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CVE-2025-39790

Full vulnerability record from the local CVENow database.

Description

In the Linux kernel, the following vulnerability has been resolved: bus: mhi: host: Detect events pointing to unexpected TREs When a remote device sends a completion event to the host, it contains a pointer to the consumed TRE. The host uses this pointer to process all of the TREs between it and the host's local copy of the ring's read pointer. This works when processing completion for chained transactions, but can lead to nasty results if the device sends an event for a single-element transaction with a read pointer that is multiple elements ahead of the host's read pointer. For instance, if the host accesses an event ring while the device is updating it, the pointer inside of the event might still point to an old TRE. If the host uses the channel's xfer_cb() to directly free the buffer pointed to by the TRE, the buffer will be double-freed. This behavior was observed on an ep that used upstream EP stack without 'commit 6f18d174b73d ("bus: mhi: ep: Update read pointer only after buffer is written")'. Where the device updated the events ring pointer before updating the event contents, so it left a window where the host was able to access the stale data the event pointed to, before the device had the chance to update them. The usual pattern was that the host received an event pointing to a TRE that is not immediately after the last processed one, so it got treated as if it was a chained transaction, processing all of the TREs in between the two read pointers. This commit aims to harden the host by ensuring transactions where the event points to a TRE that isn't local_rp + 1 are chained. [mani: added stable tag and reworded commit message]

Severity
HIGH
CVSS score
7.8 (v3.1)
Vulnerability status
Modified
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2025-09-11 17:15:45.360000
Last modified
2026-10-19 21:10:00.160000
View original CVE JSON 
{
  "id": "CVE-2025-39790",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2025-09-11T17:15:45.360",
  "lastModified": "2026-10-19T21:10:00.160",
  "vulnStatus": "Modified",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbus: mhi: host: Detect events pointing to unexpected TREs\n\nWhen a remote device sends a completion event to the host, it contains a\npointer to the consumed TRE. The host uses this pointer to process all of\nthe TREs between it and the host's local copy of the ring's read pointer.\nThis works when processing completion for chained transactions, but can\nlead to nasty results if the device sends an event for a single-element\ntransaction with a read pointer that is multiple elements ahead of the\nhost's read pointer.\n\nFor instance, if the host accesses an event ring while the device is\nupdating it, the pointer inside of the event might still point to an old\nTRE. If the host uses the channel's xfer_cb() to directly free the buffer\npointed to by the TRE, the buffer will be double-freed.\n\nThis behavior was observed on an ep that used upstream EP stack without\n'commit 6f18d174b73d (\"bus: mhi: ep: Update read pointer only after buffer\nis written\")'. Where the device updated the events ring pointer before\nupdating the event contents, so it left a window where the host was able to\naccess the stale data the event pointed to, before the device had the\nchance to update them. The usual pattern was that the host received an\nevent pointing to a TRE that is not immediately after the last processed\none, so it got treated as if it was a chained transaction, processing all\nof the TREs in between the two read pointers.\n\nThis commit aims to harden the host by ensuring transactions where the\nevent points to a TRE that isn't local_rp + 1 are chained.\n\n[mani: added stable tag and reworded commit message]"
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nbus: mhi: host: Detectar eventos que apuntan a TREs inesperados\n\nCuando un dispositivo remoto envía un evento de completado al host, este contiene un puntero al TRE consumido. El host usa este puntero para procesar todos los TREs entre este y la copia local del host del puntero de lectura del anillo. Esto funciona al procesar la completación para transacciones encadenadas, pero puede llevar a resultados desagradables si el dispositivo envía un evento para una transacción de un solo elemento con un puntero de lectura que está múltiples elementos por delante del puntero de lectura del host.\n\nPor ejemplo, si el host accede a un anillo de eventos mientras el dispositivo lo está actualizando, el puntero dentro del evento podría seguir apuntando a un TRE antiguo. Si el host usa el xfer_cb() del canal para liberar directamente el búfer apuntado por el TRE, el búfer será liberado dos veces.\n\nEste comportamiento fue observado en un ep que usaba la pila EP ascendente sin el 'commit 6f18d174b73d (“bus: mhi: ep: Actualizar puntero de lectura solo después de que el búfer sea escrito”)'. Donde el dispositivo actualizó el puntero del anillo de eventos antes de actualizar el contenido del evento, por lo que dejó una ventana donde el host pudo acceder a los datos obsoletos a los que apuntaba el evento, antes de que el dispositivo tuviera la oportunidad de actualizarlos. El patrón usual era que el host recibía un evento apuntando a un TRE que no está inmediatamente después del último procesado, por lo que fue tratado como si fuera una transacción encadenada, procesando todos los TREs entre los dos punteros de lectura.\n\nEste commit tiene como objetivo fortalecer el host asegurando que las transacciones donde el evento apunta a un TRE que no es local_rp + 1 estén encadenadas.\n\n[mani: se añadió la etiqueta stable y se reescribió el mensaje del commit]"
    }
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          "product": "SIMATIC CN 4100",
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