CVE-2025-40233 (GCVE-0-2025-40233)
Vulnerability from cvelistv5
Published
2025-12-04 15:31
Modified
2026-08-05 12:08
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: ocfs2: clear extent cache after moving/defragmenting extents The extent map cache can become stale when extents are moved or defragmented, causing subsequent operations to see outdated extent flags. This triggers a BUG_ON in ocfs2_refcount_cal_cow_clusters(). The problem occurs when: 1. copy_file_range() creates a reflinked extent with OCFS2_EXT_REFCOUNTED 2. ioctl(FITRIM) triggers ocfs2_move_extents() 3. __ocfs2_move_extents_range() reads and caches the extent (flags=0x2) 4. ocfs2_move_extent()/ocfs2_defrag_extent() calls __ocfs2_move_extent() which clears OCFS2_EXT_REFCOUNTED flag on disk (flags=0x0) 5. The extent map cache is not invalidated after the move 6. Later write() operations read stale cached flags (0x2) but disk has updated flags (0x0), causing a mismatch 7. BUG_ON(!(rec->e_flags & OCFS2_EXT_REFCOUNTED)) triggers Fix by clearing the extent map cache after each extent move/defrag operation in __ocfs2_move_extents_range(). This ensures subsequent operations read fresh extent data from disk.
References
Impacted products
Vendor Product Version
Linux Linux Version: 53069d4e76954e2e63c1b3c501051c6fbcf7298c
Version: 53069d4e76954e2e63c1b3c501051c6fbcf7298c
Version: 53069d4e76954e2e63c1b3c501051c6fbcf7298c
Version: 53069d4e76954e2e63c1b3c501051c6fbcf7298c
Version: 53069d4e76954e2e63c1b3c501051c6fbcf7298c
Version: 53069d4e76954e2e63c1b3c501051c6fbcf7298c
Version: 53069d4e76954e2e63c1b3c501051c6fbcf7298c
Version: 53069d4e76954e2e63c1b3c501051c6fbcf7298c
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{
  "containers": {
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        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/ocfs2/move_extents.c"
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      "cpeApplicability": [
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              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nocfs2: clear extent cache after moving/defragmenting extents\n\nThe extent map cache can become stale when extents are moved or\ndefragmented, causing subsequent operations to see outdated extent flags. \nThis triggers a BUG_ON in ocfs2_refcount_cal_cow_clusters().\n\nThe problem occurs when:\n1. copy_file_range() creates a reflinked extent with OCFS2_EXT_REFCOUNTED\n2. ioctl(FITRIM) triggers ocfs2_move_extents()\n3. __ocfs2_move_extents_range() reads and caches the extent (flags=0x2)\n4. ocfs2_move_extent()/ocfs2_defrag_extent() calls __ocfs2_move_extent()\n   which clears OCFS2_EXT_REFCOUNTED flag on disk (flags=0x0)\n5. The extent map cache is not invalidated after the move\n6. Later write() operations read stale cached flags (0x2) but disk has\n   updated flags (0x0), causing a mismatch\n7. BUG_ON(!(rec-\u003ee_flags \u0026 OCFS2_EXT_REFCOUNTED)) triggers\n\nFix by clearing the extent map cache after each extent move/defrag\noperation in __ocfs2_move_extents_range().  This ensures subsequent\noperations read fresh extent data from disk."
        }
      ],
      "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 vulnerability is reached through the OCFS2_IOC_MOVE_EXT ioctl and a subsequent write()/read() on a local file descriptor, requiring local system access. No remote protocol handler is involved.\nAC:L - The trigger is a deterministic, fully attacker-controlled sequence (copy_file_range \u2192 OCFS2_IOC_MOVE_EXT \u2192 write) with no race window, no memory-layout dependency, and no reliance on any condition outside the attacker\u0027s control; syzbot reproduced it reliably.\nPR:L - OCFS2_IOC_MOVE_EXT has no capability check whatsoever (unlike FITRIM in the same switch which requires CAP_SYS_ADMIN); any unprivileged local user holding a writable fd on a regular file of a mounted ocfs2 volume can drive the whole sequence.\nUI:N - The attacker performs every step on its own file descriptor with no action by any other user; the ocfs2 mount is a pre-existing property of the deployment, not an action the attacker must induce.\nS:U - The corruption and crash are confined to the kernel and the filesystem\u0027s own on-disk data within the same security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - The stale extent-map entry retains the old physical cluster, which is freed to the global bitmap by the truncate-log flush at the end of the move, so later reads (O_DIRECT or buffered after cache eviction) resolve through the stale mapping and return the contents of clusters the allocator has since handed to other users\u0027 or root-owned files.\nI:H - The same stale cpos\u2192old_phys mapping is used for writes and writeback, so attacker-controlled data lands on physical clusters now owned by a different file, giving arbitrary on-disk corruption of files the attacker has no write permission to.\nA:H - BUG_ON(!(rec-\u003ee_flags \u0026 OCFS2_EXT_REFCOUNTED)) at fs/ocfs2/refcounttree.c:2683 oopses the task while it holds inode_lock, ip_alloc_sem and the ocfs2 DLM inode lock, permanently wedging the filesystem and blocking other cluster nodes; with panic_on_oops it is a full system panic."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:08:43.055Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/93166bc53c0e3587058327a4121daea34b4fecd5"
        },
        {
          "url": "https://git.kernel.org/stable/c/a7ee72286efba1d407c6f15a0528e43593fb7007"
        },
        {
          "url": "https://git.kernel.org/stable/c/93b1ab422f1966b71561158e1aedce4ec100f357"
        },
        {
          "url": "https://git.kernel.org/stable/c/e92af7737a94a729225d2a5d180eaaa77fe0bbc1"
        },
        {
          "url": "https://git.kernel.org/stable/c/aa6a21409dd6221bb268b56bb410e031c632ff9a"
        },
        {
          "url": "https://git.kernel.org/stable/c/bb69928ed578f881e68d26aaf1a8f6e7faab3b44"
        },
        {
          "url": "https://git.kernel.org/stable/c/a21750df2f6169af6e039a3bb4893d6c9564e48d"
        },
        {
          "url": "https://git.kernel.org/stable/c/78a63493f8e352296dbc7cb7b3f4973105e8679e"
        }
      ],
      "title": "ocfs2: clear extent cache after moving/defragmenting extents",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-40233",
    "datePublished": "2025-12-04T15:31:23.891Z",
    "dateReserved": "2025-04-16T07:20:57.180Z",
    "dateUpdated": "2026-08-05T12:08:43.055Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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