CVE-2025-38689 (GCVE-0-2025-38689)
Vulnerability from cvelistv5
Published
2025-09-04 15:32
Modified
2025-09-04 15:32
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
x86/fpu: Fix NULL dereference in avx512_status()
Problem
-------
With CONFIG_X86_DEBUG_FPU enabled, reading /proc/[kthread]/arch_status
causes a warning and a NULL pointer dereference.
This is because the AVX-512 timestamp code uses x86_task_fpu() but
doesn't check it for NULL. CONFIG_X86_DEBUG_FPU addles that function
for kernel threads (PF_KTHREAD specifically), making it return NULL.
The point of the warning was to ensure that kernel threads only access
task->fpu after going through kernel_fpu_begin()/_end(). Note: all
kernel tasks exposed in /proc have a valid task->fpu.
Solution
--------
One option is to silence the warning and check for NULL from
x86_task_fpu(). However, that warning is fairly fresh and seems like a
defense against misuse of the FPU state in kernel threads.
Instead, stop outputting AVX-512_elapsed_ms for kernel threads
altogether. The data was garbage anyway because avx512_timestamp is
only updated for user threads, not kernel threads.
If anyone ever wants to track kernel thread AVX-512 use, they can come
back later and do it properly, separate from this bug fix.
[ dhansen: mostly rewrite changelog ]
References
Impacted products
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{
"url": "https://git.kernel.org/stable/c/31cd31c9e17ece125aad27259501a2af69ccb020"
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"title": "x86/fpu: Fix NULL dereference in avx512_status()",
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"cveId": "CVE-2025-38689",
"datePublished": "2025-09-04T15:32:43.530Z",
"dateReserved": "2025-04-16T04:51:24.032Z",
"dateUpdated": "2025-09-04T15:32:43.530Z",
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}
}
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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.
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