btrfs: zoned: don't clobber the extent buffer when zeroing it out

{
  "id": "ef8e53f5b5781e40ef2be1a72946427780fe887b99f760662ac576022c294572",
  "url": "https://osv.dev/vulnerability/CVE-2026-90260",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "btrfs: zoned: don't clobber the extent buffer when zeroing it out",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: btrfs: zoned: don't clobber the extent buffer when zeroing it out On a zoned filesystem a freed-but-still-dirty tree block is written out as zeros (EXTENT_BUFFER_ZONED_ZEROOUT) only to keep the zone write pointer advancing. btree_csum_one_bio() implemented this by memzeroing the extent buffer's own folios before submission. That destroys the in-memory buffer while it may still be referenced. In particular btrfs_free_tree_block() can run on it afterwards and reads the header to add a delayed reference; once the header has been zeroed it frees bytenr 0 and corrupts the extent tree (the btrfs_header_bytenr(buf) != 0 ASSERT in btrfs_free_tree_block(), or an \"unable to find ref\" abort). It is flaky and reproduces under fsstress, e.g. generic/461 and generic/013. Write the zeros to disk from the shared zero page instead and leave the extent buffer content untouched, so any later reference - including the delayed reference from btrfs_free_tree_block() - still sees a valid header. end_bbio_meta_write() now clears writeback on the buffer's own folios, as the bio no longer carries them.",
    "evidence": "osv:CVE-2026-90260",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.12.114",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.52",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.2.6",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-90260",
      "aliases": [
        "CVE-2026-90260"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "aa6313e6ff2bfbf736a2739047bba355d8241584"
                },
                {
                  "fixed": "efa5084d08030aa557fdefa3e4a73b2501b7d207"
                },
                {
                  "fixed": "92484ad014f2e2b0e0e7bbc1610951e978cf557c"
                },
                {
                  "fixed": "98e3747587f9f87f010d8d7e55786216249a94af"
                },
                {
                  "fixed": "db4b9eefc8ee0bcaeee4d5e6a7313905f6a2fe7c"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-90260.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.8.0"
                },
                {
                  "fixed": "6.12.114"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.18.52"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.19.0"
                },
                {
                  "fixed": "7.2.6"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-90260.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:25.296344471Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/92484ad014f2e2b0e0e7bbc1610951e978cf557c",
        "https://git.kernel.org/stable/c/98e3747587f9f87f010d8d7e55786216249a94af",
        "https://git.kernel.org/stable/c/db4b9eefc8ee0bcaeee4d5e6a7313905f6a2fe7c",
        "https://git.kernel.org/stable/c/efa5084d08030aa557fdefa3e4a73b2501b7d207",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/90xxx/CVE-2026-90260.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-90260",
        "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/2026/90xxx/CVE-2026-90260.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-90260",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 492081,
  "published_at": "2026-09-17T16:07:58.102+00:00"
}