iomap: avoid potential null folio->mapping deref during error reporting

{
  "id": "9baf96f867c6ebf02fe327e8048d01b54cdbfda316adc6205d00f4b28cacbaee",
  "url": "https://osv.dev/vulnerability/CVE-2026-53165",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "iomap: avoid potential null folio->mapping deref during error reporting",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: iomap: avoid potential null folio->mapping deref during error reporting When a buffered read fails, iomap_finish_folio_read() reports the error with fserror_report_io(folio->mapping->host, ...). This is called after ifs->read_bytes_pending has been decremented by the bytes attempted to be read. For a folio split across multiple read completions, the folio is only guaranteed to stay locked while read_bytes_pending > 0. Once iomap_finish_folio_read() decrements read_bytes_pending, another in-flight read can complete and end the read on the folio, which unlocks it. This allows truncate logic to run and detach the folio (set folio->mapping to NULL). The error reporting path then can dereference a NULL folio->mapping. As reported by Sam Sun, this is the race that can occur: CPU0: failed completion CPU1: final completion CPU2: truncate ----------------------- ---------------------- -------------- read_bytes_pending -= len finished = false /* preempted before fserror_report_io() */ read_bytes_pending -= len finished = true folio_end_read() truncate clears folio->mapping fserror_report_io( folio->mapping->host, ...) ^ NULL deref Fix this by reporting the error first before decrementing ifs->read_bytes_pending.",
    "evidence": "osv:CVE-2026-53165",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "7.0.13",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-53165",
      "aliases": [
        "CVE-2026-53165"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "a9d573ee88af980f14fdadb5c12bbf6a195fb3f1"
                },
                {
                  "fixed": "1ad453817a4077230d1ba88eb0868f05f824449a"
                },
                {
                  "fixed": "2eea7f44b9c8b42fd7d3a1a87c06a7cd1b99c327"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-53165.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "7.0.0"
                },
                {
                  "fixed": "7.0.13"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-53165.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:32.094139503Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/1ad453817a4077230d1ba88eb0868f05f824449a",
        "https://git.kernel.org/stable/c/2eea7f44b9c8b42fd7d3a1a87c06a7cd1b99c327",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/53xxx/CVE-2026-53165.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-53165",
        "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/2026/53xxx/CVE-2026-53165.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-53165",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 498848,
  "published_at": "2026-06-25T08:38:45.445+00:00"
}