ghsa-6v6p-g835-47x6
Vulnerability from github
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.
{
"affected": [],
"aliases": [
"CVE-2025-38670"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-08-22T16:15:42Z",
"severity": null
},
"details": "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.",
"id": "GHSA-6v6p-g835-47x6",
"modified": "2025-08-28T15:30:39Z",
"published": "2025-08-22T18:31:23Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-38670"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/0f67015d72627bad72da3c2084352e0aa134416b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/407047893a64399f2d2390ff35cc6061107d805d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/708fd522b86d2a9544c34ec6a86fa3fc23336525"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9433a5f437b0948d6a2d8a02ad7a42ab7ca27a61"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a6b0cb523eaa01efe8a3f76ced493ba60674c6e6"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d42e6c20de6192f8e4ab4cf10be8c694ef27e8cb"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.