GHSA-G4QG-7MGJ-P8V6
Vulnerability from github – Published: 2025-07-28 12:30 – Updated: 2026-01-07 18:30In the Linux kernel, the following vulnerability has been resolved:
comedi: Fix use of uninitialized data in insn_rw_emulate_bits()
For Comedi INSN_READ and INSN_WRITE instructions on "digital"
subdevices (subdevice types COMEDI_SUBD_DI, COMEDI_SUBD_DO, and
COMEDI_SUBD_DIO), it is common for the subdevice driver not to have
insn_read and insn_write handler functions, but to have an
insn_bits handler function for handling Comedi INSN_BITS
instructions. In that case, the subdevice's insn_read and/or
insn_write function handler pointers are set to point to the
insn_rw_emulate_bits() function by __comedi_device_postconfig().
For INSN_WRITE, insn_rw_emulate_bits() currently assumes that the
supplied data[0] value is a valid copy from user memory. It will at
least exist because do_insnlist_ioctl() and do_insn_ioctl() in
"comedi_fops.c" ensure at lease MIN_SAMPLES (16) elements are
allocated. However, if insn->n is 0 (which is allowable for
INSN_READ and INSN_WRITE instructions, then data[0] may contain
uninitialized data, and certainly contains invalid data, possibly from a
different instruction in the array of instructions handled by
do_insnlist_ioctl(). This will result in an incorrect value being
written to the digital output channel (or to the digital input/output
channel if configured as an output), and may be reflected in the
internal saved state of the channel.
Fix it by returning 0 early if insn->n is 0, before reaching the code
that accesses data[0]. Previously, the function always returned 1 on
success, but it is supposed to be the number of data samples actually
read or written up to insn->n, which is 0 in this case.
{
"affected": [],
"aliases": [
"CVE-2025-38480"
],
"database_specific": {
"cwe_ids": [
"CWE-908"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-07-28T12:15:29Z",
"severity": "MODERATE"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\ncomedi: Fix use of uninitialized data in insn_rw_emulate_bits()\n\nFor Comedi `INSN_READ` and `INSN_WRITE` instructions on \"digital\"\nsubdevices (subdevice types `COMEDI_SUBD_DI`, `COMEDI_SUBD_DO`, and\n`COMEDI_SUBD_DIO`), it is common for the subdevice driver not to have\n`insn_read` and `insn_write` handler functions, but to have an\n`insn_bits` handler function for handling Comedi `INSN_BITS`\ninstructions. In that case, the subdevice\u0027s `insn_read` and/or\n`insn_write` function handler pointers are set to point to the\n`insn_rw_emulate_bits()` function by `__comedi_device_postconfig()`.\n\nFor `INSN_WRITE`, `insn_rw_emulate_bits()` currently assumes that the\nsupplied `data[0]` value is a valid copy from user memory. It will at\nleast exist because `do_insnlist_ioctl()` and `do_insn_ioctl()` in\n\"comedi_fops.c\" ensure at lease `MIN_SAMPLES` (16) elements are\nallocated. However, if `insn-\u003en` is 0 (which is allowable for\n`INSN_READ` and `INSN_WRITE` instructions, then `data[0]` may contain\nuninitialized data, and certainly contains invalid data, possibly from a\ndifferent instruction in the array of instructions handled by\n`do_insnlist_ioctl()`. This will result in an incorrect value being\nwritten to the digital output channel (or to the digital input/output\nchannel if configured as an output), and may be reflected in the\ninternal saved state of the channel.\n\nFix it by returning 0 early if `insn-\u003en` is 0, before reaching the code\nthat accesses `data[0]`. Previously, the function always returned 1 on\nsuccess, but it is supposed to be the number of data samples actually\nread or written up to `insn-\u003en`, which is 0 in this case.",
"id": "GHSA-g4qg-7mgj-p8v6",
"modified": "2026-01-07T18:30:18Z",
"published": "2025-07-28T12:30:35Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-38480"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/10f9024a8c824a41827fff1fefefb314c98e2c88"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/16256d7efcf7acc9f39abe21522c4c6b77f67c00"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/2af1e7d389c2619219171d23f5b96dbcbb7f9656"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3050d197d6bc9ef128944a70210f42d2430b3000"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3ab55ffaaf75d0c7b68e332c1cdcc1b0e0044870"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/4c2981bf30401adfcdbfece4ab6f411f7c5875a1"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c53570e62b5b28bdb56bb563190227f8307817a5"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/e9cb26291d009243a4478a7ffb37b3a9175bfce9"
},
{
"type": "WEB",
"url": "https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html"
},
{
"type": "WEB",
"url": "https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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