sched_ext: Fix stall when a task enqueued with SCX_ENQ_LAST lands back on its CPU's local DSQ

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Summary

CVECVE-2026-99105
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-28 11:17:29 UTC
Updated2026-10-30 13:21:45 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: sched_ext: Fix stall when a task enqueued with SCX_ENQ_LAST lands back on its CPU's local DSQ With SCX_OPS_ENQ_LAST, the last runnable task on a CPU is passed to ops.enqueue() instead of being kept running. Exiting tasks without SCX_OPS_ENQ_EXITING, migration disabled tasks without SCX_OPS_ENQ_MIGRATION_DISABLED and tasks on an offline rq skip ops.enqueue() and go straight to the local DSQ. This happens in put_prev_task_scx() after the pick has settled on idle, so nothing reschedules the CPU, which idles with the task queued until an unrelated wakeup lands on it or the watchdog fires. scx_mitosis, which sets SCX_OPS_ENQ_LAST without SCX_OPS_ENQ_EXITING, hit this during mass cgroup teardown: exiting tasks stuck in exit_mmap() for over 40 seconds. A task put on the local DSQ runs, as anywhere else. If the SCX_ENQ_LAST enqueue left the task on this CPU's local DSQ, set need_resched on the task being switched in, as proxy_resched_idle() does. resched_curr() would flag the task being put instead, and __schedule() clears that right after the pick.

Risk And Classification

EPSS: 0.001680000 probability, percentile 0.061750000 (date 2026-11-01)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected f0e1a0643a59bf1f922fa209cec86a170b784f3f ea47eec058fc1b6a3c3c54870d24a8bdcb3e204d git Not specified
CNA Linux Linux affected f0e1a0643a59bf1f922fa209cec86a170b784f3f 8d891c218016b6145993e082e7f732cb69dd0e29 git Not specified
CNA Linux Linux affected f0e1a0643a59bf1f922fa209cec86a170b784f3f 396ba6f04da3fd1fb5a3d1c9535bef3f967f4e59 git Not specified
CNA Linux Linux affected f0e1a0643a59bf1f922fa209cec86a170b784f3f 7a9df76679633cf26e0fea882a684012c6ec245a git Not specified
CNA Linux Linux affected 6.12 Not specified
CNA Linux Linux unaffected 6.12 semver Not specified
CNA Linux Linux unaffected 6.12.115 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.59 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.13 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/7a9df76679633cf26e0fea882a684012c6ec245a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/ea47eec058fc1b6a3c3c54870d24a8bdcb3e204d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/8d891c218016b6145993e082e7f732cb69dd0e29 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/396ba6f04da3fd1fb5a3d1c9535bef3f967f4e59 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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