sched/core: Handle pick_task() releasing the rq lock

Summary

In the Linux kernel, the following vulnerability has been resolved: sched/core: Handle pick_task() releasing the rq lock Core scheduling's pick_next_task() breaks when a ->pick_task() implementation can release the rq lock. The selection state derived on entry is only valid while the lock is held continuously. Once a pick can drop the lock, an interleaving selection can invalidate all of it: the single-CPU fast path can commit an uncookied pick although the core went cookied during the release, and forceidle committed by the interleaving selection skews the restarted pass's accounting. Fix it by restarting the whole selection when a pick returns RETRY_TASK after releasing the lock: a single restart point above the state derivation replaces the per-loop restart labels, so a retry picks up state committed by interleaving selections and accounts and resets forceidle like a fresh selection would. need_sync and fi_before latch across retries. Clock validity can't be re-derived - there is no program-ordered way to tell whether the own and core rq clocks are still updated after the lock was released, as other lockers' pin cycles may or may not have invalidated them. When restarting, clear core_clock_updated so that the sibling loop re-updates the core rq, and update the own rq clock if invalidated.

Timeline

1. Sep 11, 2026, 7:44 PM UTCCVE published
2. Oct 19, 2026, 8:48 AM UTCRecord last updated

Affected versions

• Linux Linux

  From 4c95380701f58b8112f0b891de8d160e4199e19d · fixed in 88ed5a66467ca2a5148b9997af9c71d8c43060ad; From 4c95380701f58b8112f0b891de8d160e4199e19d · fixed in c10b216a072ff5c57bc880a05f87eb519aecc529

• Linux Linux

  6.19

• KernelLinux

  From 6.19.0 · fixed in 7.2.4

References 2