CVE-2025-39989

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

x86/mce: use is_copy_from_user() to determine copy-from-user context

Patch series "mm/hwpoison: Fix regressions in memory failure handling",

v4.

## 1. What am I trying to do:

This patchset resolves two critical regressions related to memory failure

handling that have appeared in the upstream kernel since version 5.17, as

compared to 5.10 LTS.

- copyin case: poison found in user page while kernel copying from user space

- instr case: poison found while instruction fetching in user space

## 2. What is the expected outcome and why

- For copyin case:

Kernel can recover from poison found where kernel is doing get_user() or

copy_from_user() if those places get an error return and the kernel return

-EFAULT to the process instead of crashing. More specifily, MCE handler

checks the fixup handler type to decide whether an in kernel #MC can be

recovered. When EX_TYPE_UACCESS is found, the PC jumps to recovery co

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References