mm: fix crashes from deferred split racing folio migration

{
  "id": "239e8f70385ead78964abb57d51839abce2f3fd10d30239c47394b7f6c76ebed",
  "url": "https://osv.dev/vulnerability/CVE-2024-42234",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "mm: fix crashes from deferred split racing folio migration",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: mm: fix crashes from deferred split racing folio migration Even on 6.10-rc6, I've been seeing elusive \"Bad page state\"s (often on flags when freeing, yet the flags shown are not bad: PG_locked had been set and cleared??), and VM_BUG_ON_PAGE(page_ref_count(page) == 0)s from deferred_split_scan()'s folio_put(), and a variety of other BUG and WARN symptoms implying double free by deferred split and large folio migration. 6.7 commit 9bcef5973e31 (\"mm: memcg: fix split queue list crash when large folio migration\") was right to fix the memcg-dependent locking broken in 85ce2c517ade (\"memcontrol: only transfer the memcg data for migration\"), but missed a subtlety of deferred_split_scan(): it moves folios to its own local list to work on them without split_queue_lock, during which time folio->_deferred_list is not empty, but even the \"right\" lock does nothing to secure the folio and the list it is on. Fortunately, deferred_split_scan() is careful to use folio_try_get(): so folio_migrate_mapping() can avoid the race by folio_undo_large_rmappable() while the old folio's reference count is temporarily frozen to 0 - adding such a freeze in the !mapping case too (originally, folio lock and unmapping and no swap cache left an anon folio unreachable, so no freezing was needed there: but the deferred split queue offers a way to reach it).",
    "evidence": "osv:CVE-2024-42234",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.9.10",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2024-42234",
      "aliases": [
        "CVE-2024-42234"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "9bcef5973e31020e5aa8571eb994d67b77318356"
                },
                {
                  "fixed": "fc7facce686b64201dbf0b9614cc1d0bfad70010"
                },
                {
                  "fixed": "be9581ea8c058d81154251cb0695987098996cad"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2024-42234.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.7.0"
                },
                {
                  "fixed": "6.9.10"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2024-42234.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:36.982064447Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/be9581ea8c058d81154251cb0695987098996cad",
        "https://git.kernel.org/stable/c/fc7facce686b64201dbf0b9614cc1d0bfad70010",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/42xxx/CVE-2024-42234.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2024-42234",
        "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/2024/42xxx/CVE-2024-42234.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2024-42234",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 504060,
  "published_at": "2024-08-07T15:14:24.467+00:00"
}