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

s390/mm: Do not map lowcore with identity mapping

Since the identity mapping is pinned to address zero the lowcore is always
also mapped to address zero, this happens regardless of the relocate_lowcore
command line option. If the option is specified the lowcore is mapped
twice, instead of only once.

This means that NULL pointer accesses will succeed instead of causing an
exception (low address protection still applies, but covers only parts).
To fix this never map the first two pages of physical memory with the
identity mapping.
History

Fri, 05 Sep 2025 17:30:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: s390/mm: Do not map lowcore with identity mapping Since the identity mapping is pinned to address zero the lowcore is always also mapped to address zero, this happens regardless of the relocate_lowcore command line option. If the option is specified the lowcore is mapped twice, instead of only once. This means that NULL pointer accesses will succeed instead of causing an exception (low address protection still applies, but covers only parts). To fix this never map the first two pages of physical memory with the identity mapping.
Title s390/mm: Do not map lowcore with identity mapping
References

cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2025-09-05T17:20:33.075Z

Reserved: 2025-04-16T04:51:24.033Z

Link: CVE-2025-38733

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2025-09-05T18:15:42.550

Modified: 2025-09-05T18:15:42.550

Link: CVE-2025-38733

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.