CVE-2025-38539

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

tracing: Add down_write(trace_event_sem) when adding trace event

When a module is loaded, it adds trace events defined by the module. It may also need to modify the modules trace printk formats to replace enum names with their values.

If two modules are loaded at the same time, the adding of the event to the ftrace_events list can corrupt the walking of the list in the code that is modifying the printk format strings and crash the kernel.

The addition of the event should take the trace_event_sem for write while it adds the new event.

Also add a lockdep_assert_held() on that semaphore in __trace_add_event_dirs() as it iterates the list.

This vulnerability arises from a race condition in the kernel tracing subsystem where trace events could be added to the global ftrace_events list without proper synchronization, leading to potential list corruption and kernel crashes. The issue is mitigated by introducing a write lock (trace_event_sem) during event registration and adding lock assertions for safety.

Exploitation requires the ability to load kernel modules, which is a highly privileged operation (root with CAP_SYS_MODULE), so the privilege requirement is rated High (PR:H).

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.