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comedi: Make insn_rw_emulate_bits() do insn->n samples

Type: advisorySources: OSV

In the Linux kernel, the following vulnerability has been resolved: comedi: Make insn_rw_emulate_bits() do insn->n samples The `insn_rw_emulate_bits()` function is used as a default handler for `INSN_READ` instructions for subdevices that have a handler for `INSN_BITS` but not for `INSN_READ`. Similarly, it is used as a default handler for `INSN_WRITE` instructions for subdevices that have a handler for `INSN_BITS` but not for `INSN_WRITE`. It works by emulating the `INSN_READ` or `INSN_WRITE` instruction handling with a constructed `INSN_BITS` instruction. However, `INSN_READ` and `INSN_WRITE` instructions are supposed to be able read or write multiple samples, indicated by the `insn->n` value, but `insn_rw_emulate_bits()` currently only handles a single sample. For `INSN_READ`, the comedi core will copy `insn->n` samples back to user-space. (That triggered KASAN kernel-infoleak errors when `insn->n` was greater than 1, but that is being fixed more generally elsewhere in the comedi core.) Make `insn_rw_emulate_bits()` either handle `insn->n` samples, or return an error, to conform to the general expectation for `INSN_READ` and `INSN_WRITE` handlers.

Products
Kernel
Affected versions
Not specified
Fixed versions
5.15.190, 6.1.149, 6.12.44, 6.16.4, 6.6.103
CVEs
CVE-2025-39686
Confirmed fixed CVEs
Not specified
Updated in this feed
2 Nov 2026, 20:24 UTC · Revision 1

Source evidence

comedi: Make insn_rw_emulate_bits() do insn->n samples

core-osv · Original source

Published 5 Sept 2025, 17:20 UTC

In the Linux kernel, the following vulnerability has been resolved: comedi: Make insn_rw_emulate_bits() do insn->n samples The `insn_rw_emulate_bits()` function is used as a default handler for `INSN_READ` instructions for subdevices that have a handler for `INSN_BITS` but not for `INSN_READ`. Similarly, it is used as a default handler for `INSN_WRITE` instructions for subdevices that have a handler for `INSN_BITS` but not for `INSN_WRITE`. It works by emulating the `INSN_READ` or `INSN_WRITE` instruction handling with a constructed `INSN_BITS` instruction. However, `INSN_READ` and `INSN_WRITE` instructions are supposed to be able read or write multiple samples, indicated by the `insn->n` value, but `insn_rw_emulate_bits()` currently only handles a single sample. For `INSN_READ`, the comedi core will copy `insn->n` samples back to user-space. (That triggered KASAN kernel-infoleak errors when `insn->n` was greater than 1, but that is being fixed more generally elsewhere in the comedi core.) Make `insn_rw_emulate_bits()` either handle `insn->n` samples, or return an error, to conform to the general expectation for `INSN_READ` and `INSN_WRITE` handlers.

osv:CVE-2025-39686

Kernel

Fixed versions: 5.15.190, 6.1.149, 6.6.103, 6.12.44, 6.16.4

Complete source record
{
  "id": "f278284323ee04c5f6fe71af9d87ee79d4c46b7922d9d5cdad1d623b0eb7868a",
  "url": "https://osv.dev/vulnerability/CVE-2025-39686",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "comedi: Make insn_rw_emulate_bits() do insn->n samples",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: comedi: Make insn_rw_emulate_bits() do insn->n samples The `insn_rw_emulate_bits()` function is used as a default handler for `INSN_READ` instructions for subdevices that have a handler for `INSN_BITS` but not for `INSN_READ`. Similarly, it is used as a default handler for `INSN_WRITE` instructions for subdevices that have a handler for `INSN_BITS` but not for `INSN_WRITE`. It works by emulating the `INSN_READ` or `INSN_WRITE` instruction handling with a constructed `INSN_BITS` instruction. However, `INSN_READ` and `INSN_WRITE` instructions are supposed to be able read or write multiple samples, indicated by the `insn->n` value, but `insn_rw_emulate_bits()` currently only handles a single sample. For `INSN_READ`, the comedi core will copy `insn->n` samples back to user-space. (That triggered KASAN kernel-infoleak errors when `insn->n` was greater than 1, but that is being fixed more generally elsewhere in the comedi core.) Make `insn_rw_emulate_bits()` either handle `insn->n` samples, or return an error, to conform to the general expectation for `INSN_READ` and `INSN_WRITE` handlers.",
    "evidence": "osv:CVE-2025-39686",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "5.15.190",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.1.149",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.103",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.44",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.16.4",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2025-39686",
      "aliases": [
        "CVE-2025-39686"
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "type": "GIT",
              "events": [
                {
                  "introduced": "ed9eccbe8970f6eedc1b978c157caf1251a896d4"
                },
                {
                  "fixed": "ab77e85bd3bc006ef40738f26f446a660813da44"
                },
                {
                  "fixed": "ae8bc1f07bcb31b8636420e03d1f9c3df6219a2b"
                },
                {
                  "fixed": "842f307a1d115b24f2bcb2415c4e344f11f55930"
                },
                {
                  "fixed": "92352ed2f9ac422181e381c2430c2d0dfb46faa0"
                },
                {
                  "fixed": "dc0a2f142d655700db43de90cb6abf141b73d908"
                },
                {
                  "fixed": "7afba9221f70d4cbce0f417c558879cba0eb5e66"
                }
              ]
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-39686.json"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "2.6.29"
                },
                {
                  "fixed": "5.15.190"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "5.16.0"
                },
                {
                  "fixed": "6.1.149"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.2.0"
                },
                {
                  "fixed": "6.6.103"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.7.0"
                },
                {
                  "fixed": "6.12.44"
                }
              ]
            },
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "6.13.0"
                },
                {
                  "fixed": "6.16.4"
                }
              ]
            }
          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-39686.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:23.374246128Z",
      "provider": "osv",
      "references": [
        "https://cert-portal.siemens.com/productcert/html/ssa-032379.html",
        "https://git.kernel.org/stable/c/7afba9221f70d4cbce0f417c558879cba0eb5e66",
        "https://git.kernel.org/stable/c/842f307a1d115b24f2bcb2415c4e344f11f55930",
        "https://git.kernel.org/stable/c/92352ed2f9ac422181e381c2430c2d0dfb46faa0",
        "https://git.kernel.org/stable/c/ab77e85bd3bc006ef40738f26f446a660813da44",
        "https://git.kernel.org/stable/c/ae8bc1f07bcb31b8636420e03d1f9c3df6219a2b",
        "https://git.kernel.org/stable/c/dc0a2f142d655700db43de90cb6abf141b73d908",
        "https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/39xxx/CVE-2025-39686.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2025-39686",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/39xxx/CVE-2025-39686.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2025-39686",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 489810,
  "published_at": "2025-09-05T17:20:53.071+00:00"
}