CVE-2026-68421

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

sched_ext: Don't warn on core-sched forced idle in put_prev_task_scx()

put_prev_task_scx() warns when a runnable task drops to a lower sched_class

without SCX_OPS_ENQ_LAST, on the assumption that balance_one() would have

kept it running. Core scheduling breaks that: a forced-idle SMT sibling

reschedules through the core_pick fast path in pick_next_task(), which skips

pick_task_scx() and thus balance_one(), so a runnable task can drop to idle

with ENQ_LAST unset.

Gate the warning on sched_cpu_cookie_match(): a cookie mismatch means core

scheduling forced the idle, while a match (or core scheduling off) still

catches a genuine missing-ENQ_LAST drop.