CVE-2026-74731

/// Technical description

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

sched_ext: Skip sub-disable teardown for never-linked sub-schedulers

A sub-scheduler enable can fail before scx_link_sched() links the sched into

the hierarchy, e.g. when the parent is already being disabled, and cleanup

still runs the full scx_sub_disable().

That is racy against root disable: drain_descendants() is the only ordering

between a sub's disable-time task walk and root disable's all-task teardown,

and an unlinked sub is invisible to it. Root's teardown can thus run between

the never-linked sub's drain and its walk, exiting every task to no

scheduler.

The walk then trips the membership WARN and re-homes the exited tasks onto

the dying hierarchy, a use-after-free.

Skip the cgroup ownership reset and the task walk if @sch was never linked,

indicated by the empty ->sibling as unlinking only happens later in the same

function. The membership WARN remains valid: a linked sub is always waited

on by an ancesto

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References