS is still a one-level reentry and can be handled by saving
the current kprobe state and setting up single-step for the new probe,
just like reentry from KPROBE_HIT_ACTIVE or KPROBE_HIT_SSDONE.

The truly unrecoverable case is hitting another kprobe while already in
KPROBE_REENTER, because the reentry save area has already been consumed.

Move KPROBE_HIT_SS to the recoverable reentry cases and leave
KPROBE_REENTER as the unrecoverable nested reentry case.

This change also requires saving saved_irqflag in struct prev_kprobe.
When a nested kprobe calls kprobes_save_local_irqflag(), it overwrites
kcb->saved_irqflag with the currently masked DAIF value, losing the
outer kprobe's original DAIF state. Without this fix, when the outer
kprobe's single-step finishes, kprobes_restore_local_irqflag() applies
the wrong DAIF mask and leaves interrupts permanently disabled.

Extend struct prev_kprobe with a saved_irqflag field and save/restore it
alongside kp and status. This ensures the outer kprobe's original
interrupt state is preserved across reentry.

This mirrors the x86 fix in commit 6a5022a56ac3
("kprobes/x86: Allow to handle reentered kprobe on single-stepping").

---

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