CVE-2025-38670 (GCVE-0-2025-38670)
Vulnerability from cvelistv5
Published
2025-08-22 16:03
Modified
2025-08-28 14:44
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: arm64/entry: Mask DAIF in cpu_switch_to(), call_on_irq_stack() `cpu_switch_to()` and `call_on_irq_stack()` manipulate SP to change to different stacks along with the Shadow Call Stack if it is enabled. Those two stack changes cannot be done atomically and both functions can be interrupted by SErrors or Debug Exceptions which, though unlikely, is very much broken : if interrupted, we can end up with mismatched stacks and Shadow Call Stack leading to clobbered stacks. In `cpu_switch_to()`, it can happen when SP_EL0 points to the new task, but x18 stills points to the old task's SCS. When the interrupt handler tries to save the task's SCS pointer, it will save the old task SCS pointer (x18) into the new task struct (pointed to by SP_EL0), clobbering it. In `call_on_irq_stack()`, it can happen when switching from the task stack to the IRQ stack and when switching back. In both cases, we can be interrupted when the SCS pointer points to the IRQ SCS, but SP points to the task stack. The nested interrupt handler pushes its return addresses on the IRQ SCS. It then detects that SP points to the task stack, calls `call_on_irq_stack()` and clobbers the task SCS pointer with the IRQ SCS pointer, which it will also use ! This leads to tasks returning to addresses on the wrong SCS, or even on the IRQ SCS, triggering kernel panics via CONFIG_VMAP_STACK or FPAC if enabled. This is possible on a default config, but unlikely. However, when enabling CONFIG_ARM64_PSEUDO_NMI, DAIF is unmasked and instead the GIC is responsible for filtering what interrupts the CPU should receive based on priority. Given the goal of emulating NMIs, pseudo-NMIs can be received by the CPU even in `cpu_switch_to()` and `call_on_irq_stack()`, possibly *very* frequently depending on the system configuration and workload, leading to unpredictable kernel panics. Completely mask DAIF in `cpu_switch_to()` and restore it when returning. Do the same in `call_on_irq_stack()`, but restore and mask around the branch. Mask DAIF even if CONFIG_SHADOW_CALL_STACK is not enabled for consistency of behaviour between all configurations. Introduce and use an assembly macro for saving and masking DAIF, as the existing one saves but only masks IF.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/0f67015d72627bad72da3c2084352e0aa134416b
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/407047893a64399f2d2390ff35cc6061107d805d
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/708fd522b86d2a9544c34ec6a86fa3fc23336525
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/9433a5f437b0948d6a2d8a02ad7a42ab7ca27a61
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a6b0cb523eaa01efe8a3f76ced493ba60674c6e6
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d42e6c20de6192f8e4ab4cf10be8c694ef27e8cb
Impacted products
Vendor Product Version
Linux Linux Version: 402d2b1d54b7085d0c3bfd01fd50c2701dde64b3
Version: 4403c7b7e5e1ad09a266b6e399fd7bf97931508e
Version: 59b37fe52f49955791a460752c37145f1afdcad1
Version: 59b37fe52f49955791a460752c37145f1afdcad1
Version: 59b37fe52f49955791a460752c37145f1afdcad1
Version: 59b37fe52f49955791a460752c37145f1afdcad1
Version: e47ce4f11e26fa3ea99b09521da8b3ac3a7b578d
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   Linux Linux Version: 6.3
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{
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\narm64/entry: Mask DAIF in cpu_switch_to(), call_on_irq_stack()\n\n`cpu_switch_to()` and `call_on_irq_stack()` manipulate SP to change\nto different stacks along with the Shadow Call Stack if it is enabled.\nThose two stack changes cannot be done atomically and both functions\ncan be interrupted by SErrors or Debug Exceptions which, though unlikely,\nis very much broken : if interrupted, we can end up with mismatched stacks\nand Shadow Call Stack leading to clobbered stacks.\n\nIn `cpu_switch_to()`, it can happen when SP_EL0 points to the new task,\nbut x18 stills points to the old task\u0027s SCS. When the interrupt handler\ntries to save the task\u0027s SCS pointer, it will save the old task\nSCS pointer (x18) into the new task struct (pointed to by SP_EL0),\nclobbering it.\n\nIn `call_on_irq_stack()`, it can happen when switching from the task stack\nto the IRQ stack and when switching back. In both cases, we can be\ninterrupted when the SCS pointer points to the IRQ SCS, but SP points to\nthe task stack. The nested interrupt handler pushes its return addresses\non the IRQ SCS. It then detects that SP points to the task stack,\ncalls `call_on_irq_stack()` and clobbers the task SCS pointer with\nthe IRQ SCS pointer, which it will also use !\n\nThis leads to tasks returning to addresses on the wrong SCS,\nor even on the IRQ SCS, triggering kernel panics via CONFIG_VMAP_STACK\nor FPAC if enabled.\n\nThis is possible on a default config, but unlikely.\nHowever, when enabling CONFIG_ARM64_PSEUDO_NMI, DAIF is unmasked and\ninstead the GIC is responsible for filtering what interrupts the CPU\nshould receive based on priority.\nGiven the goal of emulating NMIs, pseudo-NMIs can be received by the CPU\neven in `cpu_switch_to()` and `call_on_irq_stack()`, possibly *very*\nfrequently depending on the system configuration and workload, leading\nto unpredictable kernel panics.\n\nCompletely mask DAIF in `cpu_switch_to()` and restore it when returning.\nDo the same in `call_on_irq_stack()`, but restore and mask around\nthe branch.\nMask DAIF even if CONFIG_SHADOW_CALL_STACK is not enabled for consistency\nof behaviour between all configurations.\n\nIntroduce and use an assembly macro for saving and masking DAIF,\nas the existing one saves but only masks IF."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2025-08-28T14:44:36.147Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/407047893a64399f2d2390ff35cc6061107d805d"
        },
        {
          "url": "https://git.kernel.org/stable/c/a6b0cb523eaa01efe8a3f76ced493ba60674c6e6"
        },
        {
          "url": "https://git.kernel.org/stable/c/9433a5f437b0948d6a2d8a02ad7a42ab7ca27a61"
        },
        {
          "url": "https://git.kernel.org/stable/c/708fd522b86d2a9544c34ec6a86fa3fc23336525"
        },
        {
          "url": "https://git.kernel.org/stable/c/0f67015d72627bad72da3c2084352e0aa134416b"
        },
        {
          "url": "https://git.kernel.org/stable/c/d42e6c20de6192f8e4ab4cf10be8c694ef27e8cb"
        }
      ],
      "title": "arm64/entry: Mask DAIF in cpu_switch_to(), call_on_irq_stack()",
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        "engine": "bippy-1.2.0"
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    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-38670",
    "datePublished": "2025-08-22T16:03:01.242Z",
    "dateReserved": "2025-04-16T04:51:24.031Z",
    "dateUpdated": "2025-08-28T14:44:36.147Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.1",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2025-38670\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-08-22T16:15:42.547\",\"lastModified\":\"2025-08-28T15:15:58.170\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\narm64/entry: Mask DAIF in cpu_switch_to(), call_on_irq_stack()\\n\\n`cpu_switch_to()` and `call_on_irq_stack()` manipulate SP to change\\nto different stacks along with the Shadow Call Stack if it is enabled.\\nThose two stack changes cannot be done atomically and both functions\\ncan be interrupted by SErrors or Debug Exceptions which, though unlikely,\\nis very much broken : if interrupted, we can end up with mismatched stacks\\nand Shadow Call Stack leading to clobbered stacks.\\n\\nIn `cpu_switch_to()`, it can happen when SP_EL0 points to the new task,\\nbut x18 stills points to the old task\u0027s SCS. When the interrupt handler\\ntries to save the task\u0027s SCS pointer, it will save the old task\\nSCS pointer (x18) into the new task struct (pointed to by SP_EL0),\\nclobbering it.\\n\\nIn `call_on_irq_stack()`, it can happen when switching from the task stack\\nto the IRQ stack and when switching back. In both cases, we can be\\ninterrupted when the SCS pointer points to the IRQ SCS, but SP points to\\nthe task stack. The nested interrupt handler pushes its return addresses\\non the IRQ SCS. It then detects that SP points to the task stack,\\ncalls `call_on_irq_stack()` and clobbers the task SCS pointer with\\nthe IRQ SCS pointer, which it will also use !\\n\\nThis leads to tasks returning to addresses on the wrong SCS,\\nor even on the IRQ SCS, triggering kernel panics via CONFIG_VMAP_STACK\\nor FPAC if enabled.\\n\\nThis is possible on a default config, but unlikely.\\nHowever, when enabling CONFIG_ARM64_PSEUDO_NMI, DAIF is unmasked and\\ninstead the GIC is responsible for filtering what interrupts the CPU\\nshould receive based on priority.\\nGiven the goal of emulating NMIs, pseudo-NMIs can be received by the CPU\\neven in `cpu_switch_to()` and `call_on_irq_stack()`, possibly *very*\\nfrequently depending on the system configuration and workload, leading\\nto unpredictable kernel panics.\\n\\nCompletely mask DAIF in `cpu_switch_to()` and restore it when returning.\\nDo the same in `call_on_irq_stack()`, but restore and mask around\\nthe branch.\\nMask DAIF even if CONFIG_SHADOW_CALL_STACK is not enabled for consistency\\nof behaviour between all configurations.\\n\\nIntroduce and use an assembly macro for saving and masking DAIF,\\nas the existing one saves but only masks IF.\"},{\"lang\":\"es\",\"value\":\"En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: arm64/entry: Mask DAIF en cpu_switch_to(), call_on_irq_stack() `cpu_switch_to()` y `call_on_irq_stack()` manipulan SP para cambiar a diferentes pilas junto con Shadow Call Stack si est\u00e1 habilitado. Estos dos cambios de pila no se pueden realizar de forma autom\u00e1tica y ambas funciones pueden ser interrumpidas por SErrors o Debug Exceptions, lo que, aunque poco probable, es muy problem\u00e1tico: si se interrumpe, podemos terminar con pilas desajustadas y Shadow Call Stack, lo que lleva a pilas da\u00f1adas. En `cpu_switch_to()`, puede ocurrir cuando SP_EL0 apunta a la nueva tarea, pero x18 todav\u00eda apunta al SCS de la tarea anterior. Cuando el manejador de interrupciones intenta guardar el puntero SCS de la tarea, guardar\u00e1 el antiguo puntero SCS de la tarea (x18) en la nueva estructura de la tarea (apuntada por SP_EL0), bloque\u00e1ndola. En `call_on_irq_stack()`, puede suceder al cambiar de la pila de tareas a la pila de IRQ y al volver a cambiar. En ambos casos, podemos ser interrumpidos cuando el puntero SCS apunta al SCS de IRQ, pero SP apunta a la pila de tareas. El manejador de interrupciones anidado empuja sus direcciones de retorno en el SCS de IRQ. Luego detecta que SP apunta a la pila de tareas, llama a `call_on_irq_stack()` y bloquea el puntero SCS de la tarea con el puntero SCS de IRQ, \u00a1que tambi\u00e9n usar\u00e1! Esto lleva a que las tareas regresen a direcciones en el SCS incorrecto, o incluso en el SCS de IRQ, lo que desencadena p\u00e1nicos del kernel a trav\u00e9s de CONFIG_VMAP_STACK o FPAC si est\u00e1 habilitado. Esto es posible en una configuraci\u00f3n predeterminada, pero poco probable. Sin embargo, al habilitar CONFIG_ARM64_PSEUDO_NMI, DAIF se desenmascara y, en su lugar, el GIC se encarga de filtrar las interrupciones que la CPU deber\u00eda recibir seg\u00fan su prioridad. Dado el objetivo de emular NMI, la CPU puede recibir pseudo-NMI incluso en `cpu_switch_to()` y `call_on_irq_stack()`, posiblemente con mucha frecuencia seg\u00fan la configuraci\u00f3n del sistema y la carga de trabajo, lo que provoca p\u00e1nicos de kernel impredecibles. Enmascare completamente DAIF en `cpu_switch_to()` y rest\u00e1urelo al regresar. Haga lo mismo en `call_on_irq_stack()`, pero rest\u00e1urelo y enmascare alrededor de la rama. Enmascare DAIF incluso si CONFIG_SHADOW_CALL_STACK no est\u00e1 habilitado para mantener la coherencia entre todas las configuraciones. Introduzca y utilice una macro de ensamblaje para guardar y enmascarar DAIF, ya que la existente guarda pero solo enmascara las interrupciones IF.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/0f67015d72627bad72da3c2084352e0aa134416b\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/407047893a64399f2d2390ff35cc6061107d805d\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/708fd522b86d2a9544c34ec6a86fa3fc23336525\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/9433a5f437b0948d6a2d8a02ad7a42ab7ca27a61\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/a6b0cb523eaa01efe8a3f76ced493ba60674c6e6\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/d42e6c20de6192f8e4ab4cf10be8c694ef27e8cb\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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