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
Configurations
Configuration 1 (hide)
|
History
24 Nov 2025, 19:47
| Type | Values Removed | Values Added |
|---|---|---|
| First Time |
Linux
Linux linux Kernel |
|
| CWE | CWE-476 | |
| CVSS |
v2 : v3 : |
v2 : unknown
v3 : 5.5 |
| CPE | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.17:rc1:*:*:*:*:*:* |
|
| References | () https://git.kernel.org/stable/c/2ca887e81095b99d890a8878841f36f4920181e6 - Patch | |
| References | () https://git.kernel.org/stable/c/31cd31c9e17ece125aad27259501a2af69ccb020 - Patch |
04 Sep 2025, 16:15
| Type | Values Removed | Values Added |
|---|---|---|
| New CVE |
Information
Published : 2025-09-04 16:15
Updated : 2025-11-24 19:47
NVD link : CVE-2025-38689
Mitre link : CVE-2025-38689
CVE.ORG link : CVE-2025-38689
JSON object : View
Products Affected
linux
- linux_kernel
CWE
CWE-476
NULL Pointer Dereference