sched_ext: Fix stale direct dispatch state in ddsp_dsq_id

{
  "id": "9bf9cfb4e442311a27ce684c27a2c1ab43f61414ecd83962adec5065f865c631",
  "url": "https://osv.dev/vulnerability/CVE-2026-31733",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "sched_ext: Fix stale direct dispatch state in ddsp_dsq_id",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: sched_ext: Fix stale direct dispatch state in ddsp_dsq_id @p->scx.ddsp_dsq_id can be left set (non-SCX_DSQ_INVALID) triggering a spurious warning in mark_direct_dispatch() when the next wakeup's ops.select_cpu() calls scx_bpf_dsq_insert(), such as: WARNING: kernel/sched/ext.c:1273 at scx_dsq_insert_commit+0xcd/0x140 The root cause is that ddsp_dsq_id was only cleared in dispatch_enqueue(), which is not reached in all paths that consume or cancel a direct dispatch verdict. Fix it by clearing it at the right places: - direct_dispatch(): cache the direct dispatch state in local variables and clear it before dispatch_enqueue() on the synchronous path. For the deferred path, the direct dispatch state must remain set until process_ddsp_deferred_locals() consumes them. - process_ddsp_deferred_locals(): cache the dispatch state in local variables and clear it before calling dispatch_to_local_dsq(), which may migrate the task to another rq. - do_enqueue_task(): clear the dispatch state on the enqueue path (local/global/bypass fallbacks), where the direct dispatch verdict is ignored. - dequeue_task_scx(): clear the dispatch state after dispatch_dequeue() to handle both the deferred dispatch cancellation and the holding_cpu race, covering all cases where a pending direct dispatch is cancelled. - scx_disable_task(): clear the direct dispatch state when transitioning a task out of the current scheduler. Waking tasks may h",
    "evidence": "osv:CVE-2026-31733",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.12.82",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.22",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.19.12",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-31733",
      "aliases": [
        "CVE-2026-31733"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
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                {
                  "fixed": "5e7b2cc8fae9ec2a5bc53311191d2faaff75a4b5"
                },
                {
                  "fixed": "7ea601daa0153e19cd1c6e6b300348c70c05fe77"
                },
                {
                  "fixed": "7e0ffb72de8aa3b25989c2d980e81b829c577010"
                }
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          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-31733.json"
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          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
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            {
              "type": "ECOSYSTEM",
              "events": [
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                  "introduced": "6.13.0"
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                {
                  "fixed": "6.18.22"
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            {
              "type": "ECOSYSTEM",
              "events": [
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                  "introduced": "6.19.0"
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                {
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          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-31733.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:50.079528827Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/5e7b2cc8fae9ec2a5bc53311191d2faaff75a4b5",
        "https://git.kernel.org/stable/c/7e0ffb72de8aa3b25989c2d980e81b829c577010",
        "https://git.kernel.org/stable/c/7ea601daa0153e19cd1c6e6b300348c70c05fe77",
        "https://git.kernel.org/stable/c/ca685511f7afd42cdcbb0feea42e5d332d384251",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31733.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-31733",
        "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/2026/31xxx/CVE-2026-31733.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-31733",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 518212,
  "published_at": "2026-05-01T14:14:31.558+00:00"
}