CVE-2026-63812 (GCVE-0-2026-63812)
Vulnerability from cvelistv5
Published
2026-07-19 12:02
Modified
2026-10-30 12:27
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: f2fs: fix incorrect FI_NO_EXTENT handling in __destroy_extent_node() When __destroy_extent_node() sets the inode flag FI_NO_EXTENT, it does not reset the length of the largest extent to 0 and update the inode folio. Since modifications to the extent tree are disallowed afterward, the cached largest extent may become stale. This can trigger the following error in xfstests generic/388: F2FS-fs (dm-0): sanity_check_extent_cache: inode (ino=1761) extent info [220057, 57, 6] is incorrect, run fsck to fix In the f2fs_drop_inode path, __destroy_extent_node() does not need to guarantee that et->node_cnt is 0, because concurrency with writeback is expected in this path, and writeback may update the extent cache. This patch reverts commit ed78aeebef05 ("f2fs: fix node_cnt race between extent node destroy and writeback"), and remove the unnecessary zero check of et->node_cnt.
References
Impacted products
Vendor Product Version
Linux Linux Version: 42dd1c91f993431d0b399502479d00e6ad1bca71
Version: ab1eaf9d5c99042f5b0243bf67a06283a4c0757f
Version: b0e4395870eb3441ddc959f6710b5f6ca61aff26
Version: ed78aeebef05212ef7dca93bd931e4eff67c113f
Version: ed78aeebef05212ef7dca93bd931e4eff67c113f
Version: b00e6950da9c0e4986f6e93c875d2b9184bdb220
Version: 0559a0e962aacbb47519e26ee663be04b72dcb92
Version: 6.6.140   ≤
Version: 6.12.88   ≤
Version: 6.18.30   ≤
Version: 6.1.191   ≤
Version: 7.0.7   ≤
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{
  "containers": {
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        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/f2fs/extent_cache.c"
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          "vendor": "Linux",
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              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
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          "nodes": [
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: fix incorrect FI_NO_EXTENT handling in __destroy_extent_node()\n\nWhen __destroy_extent_node() sets the inode flag FI_NO_EXTENT, it does\nnot reset the length of the largest extent to 0 and update the inode\nfolio. Since modifications to the extent tree are disallowed afterward,\nthe cached largest extent may become stale. This can trigger the\nfollowing error in xfstests generic/388:\n\nF2FS-fs (dm-0): sanity_check_extent_cache: inode (ino=1761) extent info [220057, 57, 6] is incorrect, run fsck to fix\n\nIn the f2fs_drop_inode path, __destroy_extent_node() does not need to\nguarantee that et-\u003enode_cnt is 0, because concurrency with writeback\nis expected in this path, and writeback may update the extent cache.\n\nThis patch reverts commit ed78aeebef05 (\"f2fs: fix node_cnt race between\nextent node destroy and writeback\"), and remove the unnecessary zero\ncheck of et-\u003enode_cnt."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The bug is reached only through local VFS filesystem activity (write, unlink, concurrent writeback) on an F2FS mount, most severely on Android/embedded userdata partitions where F2FS is the default local filesystem.\nAC:L - An attacker can reliably orchestrate the inode-eviction/writeback race by unlinking files while writeback is in progress on the same inode, controlling both sides of the concurrency window.\nPR:L - Triggering the race requires only unprivileged write access to files on a mounted F2FS filesystem (e.g., creating, writing, and unlinking files in one\u0027s own directory on Android /data), not real root or CAP_SYS_ADMIN.\nUI:N - Exploitation requires no action from a separate victim; the attacker drives the file I/O and unlink operations that provoke the stale extent-cache state.\nS:U - Impact is confined to kernel/filesystem integrity on the affected host; there is no cross-security-authority boundary such as VM escape or container-to-host breakout.\nC:H - Stale largest-extent metadata persisted to the on-disk inode can cause subsequent reads (after inode reload or inode-number reuse) to map logical file offsets to wrong physical blocks, disclosing data from other files or freed blocks.\nI:H - Incorrect on-disk extent metadata corrupts the inode-to-block mapping and can cause wrong data blocks to be associated with a file, constituting exploitable filesystem metadata corruption with integrity impact beyond a simple crash.\nA:H - The stale cache triggers sanity_check_extent_cache failures (as seen in xfstests generic/388), f2fs_handle_error(ERROR_CORRUPTED_INODE), and potential kernel BUG_ON via f2fs_bug_on when CONFIG_F2FS_CHECK_FS is enabled, all causing denial of filesystem or kernel service."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-30T12:27:08.582Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/7e4d8f98be63f98856a5176b9188dada6e7ba9ee"
        },
        {
          "url": "https://git.kernel.org/stable/c/58a5deb220bcac4c73bf58954c0845644c997487"
        },
        {
          "url": "https://git.kernel.org/stable/c/20190e498057997532c7f186d081011f18e0a462"
        },
        {
          "url": "https://git.kernel.org/stable/c/edf12cbeeeabe799bd2ee21fdb5c336cce6fbad7"
        },
        {
          "url": "https://git.kernel.org/stable/c/1f70ddb28a3c71df124da5fa4040c808116d6bb9"
        }
      ],
      "title": "f2fs: fix incorrect FI_NO_EXTENT handling in __destroy_extent_node()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-63812",
    "datePublished": "2026-07-19T12:02:13.606Z",
    "dateReserved": "2026-07-19T07:54:57.013Z",
    "dateUpdated": "2026-10-30T12:27:08.582Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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