CVE-2025-68179: s390: Disable ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP
In the Linux kernel, the following vulnerability has been resolved:
s390: Disable ARCHWANTOPTIMIZEHUGETLBVMEMMAP
As reported by Luiz Capitulino enabling HVO on s390 leads to reproducible crashes. The problem is that kernel page tables are modified without flushing corresponding TLB entries.
Even if it looks like the empty flushtlball() implementation on s390 is the problem, it is actually a different problem: on s390 it is not allowed to replace an active/valid page table entry with another valid page table entry without the detour over an invalid entry. A direct replacement may lead to random crashes and/or data corruption.
In order to invalidate an entry special instructions have to be used (e.g. ipte or idte). Alternatively there are also special instructions available which allow to replace a valid entry with a different valid entry (e.g. crdte or cspg).
Given that the HVO code currently does not provide the hooks to allow for an implementation which is compliant with the s390 architecture requirements, disable ARCHWANTOPTIMIZEHUGETLBVMEMMAP again, which is basically a revert of the original patch which enabled it.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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ubuntu/linux-aws-6.8to a version that resolves this vulnerability.Fixed in 6.8.0-1050.53~22.04.1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 6.17.0-14.14 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 6.17.0-1007.7 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 6.17.0-1008.8 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 6.17.0-1007.7 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 6.17.0-1007.7 - Upgrade
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ubuntu/linux-raspito a version that resolves this vulnerability.Fixed in 6.17.0-1008.8 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 6.17.0-1006.7 - Upgrade
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 6.17.0-14.14.1 - Configuration
Disable ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP on s390; this reverts the patch that enabled it.
Linux kernel on s390 ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP = disabled
Event History
Frequently Asked Questions
What is the severity of CVE-2025-68179?
CVE-2025-68179 has a moderate severity due to potential crashes related to kernel page table modifications.
What does CVE-2025-68179 affect?
CVE-2025-68179 affects the Linux kernel, specifically the s390 architecture.
How do I fix CVE-2025-68179?
To address CVE-2025-68179, users should disable ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP in their kernel configuration.
When was CVE-2025-68179 disclosed?
CVE-2025-68179 was disclosed following reports of reproducible crashes associated with enabling HVO on s390.
What are the consequences of not addressing CVE-2025-68179?
Failure to address CVE-2025-68179 may result in system crashes and instability within the affected Linux kernel versions.