{"id":"CVE-2026-68421","state":"PUBLISHED","title":"sched_ext: Don't warn on core-sched forced idle in put_prev_task_scx()","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nsched_ext: Don't warn on core-sched forced idle in put_prev_task_scx()\n\nput_prev_task_scx() warns when a runnable task drops to a lower sched_class\nwithout SCX_OPS_ENQ_LAST, on the assumption that balance_one() would have\nkept it running. Core scheduling breaks that: a forced-idle SMT sibling\nreschedules through the core_pick fast path in pick_next_task(), which skips\npick_task_scx() and thus balance_one(), so a runnable task can drop to idle\nwith ENQ_LAST unset.\n\nGate the warning on sched_cpu_cookie_match(): a cookie mismatch means core\nscheduling forced the idle, while a match (or core scheduling off) still\ncatches a genuine missing-ENQ_LAST drop.","publishedAt":"2026-08-10T12:04:41.946Z","updatedAt":"2026-10-21T12:44:06.128Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"7c65ae81ea86a6ed8086e1a5651acd766187f19b","status":"affected","lessThan":"6267ebee9f2f3e26f4968bf6dc29d350620fa320","versionType":"git"},{"version":"7c65ae81ea86a6ed8086e1a5651acd766187f19b","status":"affected","lessThan":"2907e9d0f05b506dfd58aec589a23042a56ef36b","versionType":"git"},{"version":"7c65ae81ea86a6ed8086e1a5651acd766187f19b","status":"affected","lessThan":"e2f188cdbf8312289532c36eb4e9eb1c9544d43a","versionType":"git"},{"version":"7c65ae81ea86a6ed8086e1a5651acd766187f19b","status":"affected","lessThan":"b7d9c359e5cf867f7eb23df3bb1c6b9e58af24da","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/sched/ext/ext.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.12","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.12","versionType":"semver"},{"version":"6.12.114","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.42","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.6","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/sched/ext/ext.c"]}],"references":["https://git.kernel.org/stable/c/6267ebee9f2f3e26f4968bf6dc29d350620fa320","https://git.kernel.org/stable/c/2907e9d0f05b506dfd58aec589a23042a56ef36b","https://git.kernel.org/stable/c/e2f188cdbf8312289532c36eb4e9eb1c9544d43a","https://git.kernel.org/stable/c/b7d9c359e5cf867f7eb23df3bb1c6b9e58af24da"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:49.727Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/68xxx/CVE-2026-68421.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-68421","state":"PUBLISHED","datePublished":"2026-08-10T12:04:41.946Z","dateUpdated":"2026-10-21T12:44:06.128Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-07-30T09:28:09.392Z"},"containers":{"cna":{"title":"sched_ext: Don't warn on core-sched forced idle in put_prev_task_scx()","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nsched_ext: Don't warn on core-sched forced idle in put_prev_task_scx()\n\nput_prev_task_scx() warns when a runnable task drops to a lower sched_class\nwithout SCX_OPS_ENQ_LAST, on the assumption that balance_one() would have\nkept it running. Core scheduling breaks that: a forced-idle SMT sibling\nreschedules through the core_pick fast path in pick_next_task(), which skips\npick_task_scx() and thus balance_one(), so a runnable task can drop to idle\nwith ENQ_LAST unset.\n\nGate the warning on sched_cpu_cookie_match(): a cookie mismatch means core\nscheduling forced the idle, while a match (or core scheduling off) still\ncatches a genuine missing-ENQ_LAST drop."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"7c65ae81ea86a6ed8086e1a5651acd766187f19b","status":"affected","lessThan":"6267ebee9f2f3e26f4968bf6dc29d350620fa320","versionType":"git"},{"version":"7c65ae81ea86a6ed8086e1a5651acd766187f19b","status":"affected","lessThan":"2907e9d0f05b506dfd58aec589a23042a56ef36b","versionType":"git"},{"version":"7c65ae81ea86a6ed8086e1a5651acd766187f19b","status":"affected","lessThan":"e2f188cdbf8312289532c36eb4e9eb1c9544d43a","versionType":"git"},{"version":"7c65ae81ea86a6ed8086e1a5651acd766187f19b","status":"affected","lessThan":"b7d9c359e5cf867f7eb23df3bb1c6b9e58af24da","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/sched/ext/ext.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.12","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.12","versionType":"semver"},{"version":"6.12.114","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.42","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.6","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/sched/ext/ext.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/6267ebee9f2f3e26f4968bf6dc29d350620fa320"},{"url":"https://git.kernel.org/stable/c/2907e9d0f05b506dfd58aec589a23042a56ef36b"},{"url":"https://git.kernel.org/stable/c/e2f188cdbf8312289532c36eb4e9eb1c9544d43a"},{"url":"https://git.kernel.org/stable/c/b7d9c359e5cf867f7eb23df3bb1c6b9e58af24da"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-21T12:44:06.128Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12","versionEndExcluding":"6.12.114"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12","versionEndExcluding":"6.18.42"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12","versionEndExcluding":"7.1.6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12","versionEndExcluding":"7.2"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}