CVE-2025-40242 (GCVE-0-2025-40242)
Vulnerability from cvelistv5
Published
2025-12-04 15:31
Modified
2026-08-05 12:08
Severity ?
7.0 (High) - CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: gfs2: Fix unlikely race in gdlm_put_lock In gdlm_put_lock(), there is a small window of time in which the DFL_UNMOUNT flag has been set but the lockspace hasn't been released, yet. In that window, dlm may still call gdlm_ast() and gdlm_bast(). To prevent it from dereferencing freed glock objects, only free the glock if the lockspace has actually been released.
References
Impacted products
Vendor Product Version
Linux Linux Version: d1340f80f0b8066321b499a376780da00560e857
Version: d1340f80f0b8066321b499a376780da00560e857
Version: d1340f80f0b8066321b499a376780da00560e857
Version: d1340f80f0b8066321b499a376780da00560e857
Version: d1340f80f0b8066321b499a376780da00560e857
Version: 6aa628c45875e7b8cca81ed9447a12a0e8f3504a
Version: a97e75203733be0a4263a78fb7b29352be150c1c
Version: 3554b46204e67333e1fb8be0e93936fb08267c80
Version: 5cff77b9827a956d076168b56775aad23bce87e4
Version: 8deedce385d220f90e435f534d71d27526273515
Version: 2225a5cd2fbc2ef0e0f78e585db3844f60416a39
Version: 02e838963fdaa6ce8570b5389aecdc6cf1fb40b0
Version: 01eb3106f43335fdc02111358dae80a5c3fd324d
Version: 4.4.284   ≤
Version: 4.9.283   ≤
Version: 4.14.247   ≤
Version: 4.19.207   ≤
Version: 5.4.148   ≤
Version: 5.10.67   ≤
Version: 5.13.19   ≤
Version: 5.14.6   ≤
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{
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          "product": "Linux",
          "programFiles": [
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              "status": "unaffected",
              "version": "6.12.56",
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              "status": "unaffected",
              "version": "6.17.6",
              "versionType": "semver"
            },
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              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.18",
              "versionType": "original_commit_for_fix"
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      "cpeApplicability": [
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                  "vulnerable": true
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              ],
              "negate": false,
              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ngfs2: Fix unlikely race in gdlm_put_lock\n\nIn gdlm_put_lock(), there is a small window of time in which the\nDFL_UNMOUNT flag has been set but the lockspace hasn\u0027t been released,\nyet.  In that window, dlm may still call gdlm_ast() and gdlm_bast().\nTo prevent it from dereferencing freed glock objects, only free the\nglock if the lockspace has actually been released."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The window is opened by a local umount or a local filesystem withdraw, and the glock free is performed by local filesystem activity (inode eviction, glock shrinker, `glock_work_func`); the DLM bast that dereferences the freed object comes from an authenticated cluster peer on a private interconnect and cannot by itself create the dangling pointer. There is no network-facing service path into `gdlm_put_lock()`.\nAC:H - Exploitation requires winning a race whose opening the attacker does not control \u2014 `DFL_UNMOUNT` is set only by a root-driven umount or an error-driven withdraw \u2014 and additionally requires a DLM ast/bast for that exact resource to arrive after the free but before `dlm_release_lockspace()` completes, plus slab reuse after the RCU grace period. The author explicitly characterises it as an \"unlikely race\" in a \"small window of time\".\nPR:L - Once the teardown window is open (via administrator umount, cluster-manager failover, or a withdraw provoked by storage errors), an ordinary unprivileged user with access to the GFS2 mount drives the vulnerable side: normal file operations force glock disposal through `__gfs2_glock_put \u2192 lm_put_lock`, and creating inodes sprays `gfs2_glock_cachep` to groom the freed object. No capability check exists anywhere on that path.\nUI:N - The attacker only performs ordinary file operations on an already-mounted GFS2 filesystem; no victim must open a file, mount media, or take any deliberate action. The privileged unmount/withdraw is an environmental system state, accounted for in Attack Complexity rather than user interaction.\nS:U - The freed `struct gfs2_glock`, the DLM callback that writes into it, and any resulting corruption all live in the host kernel\u0027s own security authority. No hypervisor, IOMMU, or sandbox boundary is crossed.\nC:H - This is a use-after-free on a slab object whose contents the attacker can groom by reallocating glocks, and `gdlm_ast()` reads `gl-\u003egl_flags`, `gl-\u003egl_dstamp`, `gl-\u003egl_name.ln_type` and the `gl-\u003egl_name.ln_sbd` pointer out of the freed memory before the dead-lockref guard, using `ln_sbd` as a dereference target \u2014 giving an attacker-steerable kernel read primitive.\nI:H - Three distinct writes hit the freed object: DLM\u0027s `lksb-\u003esb_status`/`sb_flags` stores, `clear_bit(GLF_BLOCKING, \u0026gl-\u003egl_flags)`, and `gfs2_update_stats(\u0026gl-\u003egl_stats, ...)`; worse, `this_cpu_ptr(gl-\u003egl_name.ln_sbd-\u003esd_lkstats)` turns a groomed pointer in the freed object into the destination of a read-modify-write, and a surviving lockref check leads into `gfs2_glock_complete()` and `gl-\u003egl_ops` indirect calls \u2014 a control-flow hijack path.\nA:H - Dereferencing a freed glock from the DLM callback workqueue produces KASAN splats, oopses on garbage `ln_sbd`/`gl_ops` pointers, and `BUG()` in `gdlm_bast()` on an unrecognised mode, panicking the node. On a clustered filesystem, crashing the node also triggers fencing and cluster-wide recovery."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:08:46.271Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/5fdc1474e678eea1700aa266c0b7c2c96f81dd0d"
        },
        {
          "url": "https://git.kernel.org/stable/c/4913592a3358f6ec366b8346b733d5e2360b08e1"
        },
        {
          "url": "https://git.kernel.org/stable/c/279bde3bbb0ac0bad5c729dfa85983d75a5d7641"
        },
        {
          "url": "https://git.kernel.org/stable/c/64c61b4ac645222fa7b724cef616c1f862a72a40"
        },
        {
          "url": "https://git.kernel.org/stable/c/28c4d9bc0708956c1a736a9e49fee71b65deee81"
        }
      ],
      "title": "gfs2: Fix unlikely race in gdlm_put_lock",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-40242",
    "datePublished": "2025-12-04T15:31:31.497Z",
    "dateReserved": "2025-04-16T07:20:57.181Z",
    "dateUpdated": "2026-08-05T12:08:46.271Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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