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CVE-2026-89732

Estado: RecibidaSin puntuar—

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

usb: gadget: f_fs: Prevent deadlock during ep0 read loop

Currently, ffs_ep0_read() holds ffs->mutex when it prepares to go to sleep waiting for an event. When no setup events are pending, it calls wait_event_interruptible_exclusive_locked_irq() with the mutex still held. The wait macro deliberately drops the waitqueue spinlock before sleeping but does not drop the mutex.

If a userspace daemon is polling ep0 via read() and the gadget is asynchronously torn down via configfs (e.g., echo "" > UDC), a deadlock can occur:

To fix this, we drop both the waitqueue spinlock and ffs->mutex before going to sleep, and use wait_event_interruptible_exclusive() instead.

Leer descripción completaMostrar menos

Upon waking up, we jump back to the `retry` label to safely reacquire the mutex and re-evaluate the state machine. By not sleeping with ffs->mutex held, we natively decouple gadget teardowns (which require the mutex) from userspace polling.

Detalles técnicos trazas, registros y código del informe original
1. The configfs teardown calls functionfs_unbind(), which queues a
   FUNCTIONFS_UNBIND event.
2. The daemon wakes up, consumes the event, and drops the mutex.
3. However, if the daemon loops and immediately issues another read()
   before exiting, it reacquires ffs->mutex and again goes into an
   interruptible sleep.
4. Meanwhile, functionfs_unbind() continues execution and attempts to
   acquire ffs->mutex to tear down ep0req.
5. The kernel deadlocks because the configfs thread is stuck in an
   uninterruptible sleep waiting for the mutex, while the userspace
   daemon is in an interruptible sleep holding the mutex forever
   because no more events will arrive.

CVSS

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

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 (1)

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

Linux — Linux KernelAI

Referencias

JSON original (NVD)

Mostrar
{
  "id": "CVE-2026-89732",
  "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": "ddf8abd2599491cbad959c700b90ba72a5dce8d0",
              "lessThan": "fbe3db4b650c284df8eb4cb68eebcf270cf861b5",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0",
              "lessThan": "30430509c156e1df2bdafd5f1cadb160e53db5d6",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0",
              "lessThan": "bafddd0f20b5228760be303aa69c58502e92309c",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0",
              "lessThan": "b0a6bfac0c3c3edf5b2ecaee87a09234601fe78d",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0",
              "lessThan": "fd20cc68bbdb5620696ac108e8f2efd180fe2c1a",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0",
              "lessThan": "34e88f53614640b59039a46717fb6142e9871022",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0",
              "lessThan": "eac233e63f9db82ba874e3cccafaafab162999e0",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "ddf8abd2599491cbad959c700b90ba72a5dce8d0",
              "lessThan": "569dd7e5dcffe1e1c6b26ca2cd3be57eb433e082",
              "versionType": "git"
            }
          ],
          "programFiles": [
            "drivers/usb/gadget/function/f_fs.c"
          ],
          "defaultStatus": "unaffected"
        },
        {
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "product": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "2.6.35"
            },
            {
              "status": "unaffected",
              "version": "0",
              "lessThan": "2.6.35",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "5.10.270",
              "versionType": "semver",
              "lessThanOrEqual": "5.10.*"
            },
            {
              "status": "unaffected",
              "version": "5.15.221",
              "versionType": "semver",
              "lessThanOrEqual": "5.15.*"
            },
            {
              "status": "unaffected",
              "version": "6.1.188",
              "versionType": "semver",
              "lessThanOrEqual": "6.1.*"
            },
            {
              "status": "unaffected",
              "version": "6.6.157",
              "versionType": "semver",
              "lessThanOrEqual": "6.6.*"
            },
            {
              "status": "unaffected",
              "version": "6.12.109",
              "versionType": "semver",
              "lessThanOrEqual": "6.12.*"
            },
            {
              "status": "unaffected",
              "version": "6.18.50",
              "versionType": "semver",
              "lessThanOrEqual": "6.18.*"
            },
            {
              "status": "unaffected",
              "version": "7.2.4",
              "versionType": "semver",
              "lessThanOrEqual": "7.2.*"
            },
            {
              "status": "unaffected",
              "version": "7.3-rc1",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ],
          "programFiles": [
            "drivers/usb/gadget/function/f_fs.c"
          ],
          "defaultStatus": "affected"
        }
      ]
    }
  ],
  "published": "2026-09-11T20:20:03.600",
  "references": [
    {
      "url": "https://git.kernel.org/stable/c/30430509c156e1df2bdafd5f1cadb160e53db5d6",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/34e88f53614640b59039a46717fb6142e9871022",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/569dd7e5dcffe1e1c6b26ca2cd3be57eb433e082",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/b0a6bfac0c3c3edf5b2ecaee87a09234601fe78d",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/bafddd0f20b5228760be303aa69c58502e92309c",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/eac233e63f9db82ba874e3cccafaafab162999e0",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/fbe3db4b650c284df8eb4cb68eebcf270cf861b5",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    },
    {
      "url": "https://git.kernel.org/stable/c/fd20cc68bbdb5620696ac108e8f2efd180fe2c1a",
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "vulnStatus": "Received",
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nusb: gadget: f_fs: Prevent deadlock during ep0 read loop\n\nCurrently, ffs_ep0_read() holds ffs->mutex when it prepares to go to\nsleep waiting for an event. When no setup events are pending, it calls\nwait_event_interruptible_exclusive_locked_irq() with the mutex still\nheld. The wait macro deliberately drops the waitqueue spinlock before\nsleeping but does not drop the mutex.\n\nIf a userspace daemon is polling ep0 via read() and the gadget is\nasynchronously torn down via configfs (e.g., echo \"\" > UDC), a\ndeadlock can occur:\n\n1. The configfs teardown calls functionfs_unbind(), which queues a\n   FUNCTIONFS_UNBIND event.\n2. The daemon wakes up, consumes the event, and drops the mutex.\n3. However, if the daemon loops and immediately issues another read()\n   before exiting, it reacquires ffs->mutex and again goes into an\n   interruptible sleep.\n4. Meanwhile, functionfs_unbind() continues execution and attempts to\n   acquire ffs->mutex to tear down ep0req.\n5. The kernel deadlocks because the configfs thread is stuck in an\n   uninterruptible sleep waiting for the mutex, while the userspace\n   daemon is in an interruptible sleep holding the mutex forever\n   because no more events will arrive.\n\nTo fix this, we drop both the waitqueue spinlock and ffs->mutex before\ngoing to sleep, and use wait_event_interruptible_exclusive() instead.\nUpon waking up, we jump back to the `retry` label to safely reacquire\nthe mutex and re-evaluate the state machine. By not sleeping with\nffs->mutex held, we natively decouple gadget teardowns (which require\nthe mutex) from userspace polling."
    }
  ],
  "lastModified": "2026-09-14T13:19:22.293",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}