CVE-2025-39992 (GCVE-0-2025-39992)

Vulnerability from cvelistv5 – Published: 2025-10-15 07:58 – Updated: 2026-05-11 21:40
VLAI
Title
mm: swap: check for stable address space before operating on the VMA
Summary
In the Linux kernel, the following vulnerability has been resolved: mm: swap: check for stable address space before operating on the VMA It is possible to hit a zero entry while traversing the vmas in unuse_mm() called from swapoff path and accessing it causes the OOPS: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000446--> Loading the memory from offset 0x40 on the XA_ZERO_ENTRY as address. Mem abort info: ESR = 0x0000000096000005 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 FSC = 0x05: level 1 translation fault The issue is manifested from the below race between the fork() on a process and swapoff: fork(dup_mmap()) swapoff(unuse_mm) --------------- ----------------- 1) Identical mtree is built using __mt_dup(). 2) copy_pte_range()--> copy_nonpresent_pte(): The dst mm is added into the mmlist to be visible to the swapoff operation. 3) Fatal signal is sent to the parent process(which is the current during the fork) thus skip the duplication of the vmas and mark the vma range with XA_ZERO_ENTRY as a marker for this process that helps during exit_mmap(). 4) swapoff is tried on the 'mm' added to the 'mmlist' as part of the 2. 5) unuse_mm(), that iterates through the vma's of this 'mm' will hit the non-NULL zero entry and operating on this zero entry as a vma is resulting into the oops. The proper fix would be around not exposing this partially-valid tree to others when droping the mmap lock, which is being solved with [1]. A simpler solution would be checking for MMF_UNSTABLE, as it is set if mm_struct is not fully initialized in dup_mmap(). Thanks to Liam/Lorenzo/David for all the suggestions in fixing this issue.
Severity
No CVSS data available.
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 7063 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: d2406291483775ecddaee929231a39c70c08fda2 , < 4e5f060d7347466f77aaff1c0d5a6c4f1fb217ac (git)
Affected: d2406291483775ecddaee929231a39c70c08fda2 , < 9cddad3b26dac830407d2d3c0de5205ff6d6dda0 (git)
Affected: d2406291483775ecddaee929231a39c70c08fda2 , < e4e99d69b8b8295c501b2eef89e13306b738b667 (git)
Affected: d2406291483775ecddaee929231a39c70c08fda2 , < 1367da7eb875d01102d2ed18654b24d261ff5393 (git)
guessed Create a notification for this product.
Linux Linux Affected: 6.8
Unaffected: 0 , < 6.8 (semver)
Unaffected: 6.12.51 , ≤ 6.12.* (semver)
Unaffected: 6.16.11 , ≤ 6.16.* (semver)
Unaffected: 6.17.1 , ≤ 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\nmm: swap: check for stable address space before operating on the VMA\n\nIt is possible to hit a zero entry while traversing the vmas in unuse_mm()\ncalled from swapoff path and accessing it causes the OOPS:\n\nUnable to handle kernel NULL pointer dereference at virtual address\n0000000000000446--\u003e Loading the memory from offset 0x40 on the\nXA_ZERO_ENTRY as address.\nMem abort info:\n  ESR = 0x0000000096000005\n  EC = 0x25: DABT (current EL), IL = 32 bits\n  SET = 0, FnV = 0\n  EA = 0, S1PTW = 0\n  FSC = 0x05: level 1 translation fault\n\nThe issue is manifested from the below race between the fork() on a\nprocess and swapoff:\nfork(dup_mmap())\t\t\tswapoff(unuse_mm)\n---------------                         -----------------\n1) Identical mtree is built using\n   __mt_dup().\n\n2) copy_pte_range()--\u003e\n\tcopy_nonpresent_pte():\n       The dst mm is added into the\n    mmlist to be visible to the\n    swapoff operation.\n\n3) Fatal signal is sent to the parent\nprocess(which is the current during the\nfork) thus skip the duplication of the\nvmas and mark the vma range with\nXA_ZERO_ENTRY as a marker for this process\nthat helps during exit_mmap().\n\n\t\t\t\t     4) swapoff is tried on the\n\t\t\t\t\t\u0027mm\u0027 added to the \u0027mmlist\u0027 as\n\t\t\t\t\tpart of the 2.\n\n\t\t\t\t     5) unuse_mm(), that iterates\n\t\t\t\t\tthrough the vma\u0027s of this \u0027mm\u0027\n\t\t\t\t\twill hit the non-NULL zero entry\n\t\t\t\t\tand operating on this zero entry\n\t\t\t\t\tas a vma is resulting into the\n\t\t\t\t\toops.\n\nThe proper fix would be around not exposing this partially-valid tree to\nothers when droping the mmap lock, which is being solved with [1].  A\nsimpler solution would be checking for MMF_UNSTABLE, as it is set if\nmm_struct is not fully initialized in dup_mmap().\n\nThanks to Liam/Lorenzo/David for all the suggestions in fixing this\nissue."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-11T21:40:22.858Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/4e5f060d7347466f77aaff1c0d5a6c4f1fb217ac"
        },
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          "url": "https://git.kernel.org/stable/c/9cddad3b26dac830407d2d3c0de5205ff6d6dda0"
        },
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          "url": "https://git.kernel.org/stable/c/e4e99d69b8b8295c501b2eef89e13306b738b667"
        },
        {
          "url": "https://git.kernel.org/stable/c/1367da7eb875d01102d2ed18654b24d261ff5393"
        }
      ],
      "title": "mm: swap: check for stable address space before operating on the VMA",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2025-39992",
    "datePublished": "2025-10-15T07:58:17.927Z",
    "dateReserved": "2025-04-16T07:20:57.150Z",
    "dateUpdated": "2026-05-11T21:40:22.858Z",
    "state": "PUBLISHED"
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      "date": "2026-10-27",
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      "percentile": "0.09874"
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                "programFiles": [
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                "vendor": "Linux",
                "versions": [
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                    "version": "6.8"
                  },
                  {
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                    "versionType": "semver"
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                    "version": "6.12.51",
                    "versionType": "semver"
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                  {
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        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm: swap: check for stable address space before operating on the VMA\n\nIt is possible to hit a zero entry while traversing the vmas in unuse_mm()\ncalled from swapoff path and accessing it causes the OOPS:\n\nUnable to handle kernel NULL pointer dereference at virtual address\n0000000000000446--\u003e Loading the memory from offset 0x40 on the\nXA_ZERO_ENTRY as address.\nMem abort info:\n  ESR = 0x0000000096000005\n  EC = 0x25: DABT (current EL), IL = 32 bits\n  SET = 0, FnV = 0\n  EA = 0, S1PTW = 0\n  FSC = 0x05: level 1 translation fault\n\nThe issue is manifested from the below race between the fork() on a\nprocess and swapoff:\nfork(dup_mmap())\t\t\tswapoff(unuse_mm)\n---------------                         -----------------\n1) Identical mtree is built using\n   __mt_dup().\n\n2) copy_pte_range()--\u003e\n\tcopy_nonpresent_pte():\n       The dst mm is added into the\n    mmlist to be visible to the\n    swapoff operation.\n\n3) Fatal signal is sent to the parent\nprocess(which is the current during the\nfork) thus skip the duplication of the\nvmas and mark the vma range with\nXA_ZERO_ENTRY as a marker for this process\nthat helps during exit_mmap().\n\n\t\t\t\t     4) swapoff is tried on the\n\t\t\t\t\t\u0027mm\u0027 added to the \u0027mmlist\u0027 as\n\t\t\t\t\tpart of the 2.\n\n\t\t\t\t     5) unuse_mm(), that iterates\n\t\t\t\t\tthrough the vma\u0027s of this \u0027mm\u0027\n\t\t\t\t\twill hit the non-NULL zero entry\n\t\t\t\t\tand operating on this zero entry\n\t\t\t\t\tas a vma is resulting into the\n\t\t\t\t\toops.\n\nThe proper fix would be around not exposing this partially-valid tree to\nothers when droping the mmap lock, which is being solved with [1].  A\nsimpler solution would be checking for MMF_UNSTABLE, as it is set if\nmm_struct is not fully initialized in dup_mmap().\n\nThanks to Liam/Lorenzo/David for all the suggestions in fixing this\nissue."
          },
          {
            "lang": "es",
            "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nmm: swap: verificar el espacio de direcciones estable antes de operar en el VMA\n\nEs posible encontrar una entrada cero mientras se recorren los vmas en unuse_mm() llamada desde la ruta de swapoff y acceder a ella causa el OOPS:\n\nNo se puede manejar la desreferencia de puntero NULL del kernel en la direcci\u00f3n virtual 0000000000000446--\u003e Cargando la memoria desde el desplazamiento 0x40 en la XA_ZERO_ENTRY como direcci\u00f3n.\nInformaci\u00f3n de aborto de memoria:\n  ESR = 0x0000000096000005\n  EC = 0x25: DABT (EL actual), IL = 32 bits\n  SET = 0, FnV = 0\n  EA = 0, S1PTW = 0\n  FSC = 0x05: fallo de traducci\u00f3n de nivel 1\n\nEl problema se manifiesta a partir de la siguiente condici\u00f3n de carrera entre el fork() en un proceso y swapoff:\nfork(dup_mmap())\t\t\tswapoff(unuse_mm)\n---------------                         -----------------\n1) Se construye un mtree id\u00e9ntico\n   usando __mt_dup().\n\n2) copy_pte_range()--\u003e\n\tcopy_nonpresent_pte():\n       El mm de destino se a\u00f1ade a la\n    mmlist para ser visible para la\n    operaci\u00f3n de swapoff.\n\n3) Se env\u00eda una se\u00f1al fatal al proceso\npadre (que es el actual durante el\nfork), lo que omite la duplicaci\u00f3n de los\nvmas y marca el rango de vma con\nXA_ZERO_ENTRY como un marcador para este proceso\nque ayuda durante exit_mmap().\n\n\t\t\t\t     4) Se intenta swapoff en el\n\t\t\t\t\t\u0027mm\u0027 a\u00f1adido a la \u0027mmlist\u0027 como\n\t\t\t\t\tparte del punto 2.\n\n\t\t\t\t     5) unuse_mm(), que itera\n\t\t\t\t\ta trav\u00e9s de los vma\u0027s de este \u0027mm\u0027\n\t\t\t\t\tencontrar\u00e1 la entrada cero no-NULL\n\t\t\t\t\ty operar en esta entrada cero\n\t\t\t\t\tcomo un vma resulta en el\n\t\t\t\t\toops.\n\nLa soluci\u00f3n adecuada ser\u00eda no exponer este \u00e1rbol parcialmente v\u00e1lido a otros al liberar el bloqueo de mmap, lo cual se est\u00e1 resolviendo con [1]. Una soluci\u00f3n m\u00e1s simple ser\u00eda verificar MMF_UNSTABLE, ya que se establece si mm_struct no est\u00e1 completamente inicializado en dup_mmap().\n\nGracias a Liam/Lorenzo/David por todas las sugerencias para solucionar este problema."
          }
        ],
        "id": "CVE-2025-39992",
        "lastModified": "2026-10-19T21:10:00.160",
        "metrics": {},
        "published": "2025-10-15T08:15:37.317",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/1367da7eb875d01102d2ed18654b24d261ff5393"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/4e5f060d7347466f77aaff1c0d5a6c4f1fb217ac"
          },
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            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/9cddad3b26dac830407d2d3c0de5205ff6d6dda0"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/e4e99d69b8b8295c501b2eef89e13306b738b667"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Deferred"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-06-30T01:28:33+00:00",
      "cve": "CVE-2025-39992",
      "id": "CVE-2025-39992",
      "initial_release_date": "2025-10-15T00:00:00+00:00",
      "product_status:known_affected": "198",
      "product_status:known_not_affected": "76",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: mm: swap: check for stable address space before operating on the VMA",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-39992.json",
      "version": "3"
    }
  }
}



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