The vulnerability in the Linux kernel's sched_ext component was due to an incorrect locking order in the scx_cgroup_lock() function. The function originally write-locked scx_cgroup_ops_rwsem before acquiring cgroup_lock(), which could cause a deadlock involving cgroup_mutex and kernfs locks during operations such as enabling/disabling sched_ext, cgroup directory removal, and cpu.weight writes. The deadlock arises because the enable path waits for rmdir to release cgroup_mutex, rmdir waits in kernfs_drain() for an active reference held by the write operation, and the write operation waits on the rwsem locked by the pending writer. The fix changes the locking order to acquire cgroup_lock() first, ensuring that pending write-locks only wait for read sections that complete without circular dependencies, thus eliminating the deadlock.

This vulnerability could cause a kernel deadlock, potentially leading to system hangs or denial of service conditions when the affected locking sequence is triggered. There is no indication of privilege escalation or code execution impact. No known exploits in the wild have been reported.

A fix has been implemented that changes the locking order in scx_cgroup_lock() to acquire cgroup_lock() first, preventing the deadlock. Users should update their Linux kernel to a version that includes this fix once available. Patch status is not yet confirmed from vendor advisories; check official Linux kernel release notes or vendor advisories for the fixed versions and apply updates accordingly.