CVE-2025-38522

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

sched/ext: Prevent updatelockedrq() calls with NULL rq

Avoid invoking updatelockedrq() when the runqueue (rq) pointer is NULL in the SCXCALLOP and SCXCALLOP_RET macros.

Previously, calling updatelockedrq(NULL) with preemption enabled could trigger the following warning:

BUG: using __this_cpu_write() in preemptible [00000000]

This happens because __thiscpuwrite() is unsafe to use in preemptible context.

rq is NULL when an ops invoked from an unlocked context. In such cases, we don't need to store any rq, since the value should already be NULL (unlocked). Ensure that updatelockedrq() is only called when rq is non-NULL, preventing calling __thiscpuwrite() on preemptible context.