arm64/mm: fix incorrect file_map_count for non-leaf pmd/pud

{
  "id": "ff5b4beb40429d8439ec3f3cab753beae68bbed7879e02cadff5f85e667a69df",
  "url": "https://osv.dev/vulnerability/CVE-2022-49778",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "arm64/mm: fix incorrect file_map_count for non-leaf pmd/pud",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: arm64/mm: fix incorrect file_map_count for non-leaf pmd/pud The page table check trigger BUG_ON() unexpectedly when collapse hugepage: ------------[ cut here ]------------ kernel BUG at mm/page_table_check.c:82! Internal error: Oops - BUG: 00000000f2000800 [#1] SMP Dumping ftrace buffer: (ftrace buffer empty) Modules linked in: CPU: 6 PID: 68 Comm: khugepaged Not tainted 6.1.0-rc3+ #750 Hardware name: linux,dummy-virt (DT) pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : page_table_check_clear.isra.0+0x258/0x3f0 lr : page_table_check_clear.isra.0+0x240/0x3f0 [...] Call trace: page_table_check_clear.isra.0+0x258/0x3f0 __page_table_check_pmd_clear+0xbc/0x108 pmdp_collapse_flush+0xb0/0x160 collapse_huge_page+0xa08/0x1080 hpage_collapse_scan_pmd+0xf30/0x1590 khugepaged_scan_mm_slot.constprop.0+0x52c/0xac8 khugepaged+0x338/0x518 kthread+0x278/0x2f8 ret_from_fork+0x10/0x20 [...] Since pmd_user_accessible_page() doesn't check if a pmd is leaf, it decrease file_map_count for a non-leaf pmd comes from collapse_huge_page(). and so trigger BUG_ON() unexpectedly. Fix this problem by using pmd_leaf() insteal of pmd_present() in pmd_user_accessible_page(). Moreover, use pud_leaf() for pud_user_accessible_page() too.",
    "evidence": "osv:CVE-2022-49778",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.0.10",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2022-49778",
      "aliases": [
        "CVE-2022-49778"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "42b2547137f5c974bb1bfd657c869fe96b96d86f"
                },
                {
                  "fixed": "2d458046df634088611d44fd77f45465e833ef78"
                },
                {
                  "fixed": "5b47348fc0b18a78c96f8474cc90b7525ad1bbfe"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2022-49778.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.19.0"
                },
                {
                  "fixed": "6.0.10"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2022-49778.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:42.679568471Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/2d458046df634088611d44fd77f45465e833ef78",
        "https://git.kernel.org/stable/c/5b47348fc0b18a78c96f8474cc90b7525ad1bbfe",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2022/49xxx/CVE-2022-49778.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2022-49778",
        "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/2022/49xxx/CVE-2022-49778.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2022-49778",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 510230,
  "published_at": "2025-05-01T14:09:13.828+00:00"
}