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CVE-2025-39686

Full vulnerability record from the local CVENow database.

Description

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.

Severity
HIGH
CVSS score
7.8 (v3.1)
Vulnerability status
Modified
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2025-09-05 18:15:45.297000
Last modified
2026-10-19 21:10:00.160000
View original CVE JSON 
{
  "id": "CVE-2025-39686",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2025-09-05T18:15:45.297",
  "lastModified": "2026-10-19T21:10:00.160",
  "vulnStatus": "Modified",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ncomedi: Make insn_rw_emulate_bits() do insn->n samples\n\nThe `insn_rw_emulate_bits()` function is used as a default handler for\n`INSN_READ` instructions for subdevices that have a handler for\n`INSN_BITS` but not for `INSN_READ`.  Similarly, it is used as a default\nhandler for `INSN_WRITE` instructions for subdevices that have a handler\nfor `INSN_BITS` but not for `INSN_WRITE`. It works by emulating the\n`INSN_READ` or `INSN_WRITE` instruction handling with a constructed\n`INSN_BITS` instruction.  However, `INSN_READ` and `INSN_WRITE`\ninstructions are supposed to be able read or write multiple samples,\nindicated by the `insn->n` value, but `insn_rw_emulate_bits()` currently\nonly handles a single sample.  For `INSN_READ`, the comedi core will\ncopy `insn->n` samples back to user-space.  (That triggered KASAN\nkernel-infoleak errors when `insn->n` was greater than 1, but that is\nbeing fixed more generally elsewhere in the comedi core.)\n\nMake `insn_rw_emulate_bits()` either handle `insn->n` samples, or return\nan error, to conform to the general expectation for `INSN_READ` and\n`INSN_WRITE` handlers."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\ncomedi: Hacer que 'insn_rw_emulate_bits()' procese 'insn->n' muestras\n\nLa función 'insn_rw_emulate_bits()' se utiliza como gestor predeterminado para instrucciones 'INSN_READ' para subdispositivos que tienen un gestor para 'INSN_BITS' pero no para 'INSN_READ'. De manera similar, se utiliza como gestor predeterminado para instrucciones 'INSN_WRITE' para subdispositivos que tienen un gestor para 'INSN_BITS' pero no para 'INSN_WRITE'. Funciona emulando el manejo de instrucciones 'INSN_READ' o 'INSN_WRITE' con una instrucción 'INSN_BITS' construida. Sin embargo, las instrucciones 'INSN_READ' e 'INSN_WRITE' deberían poder leer o escribir múltiples muestras, indicado por el valor 'insn->n', pero 'insn_rw_emulate_bits()' actualmente solo maneja una única muestra. Para 'INSN_READ', el núcleo de comedi copiará 'insn->n' muestras de vuelta al espacio de usuario. (Eso desencadenó errores de fuga de información del kernel de KASAN cuando 'insn->n' era mayor que 1, pero eso se está corrigiendo de manera más general en otra parte del núcleo de comedi.)\n\nHacer que 'insn_rw_emulate_bits()' maneje 'insn->n' muestras, o devuelva un error, para ajustarse a la expectativa general para los gestores de 'INSN_READ' e 'INSN_WRITE'."
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          "vendor": "Siemens",
          "product": "SIMATIC CN 4100",
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          "scope": "UNCHANGED",
          "confidentialityImpact": "HIGH",
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  "weaknesses": [
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      "source": "[email protected]",
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      "description": [
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          "lang": "en",
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