x86/mce: use is_copy_from_user() to determine copy-from-user… (CVE-2025-39989)

Summary

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

Original description

The description as published by the source.

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 code
specified in _ASM_EXTABLE_FAULT() and return a -EFAULT to user space.

For instr case:

If a poison found while instruction fetching in user space, full recovery
is possible. User process takes #PF, Linux allocates a new page and fills
by reading from storage.

3. What actually happens and why

For copyin case: kernel panic since v5.17

Commit 4c132d1d844a ("x86/futex: Remove .fixup usage") introduced a new
extable fixup type, EX_TYPE_EFAULT_REG, and later patches updated the
extable…

Source: OSV.dev (Open Source Vulnerabilities) NVD OSV

Affected packages

Linux Kernel

[{"type":"ECOSYSTEM","events":[{"introduced":"5.17.0"},{"fixed":"6.6.89"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.23"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.13.11"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.14.0"},{"fixed":"6.14.2"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

BellSoft Alpaquita BELL-CVE-2025-39989 linux-lts
Debian DEBIAN-CVE-2025-39989 linux
Ubuntu UBUNTU-CVE-2025-39989 linux-hwe-edge