gsd-2021-46935
Vulnerability from gsd
Modified
2024-02-26 06:03
Details
In the Linux kernel, the following vulnerability has been resolved: binder: fix async_free_space accounting for empty parcels In 4.13, commit 74310e06be4d ("android: binder: Move buffer out of area shared with user space") fixed a kernel structure visibility issue. As part of that patch, sizeof(void *) was used as the buffer size for 0-length data payloads so the driver could detect abusive clients sending 0-length asynchronous transactions to a server by enforcing limits on async_free_size. Unfortunately, on the "free" side, the accounting of async_free_space did not add the sizeof(void *) back. The result was that up to 8-bytes of async_free_space were leaked on every async transaction of 8-bytes or less. These small transactions are uncommon, so this accounting issue has gone undetected for several years. The fix is to use "buffer_size" (the allocated buffer size) instead of "size" (the logical buffer size) when updating the async_free_space during the free operation. These are the same except for this corner case of asynchronous transactions with payloads < 8 bytes.
Aliases


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{
  "gsd": {
    "metadata": {
      "exploitCode": "unknown",
      "remediation": "unknown",
      "reportConfidence": "confirmed",
      "type": "vulnerability"
    },
    "osvSchema": {
      "aliases": [
        "CVE-2021-46935"
      ],
      "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbinder: fix async_free_space accounting for empty parcels\n\nIn 4.13, commit 74310e06be4d (\"android: binder: Move buffer out of area shared with user space\")\nfixed a kernel structure visibility issue. As part of that patch,\nsizeof(void *) was used as the buffer size for 0-length data payloads so\nthe driver could detect abusive clients sending 0-length asynchronous\ntransactions to a server by enforcing limits on async_free_size.\n\nUnfortunately, on the \"free\" side, the accounting of async_free_space\ndid not add the sizeof(void *) back. The result was that up to 8-bytes of\nasync_free_space were leaked on every async transaction of 8-bytes or\nless.  These small transactions are uncommon, so this accounting issue\nhas gone undetected for several years.\n\nThe fix is to use \"buffer_size\" (the allocated buffer size) instead of\n\"size\" (the logical buffer size) when updating the async_free_space\nduring the free operation. These are the same except for this\ncorner case of asynchronous transactions with payloads \u003c 8 bytes.",
      "id": "GSD-2021-46935",
      "modified": "2024-02-26T06:03:52.280296Z",
      "schema_version": "1.4.0"
    }
  },
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbinder: fix async_free_space accounting for empty parcels\n\nIn 4.13, commit 74310e06be4d (\"android: binder: Move buffer out of area shared with user space\")\nfixed a kernel structure visibility issue. As part of that patch,\nsizeof(void *) was used as the buffer size for 0-length data payloads so\nthe driver could detect abusive clients sending 0-length asynchronous\ntransactions to a server by enforcing limits on async_free_size.\n\nUnfortunately, on the \"free\" side, the accounting of async_free_space\ndid not add the sizeof(void *) back. The result was that up to 8-bytes of\nasync_free_space were leaked on every async transaction of 8-bytes or\nless.  These small transactions are uncommon, so this accounting issue\nhas gone undetected for several years.\n\nThe fix is to use \"buffer_size\" (the allocated buffer size) instead of\n\"size\" (the logical buffer size) when updating the async_free_space\nduring the free operation. These are the same except for this\ncorner case of asynchronous transactions with payloads \u003c 8 bytes."
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            "value": "En el kernel de Linux, se resolvi\u00f3 la siguiente vulnerabilidad: binder: corrige la contabilidad async_free_space para paquetes vac\u00edos En 4.13, el commit 74310e06be4d (\"android: binder: mover el b\u00fafer fuera del \u00e1rea compartida con el espacio del usuario\") solucion\u00f3 un problema de visibilidad de la estructura del kernel. Como parte de ese parche, se us\u00f3 sizeof(void *) como tama\u00f1o de b\u00fafer para cargas de datos de longitud 0, de modo que el controlador pudiera detectar clientes abusivos que enviaran transacciones asincr\u00f3nicas de longitud 0 a un servidor imponiendo l\u00edmites en async_free_size. Desafortunadamente, en el lado \"libre\", la contabilidad de async_free_space no volvi\u00f3 a agregar el tama\u00f1o de (void *). El resultado fue que se filtraron hasta 8 bytes de async_free_space en cada transacci\u00f3n as\u00edncrona de 8 bytes o menos. Estas peque\u00f1as transacciones son poco comunes, por lo que este problema contable ha pasado desapercibido durante varios a\u00f1os. La soluci\u00f3n es utilizar \"buffer_size\" (el tama\u00f1o del b\u00fafer asignado) en lugar de \"size\" (el tama\u00f1o del b\u00fafer l\u00f3gico) al actualizar async_free_space durante la operaci\u00f3n libre. Son iguales excepto por este caso de esquina de transacciones asincr\u00f3nicas con payloads \u0026lt;8 bytes."
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        "id": "CVE-2021-46935",
        "lastModified": "2024-04-10T18:24:38.927",
        "metrics": {
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                "attackComplexity": "LOW",
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}


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