CVE-2025-68807

Estado: AplazadaSin puntuar—

In the Linux kernel, the following vulnerability has been resolved:

block: fix race between wbt_enable_default and IO submission

When wbt_enable_default() is moved out of queue freezing in elevator_change(), it can cause the wbt inflight counter to become negative (-1), leading to hung tasks in the writeback path. Tasks get stuck in wbt_wait() because the counter is in an inconsistent state.

The issue occurs because wbt_enable_default() could race with IO submission, allowing the counter to be decremented before proper initialization. This manifests as:

rwb_enabled() checks the state, which can be updated exactly between wbt_wait() (rq_qos_throttle()) and wbt_track()(rq_qos_track()), then the inflight counter will become negative.

Leer descripción completaMostrar menos

Fix this by:

This ensures WBT is properly initialized before any IO can be submitted, preventing the counter from going negative.

Detalles técnicos trazas, registros y código del informe original

  rq_wait[0]:
    inflight:             -1
    has_waiters:        True

And results in hung task warnings like:
  task:kworker/u24:39 state:D stack:0 pid:14767
  Call Trace:
    rq_qos_wait+0xb4/0x150
    wbt_wait+0xa9/0x100
    __rq_qos_throttle+0x24/0x40
    blk_mq_submit_bio+0x672/0x7b0
    ...

1. Splitting wbt_enable_default() into:
   - __wbt_enable_default(): Returns true if wbt_init() should be called
   - wbt_enable_default(): Wrapper for existing callers (no init)
   - wbt_init_enable_default(): New function that checks and inits WBT

2. Using wbt_init_enable_default() in blk_register_queue() to ensure
   proper initialization during queue registration

3. Move wbt_init() out of wbt_enable_default() which is only for enabling
   disabled wbt from bfq and iocost, and wbt_init() isn't needed. Then the
   original lock warning can be avoided.

4. Removing the ELEVATOR_FLAG_ENABLE_WBT_ON_EXIT flag and its handling
   code since it's no longer needed

CVSS

NVD no ha asignado puntuación CVSS a esta CVE (habitual desde el cambio de política de abril de 2026).

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 0.18%
Percentil entre todas las CVEs puntuadas: 7
Fecha de la puntuación: 5/10/2026

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 (1)

⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.

Linux — Linux Kernel^AI

Referencias

JSON original (NVD)

Mostrar

{
  "id": "CVE-2025-68807",
  "cveTags": [],
  "metrics": {},
  "affected": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "affectedData": [
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "78c271344b6f64ce24c845e54903e09928cf2061",
              "lessThan": "f55201fb3becff6a903fd29f4d1147cc7e91eb0c",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "78c271344b6f64ce24c845e54903e09928cf2061",
              "lessThan": "9869d3a6fed381f3b98404e26e1afc75d680cbf9",
              "versionType": "git"
            }
          ],
          "programFiles": [
            "block/bfq-iosched.c",
            "block/blk-sysfs.c",
            "block/blk-wbt.c",
            "block/blk-wbt.h",
            "block/elevator.c",
            "block/elevator.h"
          ],
          "defaultStatus": "unaffected"
        },
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.16"
            },
            {
              "status": "unaffected",
              "version": "0",
              "lessThan": "6.16",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "6.18.3",
              "versionType": "semver",
              "lessThanOrEqual": "6.18.*"
            },
            {
              "status": "unaffected",
              "version": "6.19",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ],
          "programFiles": [
            "block/bfq-iosched.c",
            "block/blk-sysfs.c",
            "block/blk-wbt.c",
            "block/blk-wbt.h",
            "block/elevator.c",
            "block/elevator.h"
          ],
          "defaultStatus": "affected"
        }
      ]
    }
  ],
  "published": "2026-01-13T16:16:02.857",
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/9869d3a6fed381f3b98404e26e1afc75d680cbf9",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/f55201fb3becff6a903fd29f4d1147cc7e91eb0c",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "vulnStatus": "Deferred",
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nblock: fix race between wbt_enable_default and IO submission\n\nWhen wbt_enable_default() is moved out of queue freezing in elevator_change(),\nit can cause the wbt inflight counter to become negative (-1), leading to hung\ntasks in the writeback path. Tasks get stuck in wbt_wait() because the counter\nis in an inconsistent state.\n\nThe issue occurs because wbt_enable_default() could race with IO submission,\nallowing the counter to be decremented before proper initialization. This manifests\nas:\n\n  rq_wait[0]:\n    inflight:             -1\n    has_waiters:        True\n\nrwb_enabled() checks the state, which can be updated exactly between wbt_wait()\n(rq_qos_throttle()) and wbt_track()(rq_qos_track()), then the inflight counter\nwill become negative.\n\nAnd results in hung task warnings like:\n  task:kworker/u24:39 state:D stack:0 pid:14767\n  Call Trace:\n    rq_qos_wait+0xb4/0x150\n    wbt_wait+0xa9/0x100\n    __rq_qos_throttle+0x24/0x40\n    blk_mq_submit_bio+0x672/0x7b0\n    ...\n\nFix this by:\n\n1. Splitting wbt_enable_default() into:\n   - __wbt_enable_default(): Returns true if wbt_init() should be called\n   - wbt_enable_default(): Wrapper for existing callers (no init)\n   - wbt_init_enable_default(): New function that checks and inits WBT\n\n2. Using wbt_init_enable_default() in blk_register_queue() to ensure\n   proper initialization during queue registration\n\n3. Move wbt_init() out of wbt_enable_default() which is only for enabling\n   disabled wbt from bfq and iocost, and wbt_init() isn't needed. Then the\n   original lock warning can be avoided.\n\n4. Removing the ELEVATOR_FLAG_ENABLE_WBT_ON_EXIT flag and its handling\n   code since it's no longer needed\n\nThis ensures WBT is properly initialized before any IO can be submitted,\npreventing the counter from going negative."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nblock: corrige la condición de carrera entre wbt_enable_default y el envío de E/S\n\nCuando wbt_enable_default() se mueve fuera de la congelación de la cola en elevator_change(), puede hacer que el contador inflight de wbt se vuelva negativo (-1), lo que lleva a tareas colgadas en la ruta de writeback. Las tareas se quedan atascadas en wbt_wait() porque el contador está en un estado inconsistente.\n\nEl problema ocurre porque wbt_enable_default() podría competir con el envío de E/S, permitiendo que el contador se decremente antes de la inicialización adecuada. Esto se manifiesta como:\n\n  rq_wait[0]:\n    inflight:             -1\n    has_waiters:        True\n\nrwb_enabled() verifica el estado, que puede actualizarse exactamente entre wbt_wait() (rq_qos_throttle()) y wbt_track()(rq_qos_track()), entonces el contador inflight se volverá negativo.\n\nY resulta en advertencias de tareas colgadas como:\n  task:kworker/u24:39 state:D stack:0 pid:14767\n  Call Trace:\n    rq_qos_wait+0xb4/0x150\n    wbt_wait+0xa9/0x100\n    __rq_qos_throttle+0x24/0x40\n    blk_mq_submit_bio+0x672/0x7b0\n    ...\n\nEsto se soluciona mediante:\n\n1. Dividiendo wbt_enable_default() en:\n   - __wbt_enable_default(): Devuelve verdadero si se debe llamar a wbt_init()\n   - wbt_enable_default(): Envoltorio para las funciones que ya lo llaman (sin inicialización)\n   - wbt_init_enable_default(): Nueva función que verifica e inicializa WBT\n\n2. Usando wbt_init_enable_default() en blk_register_queue() para asegurar una inicialización adecuada durante el registro de la cola\n\n3. Moviendo wbt_init() fuera de wbt_enable_default(), que es solo para habilitar wbt deshabilitado de bfq e iocost, y wbt_init() no es necesario. Así se puede evitar la advertencia de bloqueo original.\n\n4. Eliminando la bandera ELEVATOR_FLAG_ENABLE_WBT_ON_EXIT y su código de manejo, ya que ya no es necesario\n\nEsto asegura que WBT se inicialice correctamente antes de que se pueda enviar cualquier E/S, evitando que el contador se vuelva negativo."
    }
  ],
  "lastModified": "2026-06-17T09:59:37.323",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}