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

{
  "id": "e18412344f3711dcee4ebc3f29ba7ff16c3f20699fa39463a8e50d8763f2697a",
  "url": "https://osv.dev/vulnerability/CVE-2026-68421",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "sched_ext: Don't warn on core-sched forced idle in put_prev_task_scx()",
    "summary": "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.",
    "evidence": "osv:CVE-2026-68421",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.12.114",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.42",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.1.6",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-68421",
      "aliases": [
        "CVE-2026-68421"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "7c65ae81ea86a6ed8086e1a5651acd766187f19b"
                },
                {
                  "fixed": "6267ebee9f2f3e26f4968bf6dc29d350620fa320"
                },
                {
                  "fixed": "2907e9d0f05b506dfd58aec589a23042a56ef36b"
                },
                {
                  "fixed": "e2f188cdbf8312289532c36eb4e9eb1c9544d43a"
                },
                {
                  "fixed": "b7d9c359e5cf867f7eb23df3bb1c6b9e58af24da"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-68421.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.12.0"
                },
                {
                  "fixed": "6.12.114"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.18.42"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.1.6"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-68421.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:36.032239387Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/2907e9d0f05b506dfd58aec589a23042a56ef36b",
        "https://git.kernel.org/stable/c/6267ebee9f2f3e26f4968bf6dc29d350620fa320",
        "https://git.kernel.org/stable/c/b7d9c359e5cf867f7eb23df3bb1c6b9e58af24da",
        "https://git.kernel.org/stable/c/e2f188cdbf8312289532c36eb4e9eb1c9544d43a",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/68xxx/CVE-2026-68421.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-68421",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/68xxx/CVE-2026-68421.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-68421",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 503473,
  "published_at": "2026-08-10T12:04:41.946+00:00"
}