{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2025-39684",
  "modified": "2026-10-07T17:22:01Z",
  "upstream": [
    "CVE-2025-39684"
  ],
  "published": "2025-09-05T17:22:05Z",
  "summary": "comedi: Fix use of uninitialized memory in do_insn_ioctl() and do_insnlist_ioctl()",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ncomedi: Fix use of uninitialized memory in do_insn_ioctl() and do_insnlist_ioctl()\n\nsyzbot reports a KMSAN kernel-infoleak in `do_insn_ioctl()`.  A kernel\nbuffer is allocated to hold `insn->n` samples (each of which is an\n`unsigned int`).  For some instruction types, `insn->n` samples are\ncopied back to user-space, unless an error code is being returned.  The\nproblem is that not all the instruction handlers that need to return\ndata to userspace fill in the whole `insn->n` samples, so that there is\nan information leak.  There is a similar syzbot report for\n`do_insnlist_ioctl()`, although it does not have a reproducer for it at\nthe time of writing.\n\nOne culprit is `insn_rw_emulate_bits()` which is used as the handler for\n`INSN_READ` or `INSN_WRITE` instructions for subdevices that do not have\na specific handler for that instruction, but do have an `INSN_BITS`\nhandler.  For `INSN_READ` it only fills in at most 1 sample, so if\n`insn->n` is greater than 1, the remaining `insn->n - 1` samples copied\nto userspace will be uninitialized kernel data.\n\nAnother culprit is `vm80xx_ai_insn_read()` in the \"vm80xx\" driver.  It\nnever returns an error, even if it fails to fill the buffer.\n\nFix it in `do_insn_ioctl()` and `do_insnlist_ioctl()` by making sure\nthat uninitialized parts of the allocated buffer are zeroed before\nhandling each instruction.\n\nThanks to Arnaud Lecomte for their fix to `do_insn_ioctl()`.  That fix\nreplaced the call to `kmalloc_array()` with `kcalloc()`, but it is not\nalways necessary to clear the whole buffer.",
  "affected": [
    {
      "package": {
        "ecosystem": "Raspberry Pi OS:12",
        "name": "linux"
      },
      "versions": [
        "1:6.1.47-1+rpt4"
      ],
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-2712",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v6",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7l",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v8",
            "binary_version": "1:6.1.47-1+rpt4"
          }
        ]
      },
      "database_specific": {
        "per_version": {
          "1:6.1.47-1+rpt4": {
            "linux_commit": "655fc658a15ae7a6f37103754adb39ba52a9a14e",
            "upstream_version": "6.1.47",
            "assessment": "commit ancestry (strak rule)",
            "upstream_fixed": "6.1.149",
            "compiled_filter": false
          }
        }
      }
    }
  ],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2025-39684"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/868a1b68dcd9f2805bb86aa64862402f785d8c4a"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/ff4a7c18799c7fe999fa56c5cf276e13866b8c1a"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/d84f6e77ebe3359394df32ecd97e0d76a25283dc"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/f3b0c9ec54736f3b8118f93a473d22e11ee65743"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/aecf0d557ddd95ce68193a5ee1dc4c87415ff08a"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/3cd212e895ca2d58963fdc6422502b10dd3966bb"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-05-12T04:54:46Z"
  }
}