mm/page_owner: use memcg_data snapshot to avoid TOCTOU in print_page_owner_memcg()

{
  "id": "4e7d3ff5a84186446fbc00d3ddb3b2d4387138d14f2058a900ad9ce3d13dca45",
  "url": "https://osv.dev/vulnerability/CVE-2026-93216",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "mm/page_owner: use memcg_data snapshot to avoid TOCTOU in print_page_owner_memcg()",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: mm/page_owner: use memcg_data snapshot to avoid TOCTOU in print_page_owner_memcg() print_page_owner_memcg() reads page->memcg_data via READ_ONCE() at the start to guard against tail pages and NULL data. However, it later re-reads page->memcg_data locklessly in two places: 1: page_memcg_check(page) 2: PageMemcgKmem(page) (via folio_memcg_kmem(), which includes VM_BUG_ON assertions for tail pages and MEMCG_DATA_OBJEXTS) If the page is concurrently freed and reallocated as a THP tail page or slab page between these calls, the VM_BUG_ON assertions can trigger on CONFIG_DEBUG_VM=y builds, crashing the kernel. Fix both TOCTOU issues by using the memcg_data snapshot throughout.",
    "evidence": "osv:CVE-2026-93216",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.6.160",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.114",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.2.4",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-93216",
      "aliases": [
        "CVE-2026-93216"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "fcf8935832b86d3437f00e732c6d0d4d2819d6a9"
                },
                {
                  "fixed": "e7c1923c5f30a6953f0540e3171d882ec17b05d3"
                },
                {
                  "fixed": "a4c940ab3f794f221a338c9431ad1ce0d73a2bea"
                },
                {
                  "fixed": "46761406e14381dc35f498c247a87565b87ea2ef"
                },
                {
                  "fixed": "90f095b816e25c6a9e4446d299bac5007fdcb3df"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-93216.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.18.0"
                },
                {
                  "fixed": "6.6.160"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.7.0"
                },
                {
                  "fixed": "6.12.114"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "7.2.4"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-93216.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:27.648331264Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/46761406e14381dc35f498c247a87565b87ea2ef",
        "https://git.kernel.org/stable/c/90f095b816e25c6a9e4446d299bac5007fdcb3df",
        "https://git.kernel.org/stable/c/a4c940ab3f794f221a338c9431ad1ce0d73a2bea",
        "https://git.kernel.org/stable/c/e7c1923c5f30a6953f0540e3171d882ec17b05d3",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/93xxx/CVE-2026-93216.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-93216",
        "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/2026/93xxx/CVE-2026-93216.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-93216",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 494438,
  "published_at": "2026-09-24T15:10:38.702+00:00"
}