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CVE-2025-37878

Estado: ModificadaMedia (5.5)—

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

perf/core: Fix WARN_ON(!ctx) in __free_event() for partial init

Move the get_ctx(child_ctx) call and the child_event->ctx assignment to occur immediately after the child event is allocated. Ensure that child_event->ctx is non-NULL before any subsequent error path within inherit_event calls free_event(), satisfying the assumptions of the cleanup code.

Details:

There's no clear Fixes tag, because this bug is a side-effect of multiple interacting commits over time (up to 15 years old), not a single regression.

The code initially incremented refcount then assigned context immediately after the child_event was created. Later, an early validity check for child_event was added before the refcount/assignment.

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Even later, a WARN_ON_ONCE() cleanup check was added, assuming event->ctx is valid if the pmu_ctx is valid. The problem is that the WARN_ON_ONCE() could trigger after the initial check passed but before child_event->ctx was assigned, violating its precondition. The solution is to assign child_event->ctx right after its initial validation. This ensures the context exists for any subsequent checks or cleanup routines, resolving the WARN_ON_ONCE().

To resolve it, defer the refcount update and child_event->ctx assignment directly after child_event->pmu_ctx is set but before checking if the parent event is orphaned. The cleanup routine depends on event->pmu_ctx being non-NULL before it verifies event->ctx is non-NULL. This also maintains the author's original intent of passing in child_ctx to find_get_pmu_context before its refcount/assignment.

[ mingo: Expanded the changelog from another email by Gabriel Shahrouzi. ]

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 (1)

Linux — Linux Kernel

CWE

Referencias

JSON original (NVD)

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  "id": "CVE-2025-37878",
  "cveTags": [],
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        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
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          "version": "3.1",
          "baseScore": 5.5,
          "attackVector": "LOCAL",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "NONE"
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        "exploitabilityScore": 1.8
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  "published": "2025-05-09T07:16:09.020",
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      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nperf/core: Fix WARN_ON(!ctx) in __free_event() for partial init\n\nMove the get_ctx(child_ctx) call and the child_event->ctx assignment to\noccur immediately after the child event is allocated. Ensure that\nchild_event->ctx is non-NULL before any subsequent error path within\ninherit_event calls free_event(), satisfying the assumptions of the\ncleanup code.\n\nDetails:\n\nThere's no clear Fixes tag, because this bug is a side-effect of\nmultiple interacting commits over time (up to 15 years old), not\na single regression.\n\nThe code initially incremented refcount then assigned context\nimmediately after the child_event was created. Later, an early\nvalidity check for child_event was added before the\nrefcount/assignment. Even later, a WARN_ON_ONCE() cleanup check was\nadded, assuming event->ctx is valid if the pmu_ctx is valid.\nThe problem is that the WARN_ON_ONCE() could trigger after the initial\ncheck passed but before child_event->ctx was assigned, violating its\nprecondition. The solution is to assign child_event->ctx right after\nits initial validation. This ensures the context exists for any\nsubsequent checks or cleanup routines, resolving the WARN_ON_ONCE().\n\nTo resolve it, defer the refcount update and child_event->ctx assignment\ndirectly after child_event->pmu_ctx is set but before checking if the\nparent event is orphaned. The cleanup routine depends on\nevent->pmu_ctx being non-NULL before it verifies event->ctx is\nnon-NULL. This also maintains the author's original intent of passing\nin child_ctx to find_get_pmu_context before its refcount/assignment.\n\n[ mingo: Expanded the changelog from another email by Gabriel Shahrouzi. ]"
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: perf/core: Arregla WARN_ON(!ctx) en __free_event() para init parcial Mueve la llamada get_ctx(child_ctx) y la asignación child_event->ctx para que ocurran inmediatamente después de que se asigne el evento secundario. Asegúrate de que child_event->ctx no sea NULL antes de cualquier ruta de error posterior dentro de las llamadas heritage_event a free_event(), satisfaciendo las suposiciones del código de limpieza. Detalles: No hay una etiqueta Fixes clara, porque este error es un efecto secundario de múltiples confirmaciones interactivas a lo largo del tiempo (hasta 15 años de antigüedad), no una sola regresión. El código inicialmente incrementó refcount y luego asignó contexto inmediatamente después de que se creara child_event. Más tarde, se agregó una comprobación de validez temprana para child_event antes de refcount/assignment. Incluso más tarde, se agregó una comprobación de limpieza WARN_ON_ONCE(), asumiendo que event->ctx es válido si pmu_ctx es válido. El problema radica en que WARN_ON_ONCE() podría activarse después de que se supere la comprobación inicial, pero antes de que se asignara child_event->ctx, incumpliendo su precondición. La solución es asignar child_event->ctx justo después de su validación inicial. Esto garantiza la existencia del contexto para cualquier comprobación o rutina de limpieza posterior, resolviendo WARN_ON_ONCE(). Para solucionarlo, posponga la actualización del recuento de referencias y la asignación de child_event->ctx justo después de que se configure child_event->pmu_ctx, pero antes de comprobar si el evento principal está huérfano. La rutina de limpieza depende de que event->pmu_ctx no sea NULL antes de verificar que event->ctx no sea NULL. Esto también mantiene la intención original del autor de pasar child_ctx a find_get_pmu_context antes de su recuento de referencias/asignación. [mingo: Registro de cambios ampliado de otro correo electrónico de Gabriel Shahrouzi]."
    }
  ],
  "lastModified": "2026-06-17T09:15:37.220",
  "configurations": [
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