Bug 2461528 (CVE-2026-31568)

Summary: CVE-2026-31568 kernel: s390/mm: Add missing secure storage access fixups for donated memory
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel. This vulnerability, located in the s390/mm component, is due to missing secure storage access fixups for memory donated to the Ultravisor. When secure storage access exceptions occur for such memory, the kernel can enter an unresolvable loop. This can lead to a system hang or crash, resulting in a Denial of Service (DoS).
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-04-24 15:06:43 UTC 
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.
Comment 1 Keith Grant 2026-04-24 17:56:22 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026042401-CVE-2026-31568-cefd@gregkh/T