CVE-2026-31568

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

s390/mm: Add missing secure storage access fixups for donated memory

There are special cases where secure storage access exceptions happen

in a kernel context for pages that don't have the PG_arch_1 bit

set. That bit is set for non-exported guest secure storage (memory)

but is absent on storage donated to the Ultravisor since the kernel

isn't allowed to export donated pages.

Prior to this patch we would try to export the page by calling

arch_make_folio_accessible() which would instantly return since the

arch bit is absent signifying that the page was already exported and

no further action is necessary. This leads to secure storage access

exception loops which can never be resolved.

With this patch we unconditionally try to export and if that fails we

fixup.