CVE-2025-39684 (GCVE-0-2025-39684)

Vulnerability from cvelistv5 – Published: 2025-09-05 17:20 – Updated: 2026-05-12 12:06
VLAI
Title
comedi: Fix use of uninitialized memory in do_insn_ioctl() and do_insnlist_ioctl()
Summary
In the Linux kernel, the following vulnerability has been resolved: comedi: Fix use of uninitialized memory in do_insn_ioctl() and do_insnlist_ioctl() syzbot reports a KMSAN kernel-infoleak in `do_insn_ioctl()`. A kernel buffer is allocated to hold `insn->n` samples (each of which is an `unsigned int`). For some instruction types, `insn->n` samples are copied back to user-space, unless an error code is being returned. The problem is that not all the instruction handlers that need to return data to userspace fill in the whole `insn->n` samples, so that there is an information leak. There is a similar syzbot report for `do_insnlist_ioctl()`, although it does not have a reproducer for it at the time of writing. One culprit is `insn_rw_emulate_bits()` which is used as the handler for `INSN_READ` or `INSN_WRITE` instructions for subdevices that do not have a specific handler for that instruction, but do have an `INSN_BITS` handler. For `INSN_READ` it only fills in at most 1 sample, so if `insn->n` is greater than 1, the remaining `insn->n - 1` samples copied to userspace will be uninitialized kernel data. Another culprit is `vm80xx_ai_insn_read()` in the "vm80xx" driver. It never returns an error, even if it fails to fill the buffer. Fix it in `do_insn_ioctl()` and `do_insnlist_ioctl()` by making sure that uninitialized parts of the allocated buffer are zeroed before handling each instruction. Thanks to Arnaud Lecomte for their fix to `do_insn_ioctl()`. That fix replaced the call to `kmalloc_array()` with `kcalloc()`, but it is not always necessary to clear the whole buffer.
Severity
5.5 (Medium)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6843 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: ed9eccbe8970f6eedc1b978c157caf1251a896d4 , < 868a1b68dcd9f2805bb86aa64862402f785d8c4a (git)
Affected: ed9eccbe8970f6eedc1b978c157caf1251a896d4 , < ff4a7c18799c7fe999fa56c5cf276e13866b8c1a (git)
Affected: ed9eccbe8970f6eedc1b978c157caf1251a896d4 , < d84f6e77ebe3359394df32ecd97e0d76a25283dc (git)
Affected: ed9eccbe8970f6eedc1b978c157caf1251a896d4 , < f3b0c9ec54736f3b8118f93a473d22e11ee65743 (git)
Affected: ed9eccbe8970f6eedc1b978c157caf1251a896d4 , < aecf0d557ddd95ce68193a5ee1dc4c87415ff08a (git)
Affected: ed9eccbe8970f6eedc1b978c157caf1251a896d4 , < 3cd212e895ca2d58963fdc6422502b10dd3966bb (git)
guessed Create a notification for this product.
Linux Linux Affected: 2.6.29
Unaffected: 0 , < 2.6.29 (semver)
Unaffected: 5.15.190 , ≤ 5.15.* (semver)
Unaffected: 6.1.149 , ≤ 6.1.* (semver)
Unaffected: 6.6.103 , ≤ 6.6.* (semver)
Unaffected: 6.12.44 , ≤ 6.12.* (semver)
Unaffected: 6.16.4 , ≤ 6.16.* (semver)
Unaffected: 6.17 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
Siemens SIMATIC CN 4100 Affected: 0 , < V5.0 (custom)
guessed Create a notification for this product.
Show details on NVD website
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            "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\ncomedi: Correcci\u00f3n del uso de memoria no inicializada en do_insn_ioctl() y do_insnlist_ioctl()\n\nsyzbot informa de una fuga de informaci\u00f3n del kernel (kernel-infoleak) de KMSAN en \u0027do_insn_ioctl()\u0027. Se asigna un b\u00fafer del kernel para contener \u0027insn-\u003en\u0027 muestras (cada una de las cuales es un \u0027unsigned int\u0027). Para algunos tipos de instrucci\u00f3n, se copian \u0027insn-\u003en\u0027 muestras de vuelta al espacio de usuario, a menos que se est\u00e9 devolviendo un c\u00f3digo de error. El problema es que no todos los gestores de instrucci\u00f3n que necesitan devolver datos al espacio de usuario rellenan la totalidad de las \u0027insn-\u003en\u0027 muestras, de modo que hay una fuga de informaci\u00f3n. Hay un informe similar de syzbot para \u0027do_insnlist_ioctl()\u0027, aunque no tiene un reproductor para ello en el momento de escribir esto.\n\nUn culpable es \u0027insn_rw_emulate_bits()\u0027 que se utiliza como gestor para instrucciones \u0027INSN_READ\u0027 o \u0027INSN_WRITE\u0027 para subdispositivos que no tienen un gestor espec\u00edfico para esa instrucci\u00f3n, pero s\u00ed tienen un gestor \u0027INSN_BITS\u0027. Para \u0027INSN_READ\u0027 solo rellena como m\u00e1ximo 1 muestra, as\u00ed que si \u0027insn-\u003en\u0027 es mayor que 1, las \u0027insn-\u003en - 1\u0027 muestras restantes copiadas al espacio de usuario ser\u00e1n datos del kernel no inicializados.\n\nOtro culpable es \u0027vm80xx_ai_insn_read()\u0027 en el controlador \u0027vm80xx\u0027. Nunca devuelve un error, incluso si falla al rellenar el b\u00fafer.\n\nSe corrige en \u0027do_insn_ioctl()\u0027 y \u0027do_insnlist_ioctl()\u0027 asegur\u00e1ndose de que las partes no inicializadas del b\u00fafer asignado se pongan a cero antes de manejar cada instrucci\u00f3n.\n\nGracias a Arnaud Lecomte por su correcci\u00f3n a \u0027do_insn_ioctl()\u0027. Esa correcci\u00f3n reemplaz\u00f3 la llamada a \u0027kmalloc_array()\u0027 por \u0027kcalloc()\u0027, pero no siempre es necesario limpiar todo el b\u00fafer."
          }
        ],
        "id": "CVE-2025-39684",
        "lastModified": "2026-10-19T21:10:00.160",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 5.5,
                "baseSeverity": "MEDIUM",
                "confidentialityImpact": "NONE",
                "integrityImpact": "NONE",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 1.8,
              "impactScore": 3.6,
              "source": "nvd@nist.gov",
              "type": "Primary"
            }
          ]
        },
        "published": "2025-09-05T18:15:45.020",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/3cd212e895ca2d58963fdc6422502b10dd3966bb"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/868a1b68dcd9f2805bb86aa64862402f785d8c4a"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/aecf0d557ddd95ce68193a5ee1dc4c87415ff08a"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/d84f6e77ebe3359394df32ecd97e0d76a25283dc"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/f3b0c9ec54736f3b8118f93a473d22e11ee65743"
          },
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
              "Patch"
            ],
            "url": "https://git.kernel.org/stable/c/ff4a7c18799c7fe999fa56c5cf276e13866b8c1a"
          },
          {
            "source": "af854a3a-2127-422b-91ae-364da2661108",
            "tags": [
              "Third Party Advisory"
            ],
            "url": "https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html"
          },
          {
            "source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e",
            "url": "https://cert-portal.siemens.com/productcert/html/ssa-032379.html"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Modified",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-908"
              }
            ],
            "source": "nvd@nist.gov",
            "type": "Primary"
          }
        ]
      }
    },
    "redhat_vex": {
      "aggregate_severity": "None",
      "current_release_date": "2026-06-30T10:29:04+00:00",
      "cve": "CVE-2025-39684",
      "id": "CVE-2025-39684",
      "initial_release_date": "2025-09-05T00:00:00+00:00",
      "product_status:known_not_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: comedi: Fix use of uninitialized memory in do_insn_ioctl() and do_insnlist_ioctl()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-39684.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-10-17T00:56:59Z",
      "cve": "CVE-2025-39684",
      "id": "CVE-2025-39684",
      "initial_release_date": "2025-09-08T23:22:51Z",
      "product_status:known_affected": "791",
      "product_status:recommended": "495",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2025-39684",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/2025/cve-2025-39684.json",
      "version": "60"
    }
  }
}



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