CVE-2025-38632 pinmux: fix race causing mux_owner NULL with active mux_usecount
A race condition in the Linux kernel pinmux subsystem can cause a NULL pointer dereference, leading to a system crash.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-38632?
CVE-2025-38632 is a medium-severity vulnerability in Linux kernel, published on 22 Aug 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
Which versions are affected by CVE-2025-38632?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-38632?
Apply the vendor's patch.
Is CVE-2025-38632 being exploited?
There is no known exploitation of CVE-2025-38632 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-38632, DEBIAN-CVE-2025-38632, GHSA-rpg5-5rc2-v629, ROOT-OS-DEBIAN-13-CVE-2025-38632, ROOT-OS-UBUNTU-2404-CVE-2025-38632, UBUNTU-CVE-2025-38632.