---
id: "CVE-2026-99244"
kind: "vulnerability"
aliases: ["CVE-2026-99244"]
title: "Linux kernel: PID namespace reaper can busy-wait instead of sleeping"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["containers", "linux-kernel", "livepatch", "runtime"]
not_affected_if: []
published_at: "2026-11-03T12:17:30+00:00"
first_seen_at: "2026-11-03T12:20:38+00:00"
updated_at: "2026-11-03T12:23:03+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-99244", "first_seen_at": "2026-11-03T12:20:38+00:00"}]
---

# Linux kernel: PID namespace reaper can busy-wait instead of sleeping

In the Linux kernel, the PID namespace reaper could be interrupted by a TIF_NOTIFY_SIGNAL flag that is raised again during livepatching, so it busy-waits instead of sleeping. The fix makes the reaper ignore that flag so it sleeps until a child exits.

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

## Timeline

- 2026-11-03T12:20:38+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-99244

## From the sources

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

pid_namespace: prevent TIF_NOTIFY_SIGNAL from interrupting the reaper

Since commit 7fea700e04bd ("zap_pid_ns_processes: clear
TIF_NOTIFY_SIGNAL along with TIF_SIGPENDING") zap_pid_ns_processes()
clears TIF_NOTIFY_SIGNAL before every kernel_wait4() call. Otherwise
kernel_wait4() doesn't sleep and returns -ERESTARTSYS if
signal_pending() is true and the reaper busy-waits.

But clearing TIF_NOTIFY_SIGNAL doesn't fix it. It can get raised again.
For example, klp_send_signals() sets it raw against any task that hasn't
transitioned yet. And it keeps sending it until the livepatch finishes.

The sleep loop waiting for pid_allocated to drop has the same problem
and it doesn't even clear anything. So a schedule() in
TASK_INTERRUPTIBLE returns immediately.

Use a no_notify_signal guard. signal_pending() will ignore
TIF_NOTIFY_SIGNAL and the pid namespace reaper sleeps until a child
exits or free_pid() wakes it.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_