SB20260912333 - Expected behavior violation in Linux kernel include asm

Description

This security bulletin contains information about 1 vulnerability.

1) Expected behavior violation (CVE-ID: CVE-2026-89459)

CWE-ID: CWE-440 - Expected Behavior Violation

CVSSv4: 2 [CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]

The vulnerability allows a local user to prevent the exception return path from repairing the per-CPU address register after migration.

The vulnerability exists due to incorrect assembler macro argument construction in MVIY_PERCPU() when building s390 kernel code with GNU as versions prior to binutils 2.39. A local user can trigger an interrupted per-CPU sequence that migrates between CPUs to prevent the exception return path from repairing the per-CPU address register after migration.

The omitted mviy instruction leaves the interrupted per-CPU sequence unmarked in lowcore.

Remediation

Install update from vendor's website.

References

• https://git.kernel.org/stable/c/101782f8945a125044347312d74d488c05741c4a
• https://git.kernel.org/stable/c/91770b08a120967077ae78600612f18bc5ee3caf