Executive brief
A vulnerability in the Linux kernel for s390 architecture systems could allow a local user to cause a system hang or denial of service. The issue occurs when the system attempts to access certain memory locations used for secure execution, leading to an infinite loop that prevents the system from continuing normal operations. This affects IBM Z and other s390-based infrastructure running specific versions of the Linux kernel.
Technical details
A vulnerability exists in the s390 architecture implementation of the Linux kernel due to the way load_unaligned_zeropad() interacts with secure storage. When reading eight bytes from unaligned addresses that cross page boundaries into memory donated to the Ultravisor for secure execution, the do_secure_storage_access() exception handler fails to correctly process the resulting exception. This leads to an infinite exception loop that cannot be resolved, resulting in a local denial of service. The fix involves reverting DCACHE_WORD_ACCESS support on s390 as a temporary workaround until a proper fix for secure storage access exceptions is implemented.
Affected products
- Linux Linux 6.7 to 7.1.4
Timeline
- 2026-06-11: patched: Initial fix/revert authored by Heiko Carstens
- 2026-07-25: disclosed: CVE published to NVD