erofs: ensure valid f_path for page cache sharing

{
  "id": "babb86bb7c39b2a88c3424e61262d7170abb0878163bf46de4311fc2d92755ea",
  "url": "https://osv.dev/vulnerability/CVE-2026-80697",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "erofs: ensure valid f_path for page cache sharing",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: erofs: ensure valid f_path for page cache sharing Previously, backing files for page cache sharing were set up with f_path left as NULL (only f_inode was valid). It worked, but a recent mincore fix relies on f_path.mnt and crashes (found by \"erofs/028\" on 7.2-rc4): BUG: kernel NULL pointer dereference, address: 0000000000000018 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: Oops: 0000 [#1] SMP PTI CPU: 3 UID: 0 PID: 675528 Comm: fincore Not tainted 7.2.0-rc4-00002-g[]-dirty #1 PREEMPT(lazy) Hardware name: Red Hat KVM, BIOS 1.16.0-4.al8 04/01/2014 RIP: 0010:__do_sys_mincore+0xc0/0x2c0 ... Specify valid paths using valid disconnected dentries together with erofs_ishare_mnt instead of leaving f_path empty, so they are more like real backing files in a pseudo filesystem and standard backing_file_open() can be used directly.",
    "evidence": "osv:CVE-2026-80697",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "7.1.8",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-80697",
      "aliases": [
        "CVE-2026-80697"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "5ef3208e3be50aa08b4e7a2832f34e16d42c08b3"
                },
                {
                  "fixed": "3879657c4ffd81b9a42cf575fc6cb60201032587"
                },
                {
                  "fixed": "96b2dbbe58a1ea5df8d29c2fe24b5f04715f4443"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-80697.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "7.0.0"
                },
                {
                  "fixed": "7.1.8"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-80697.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:50.614854253Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/3879657c4ffd81b9a42cf575fc6cb60201032587",
        "https://git.kernel.org/stable/c/96b2dbbe58a1ea5df8d29c2fe24b5f04715f4443",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80697.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-80697",
        "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/2026/80xxx/CVE-2026-80697.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-80697",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 519407,
  "published_at": "2026-08-28T06:53:02.236+00:00"
}