mm: swap_cgroup: fix NULL deref in lookup_swap_cgroup_id on swapless host

{
  "id": "bed48eb97c0d6fd704deb7ca3165bc282f6b5e8b9f345c40ea20e8f99f0ac52d",
  "url": "https://osv.dev/vulnerability/CVE-2026-64416",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "mm: swap_cgroup: fix NULL deref in lookup_swap_cgroup_id on swapless host",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: mm: swap_cgroup: fix NULL deref in lookup_swap_cgroup_id on swapless host lookup_swap_cgroup_id() passes swap_cgroup_ctrl[type].map to __swap_cgroup_id_lookup() without checking that the type was ever registered via swap_cgroup_swapon(). On a swapless host every ctrl->map is NULL, so __swap_cgroup_id_lookup() dereferences NULL + a scaled swp_offset(). Since commit bea67dcc5eea (\"mm: attempt to batch free swap entries for zap_pte_range()\"), zap_pte_range() -> swap_pte_batch() calls lookup_swap_cgroup_id() on any non-present, non-none PTE that decodes as a real swap entry, without first validating it against swap_info[]. A single PTE corrupted into a type-0 swap entry takes the host down at process exit. We hit this in production on a swapless 6.12.58 host: ~1s of \"get_swap_device: Bad swap file entry 3f800204222bb\" (do_swap_page() being correctly defensive about the same entry) followed by BUG: unable to handle page fault for address: 000003f800204220 RIP: 0010:lookup_swap_cgroup_id+0x2b/0x60 Call Trace: swap_pte_batch+0xbf/0x230 zap_pte_range+0x4c8/0x780 unmap_page_range+0x190/0x3e0 exit_mmap+0xd9/0x3c0 do_exit+0x20c/0x4b0 syzbot has reported the identical stack. The source of the PTE corruption is a separate bug; this change makes the teardown path as robust as the fault path already is. Every other caller of lookup_swap_cgroup_id() is downstream of a get_swap_device() that has already validated the entry, s",
    "evidence": "osv:CVE-2026-64416",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.12.97",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.39",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.1.4",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-64416",
      "aliases": [
        "CVE-2026-64416"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
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                {
                  "fixed": "818416fef38759f23210de449663cd9d7e293d39"
                },
                {
                  "fixed": "b415c00bf23df577a4a95673d00ae76687bcc1d4"
                },
                {
                  "fixed": "6a4196d19f477524d2f92adca90fc1fbe9a0420a"
                },
                {
                  "fixed": "63b02a9409cb5180398491b093e48bcb5315f5fb"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-64416.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.12.0"
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                {
                  "fixed": "6.12.97"
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            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
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                {
                  "fixed": "6.18.39"
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              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.1.4"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-64416.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:50.516927720Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/63b02a9409cb5180398491b093e48bcb5315f5fb",
        "https://git.kernel.org/stable/c/6a4196d19f477524d2f92adca90fc1fbe9a0420a",
        "https://git.kernel.org/stable/c/818416fef38759f23210de449663cd9d7e293d39",
        "https://git.kernel.org/stable/c/b415c00bf23df577a4a95673d00ae76687bcc1d4",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64416.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-64416",
        "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/2026/64xxx/CVE-2026-64416.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-64416",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 518678,
  "published_at": "2026-07-25T08:50:55.997+00:00"
}