CVE-2026-90260 (GCVE-0-2026-90260)

Vulnerability from cvelistv5 – Published: 2026-09-17 16:07 – Updated: 2026-09-18 17:54
VLAI
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.
Severity
7.1 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: aa6313e6ff2bfbf736a2739047bba355d8241584 , < 92484ad014f2e2b0e0e7bbc1610951e978cf557c (git)
Affected: aa6313e6ff2bfbf736a2739047bba355d8241584 , < 98e3747587f9f87f010d8d7e55786216249a94af (git)
Affected: aa6313e6ff2bfbf736a2739047bba355d8241584 , < db4b9eefc8ee0bcaeee4d5e6a7313905f6a2fe7c (git)
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Linux Linux Affected: 6.8
Unaffected: 0 , < 6.8 (semver)
Unaffected: 6.18.52 , ≤ 6.18.* (semver)
Unaffected: 7.2.6 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/btrfs/disk-io.c",
            "fs/btrfs/extent_io.c"
          ],
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          "vendor": "Linux",
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              "lessThan": "92484ad014f2e2b0e0e7bbc1610951e978cf557c",
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              "versionType": "git"
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              "versionType": "git"
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              "versionType": "git"
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            "fs/btrfs/extent_io.c"
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          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.8"
            },
            {
              "lessThan": "6.8",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "6.18.52",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "7.2.6",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix"
            }
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      ],
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.52",
                  "versionStartIncluding": "6.8",
                  "vulnerable": true
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                  "versionEndExcluding": "7.2.6",
                  "versionStartIncluding": "6.8",
                  "vulnerable": true
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                  "versionEndExcluding": "7.3-rc1",
                  "versionStartIncluding": "6.8",
                  "vulnerable": true
                }
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              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: zoned: don\u0027t clobber the extent buffer when zeroing it out\n\nOn a zoned filesystem a freed-but-still-dirty tree block is written out\nas zeros (EXTENT_BUFFER_ZONED_ZEROOUT) only to keep the zone write\npointer advancing. btree_csum_one_bio() implemented this by memzeroing\nthe extent buffer\u0027s own folios before submission.\n\nThat destroys the in-memory buffer while it may still be referenced. In\nparticular btrfs_free_tree_block() can run on it afterwards and reads\nthe header to add a delayed reference; once the header has been zeroed\nit frees bytenr 0 and corrupts the extent tree (the\nbtrfs_header_bytenr(buf) != 0 ASSERT in btrfs_free_tree_block(), or an\n\"unable to find ref\" abort). It is flaky and reproduces under fsstress,\ne.g. generic/461 and generic/013.\n\nWrite the zeros to disk from the shared zero page instead and leave the\nextent buffer content untouched, so any later reference - including the\ndelayed reference from btrfs_free_tree_block() - still sees a valid\nheader. end_bbio_meta_write() now clears writeback on the buffer\u0027s own\nfolios, as the bio no longer carries them."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The trigger is local VFS syscalls on a mounted zoned btrfs: unlink \u2192 btrfs_unlink() \u2192 btrfs_del_items() \u2192 btrfs_clear_buffer_dirty() sets EXTENT_BUFFER_ZONED_ZEROOUT, then fsync \u2192 btrfs_sync_file() \u2192 btree_writepages() \u2192 write_one_eb() \u2192 btree_csum_one_bio(). No network protocol carries the data that causes the clobber.\nAC:L - The attacker drives both sides: unlink/write churn that sets ZONED_ZEROOUT in btrfs_clear_buffer_dirty() while leaving DIRTY set, and fsync or btrfs_btree_balance_dirty() running btree_writepages(). lock_extent_buffer_for_io() drops the tree lock before the memzero, and btrfs_del_leaf() unlocks before btrfs_free_tree_block() reads the header.\nPR:L - btrfs_unlink() and btrfs_sync_file() have no capability check; an unprivileged user with write access on the already-mounted zoned volume can COW-free tree blocks and kick metadata writeback (fsync or the btrfs_btree_balance_dirty() at the end of btrfs_unlink()).\nUI:N - The attacker performs the unlink/write/fsync sequence themselves on files they can write; this is a runtime COW/writeback race on a legitimate zoned btrfs (reproduced by fsstress generic/461 and generic/013), not a crafted image a victim must mount.\nS:U - The clobbered extent-buffer folios and the bad delayed refs stay inside this mount\u0027s btrfs metadata in the host kernel; there is no KVM/Xen guest-to-host, IOMMU, or sandbox boundary crossing.\nC:N - btree_csum_one_bio() calls memzero_extent_buffer(eb, 0, eb-\u003elen), which memset_extent_buffer() restricts to that buffer\u0027s own folios via check_eb_range(); the overwrite is zeros, not an out-of-bounds read or kernel-pointer leak.\nI:H - After the header is zeroed, btrfs_free_tree_block() queues a BTRFS_DROP_DELAYED_REF with owning_root=btrfs_header_owner(buf)==0 and level=btrfs_header_level(buf)==0, so __btrfs_free_extent() applies a mismatched backref to the shared extent tree and corrupts metadata for every file on the volume.\nA:H - The mismatched delayed ref hits abort_and_dump() \u2192 btrfs_abort_transaction(-EUCLEAN) \u2192 __btrfs_handle_fs_error() \u2192 btrfs_set_sb_rdonly(), forcing the whole filesystem read-only; with CONFIG_BTRFS_ASSERT, ASSERT(btrfs_header_bytenr(buf) != 0) in btrfs_free_tree_block() panics."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-18T17:54:13.818Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/92484ad014f2e2b0e0e7bbc1610951e978cf557c"
        },
        {
          "url": "https://git.kernel.org/stable/c/98e3747587f9f87f010d8d7e55786216249a94af"
        },
        {
          "url": "https://git.kernel.org/stable/c/db4b9eefc8ee0bcaeee4d5e6a7313905f6a2fe7c"
        }
      ],
      "title": "btrfs: zoned: don\u0027t clobber the extent buffer when zeroing it out",
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        "engine": "bippy-1.2.0"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-90260",
    "datePublished": "2026-09-17T16:07:58.102Z",
    "dateReserved": "2026-09-11T19:38:34.796Z",
    "dateUpdated": "2026-09-18T17:54:13.818Z",
    "state": "PUBLISHED"
  },
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  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
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      "date": "2026-09-25",
      "epss": "0.00169",
      "percentile": "0.05503"
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                "product": "Linux",
                "programFiles": [
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                  "fs/btrfs/extent_io.c"
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        "cveTags": [],
        "descriptions": [
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            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: zoned: don\u0027t clobber the extent buffer when zeroing it out\n\nOn a zoned filesystem a freed-but-still-dirty tree block is written out\nas zeros (EXTENT_BUFFER_ZONED_ZEROOUT) only to keep the zone write\npointer advancing. btree_csum_one_bio() implemented this by memzeroing\nthe extent buffer\u0027s own folios before submission.\n\nThat destroys the in-memory buffer while it may still be referenced. In\nparticular btrfs_free_tree_block() can run on it afterwards and reads\nthe header to add a delayed reference; once the header has been zeroed\nit frees bytenr 0 and corrupts the extent tree (the\nbtrfs_header_bytenr(buf) != 0 ASSERT in btrfs_free_tree_block(), or an\n\"unable to find ref\" abort). It is flaky and reproduces under fsstress,\ne.g. generic/461 and generic/013.\n\nWrite the zeros to disk from the shared zero page instead and leave the\nextent buffer content untouched, so any later reference - including the\ndelayed reference from btrfs_free_tree_block() - still sees a valid\nheader. end_bbio_meta_write() now clears writeback on the buffer\u0027s own\nfolios, as the bio no longer carries them."
          }
        ],
        "id": "CVE-2026-90260",
        "lastModified": "2026-09-18T18:17:51.297",
        "metrics": {
          "cvssMetricV31": [
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              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 7.1,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "NONE",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H",
                "version": "3.1"
              },
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              "impactScore": 5.2,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
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        },
        "published": "2026-09-17T17:17:22.433",
        "references": [
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            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/92484ad014f2e2b0e0e7bbc1610951e978cf557c"
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
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    }
  }
}



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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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