sched_ext: Fix SCX_KICK_WAIT deadlock by deferring wait to balance callback

{
  "id": "caa84a9629f48ea4a3d861028c69cb0529af1664f5bd1f3a356677fd7813e6e8",
  "url": "https://osv.dev/vulnerability/CVE-2026-43326",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "sched_ext: Fix SCX_KICK_WAIT deadlock by deferring wait to balance callback",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: sched_ext: Fix SCX_KICK_WAIT deadlock by deferring wait to balance callback SCX_KICK_WAIT busy-waits in kick_cpus_irq_workfn() using smp_cond_load_acquire() until the target CPU's kick_sync advances. Because the irq_work runs in hardirq context, the waiting CPU cannot reschedule and its own kick_sync never advances. If multiple CPUs form a wait cycle, all CPUs deadlock. Replace the busy-wait in kick_cpus_irq_workfn() with resched_curr() to force the CPU through do_pick_task_scx(), which queues a balance callback to perform the wait. The balance callback drops the rq lock and enables IRQs following the sched_core_balance() pattern, so the CPU can process IPIs while waiting. The local CPU's kick_sync is advanced on entry to do_pick_task_scx() and continuously during the wait, ensuring any CPU that starts waiting for us sees the advancement and cannot form cyclic dependencies.",
    "evidence": "osv:CVE-2026-43326",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.19.12",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-43326",
      "aliases": [
        "CVE-2026-43326"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "90e55164dad42c6546b698c031697b224a320834"
                },
                {
                  "fixed": "c3a7903f65cf4c7fb0477eb0f8b94f326a47fe54"
                },
                {
                  "fixed": "415cb193bb9736f0e830286c72a6fa8eb2a9cc5c"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-43326.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.12.0"
                },
                {
                  "fixed": "6.19.12"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-43326.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:37.826887865Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/415cb193bb9736f0e830286c72a6fa8eb2a9cc5c",
        "https://git.kernel.org/stable/c/c3a7903f65cf4c7fb0477eb0f8b94f326a47fe54",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43326.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-43326",
        "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/2026/43xxx/CVE-2026-43326.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-43326",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 505080,
  "published_at": "2026-05-08T13:31:10.184+00:00"
}