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CVE-2025-38480

Estado: AnalizadaMedia (5.5)—

In 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()`.

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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.

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

Tecnologías afectadas (2)

Debian — Debian LinuxLinux — Linux Kernel

CWE

Referencias

JSON original (NVD)

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      "value": "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's `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->n` 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->n` 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->n`, which is 0 in this case."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: comedi: Se corrige el uso de datos no inicializados en insn_rw_emulate_bits(). Para las instrucciones `INSN_READ` e `INSN_WRITE` de Comedi en subdispositivos \"digitales\" (tipos de subdispositivo `COMEDI_SUBD_DI`, `COMEDI_SUBD_DO` y `COMEDI_SUBD_DIO`), es común que el controlador del subdispositivo no tenga las funciones de controlador `insn_read` e `insn_write`, sino una función de controlador `insn_bits` para manejar las instrucciones `INSN_BITS` de Comedi. En ese caso, los punteros del controlador de función `insn_read` y/o `insn_write` del subdispositivo se configuran para apuntar a la función `insn_rw_emulate_bits()` mediante `__comedi_device_postconfig()`. Para `INSN_WRITE`, `insn_rw_emulate_bits()` actualmente asume que el valor `data[0]` proporcionado es una copia válida de la memoria del usuario. Al menos existirá porque `do_insnlist_ioctl()` y `do_insn_ioctl()` en \"comedi_fops.c\" garantizan la asignación de al menos `MIN_SAMPLES` (16) elementos. Sin embargo, si `insn->n` es 0 (lo cual es permitido para las instrucciones `INSN_READ` e `INSN_WRITE`, entonces `data[0]` puede contener datos no inicializados, y ciertamente contiene datos no válidos, posiblemente de una instrucción diferente en la matriz de instrucciones manejadas por `do_insnlist_ioctl()`. Esto dará como resultado que se escriba un valor incorrecto en el canal de salida digital (o en el canal de entrada/salida digital si se configura como una salida), y puede reflejarse en el estado guardado interno del canal. Arréglelo devolviendo 0 temprano si `insn->n` es 0, antes de llegar al código que accede a `data[0]`. Anteriormente, la función siempre devolvía 1 en caso de éxito, pero se supone que es el número de muestras de datos realmente leídas o escritas hasta `insn->n`, que es 0 en este caso."
    }
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  "lastModified": "2026-06-17T09:16:56.910",
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