CVE-2025-40242 (GCVE-0-2025-40242)

Vulnerability from cvelistv5 – Published: 2025-12-04 15:31 – Updated: 2026-10-15 22:02
VLAI
Title
gfs2: Fix unlikely race in gdlm_put_lock
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.
Severity
7 (High)
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-15 21:58 UTC
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 7061 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: d1340f80f0b8066321b499a376780da00560e857 , < 5fdc1474e678eea1700aa266c0b7c2c96f81dd0d (git)
Affected: d1340f80f0b8066321b499a376780da00560e857 , < 4913592a3358f6ec366b8346b733d5e2360b08e1 (git)
Affected: d1340f80f0b8066321b499a376780da00560e857 , < 279bde3bbb0ac0bad5c729dfa85983d75a5d7641 (git)
Affected: d1340f80f0b8066321b499a376780da00560e857 , < 64c61b4ac645222fa7b724cef616c1f862a72a40 (git)
Affected: d1340f80f0b8066321b499a376780da00560e857 , < 28c4d9bc0708956c1a736a9e49fee71b65deee81 (git)
Affected: 6aa628c45875e7b8cca81ed9447a12a0e8f3504a (git)
Affected: a97e75203733be0a4263a78fb7b29352be150c1c (git)
Affected: 3554b46204e67333e1fb8be0e93936fb08267c80 (git)
Affected: 5cff77b9827a956d076168b56775aad23bce87e4 (git)
Affected: 8deedce385d220f90e435f534d71d27526273515 (git)
Affected: 2225a5cd2fbc2ef0e0f78e585db3844f60416a39 (git)
Affected: 02e838963fdaa6ce8570b5389aecdc6cf1fb40b0 (git)
Affected: 01eb3106f43335fdc02111358dae80a5c3fd324d (git)
Affected: 4.4.284 , < 4.5 (semver)
Affected: 4.9.283 , < 4.10 (semver)
Affected: 4.14.247 , < 4.15 (semver)
Affected: 4.19.207 , < 4.20 (semver)
Affected: 5.4.148 , < 5.5 (semver)
Affected: 5.10.67 , < 5.11 (semver)
Affected: 5.13.19 , < 5.14 (semver)
Affected: 5.14.6 , < 5.15 (semver)
guessed Create a notification for this product.
Linux Linux Affected: 5.15
Unaffected: 0 , < 5.15 (semver)
Unaffected: 6.1.168 , ≤ 6.1.* (semver)
Unaffected: 6.6.131 , ≤ 6.6.* (semver)
Unaffected: 6.12.56 , ≤ 6.12.* (semver)
Unaffected: 6.17.6 , ≤ 6.17.* (semver)
Unaffected: 6.18 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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          "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."
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              "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."
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    "dateReserved": "2025-04-16T07:20:57.181Z",
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    "state": "PUBLISHED"
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            "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."
          },
          {
            "lang": "es",
            "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\ngfs2: Correcci\u00f3n de una condici\u00f3n de carrera improbable en gdlm_put_lock\n\nEn gdlm_put_lock(), existe una peque\u00f1a ventana de tiempo en la que la bandera DFL_UNMOUNT ha sido establecida, pero el lockspace a\u00fan no ha sido liberado. En esa ventana, dlm a\u00fan puede llamar a gdlm_ast() y gdlm_bast(). Para evitar que desreferencie objetos glock liberados, solo se debe liberar el glock si el lockspace ha sido realmente liberado."
          }
        ],
        "id": "CVE-2025-40242",
        "lastModified": "2026-10-19T19:10:00.130",
        "metrics": {
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                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
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      "product_status:known_affected": "150",
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      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: gfs2: Fix unlikely race in gdlm_put_lock",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-40242.json",
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              "shortName": "CISA-ADP"
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            "title": "CISA ADP Vulnrichment"
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              "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."
            }
          ],
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                "baseSeverity": "HIGH",
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                "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."
                }
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            "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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        "dateReserved": "2025-04-16T07:20:57.181Z",
        "dateUpdated": "2026-10-15T22:02:41.268Z",
        "state": "PUBLISHED"
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  }
}



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