sched_ext: Fix this_rq() assumptions in dispatch kfuncs

{
  "id": "828e66e673067752d2fc88e41d96546dc845e8b84d1287d2a3bab449696e8be9",
  "url": "https://osv.dev/vulnerability/CVE-2026-89518",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "sched_ext: Fix this_rq() assumptions in dispatch kfuncs",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: sched_ext: Fix this_rq() assumptions in dispatch kfuncs Under core scheduling, dispatch runs from within the core-wide pick and can target a sibling rq, so ops.dispatch() may execute on a CPU different from the dispatched rq's. Several kfunc paths assumed the two always coincide: - scx_dsq_move() decided whether an rq lock is held by testing this_rq()'s rq flags and lock-danced accordingly. A dispatch for a sibling took the unlocked-context branch and acquired the source rq lock on top of the already held dispatched rq lock which could deadlock. - scx_bpf_sub_dispatch() dispatched this_rq() with its stashed sub_dispatch_prev, which is NULL when dispatching for a sibling. - finish_dispatch(), scx_bpf_dsq_reenq() and scx_bpf_dsq_nr_queued() resolved SCX_DSQ_LOCAL to this CPU's local DSQ rather than the dispatched rq's. The latter two are callable from other rq-locked operations too, where SCX_DSQ_LOCAL now likewise resolves to the op's rq. This changes behavior also without core scheduling, e.g. for ops.enqueue() running a remote wakeup on the waking CPU, and is intended: which CPU happens to execute an operation is incidental, the op's rq is what it is operating on, and the resolution now matches the insert side where SCX_DSQ_LOCAL dispatches land on the task's rq. Use the rq tracked by scx_locked_rq(), which is set to the dispatched rq around ops invocations and NULL in unlocked contexts.",
    "evidence": "osv:CVE-2026-89518",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "7.2.4",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-89518",
      "aliases": [
        "CVE-2026-89518"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "4c95380701f58b8112f0b891de8d160e4199e19d"
                },
                {
                  "fixed": "6d1890d3c6137ab523799765ae2de62cc05f116d"
                },
                {
                  "fixed": "3dd52416e44a70bc993adb96d2e0d71b9ea21359"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89518.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.2.4"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89518.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:32.296590923Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/3dd52416e44a70bc993adb96d2e0d71b9ea21359",
        "https://git.kernel.org/stable/c/6d1890d3c6137ab523799765ae2de62cc05f116d",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89518.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-89518",
        "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/2026/89xxx/CVE-2026-89518.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-89518",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 499598,
  "published_at": "2026-09-11T19:44:01.222+00:00"
}