CVE-2026-89908

CVE-2026-89908 · LoongArch: KVM: Preserve memslot arch flags on KVM_MR_FLAGS_ONLY

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This page shows selected source facts. See the linked advisories for the complete description and affected versions.

In the Linux kernel, the following vulnerability has been resolved: LoongArch: KVM: Preserve memslot arch flags on KVM_MR_FLAGS_ONLY kvm_arch_prepare_memory_region() computes new->arch.flags, i.e. whether a memslot is KVM_MEM_HUGEPAGE_CAPABLE or KVM_MEM_HUGEPAGE_INCAPABLE, only for KVM_MR_CREATE and KVM_MR_MOVE, and returns early for every other change. But the generic code allocates a zeroed memslot for every change and never copies old->arch, so after a KVM_MR_FLAGS_ONLY update, e.g. toggling KVM_MEM_LOG_DIRTY_PAGES for live migration, the active memslot has arch.flags == 0. With both flags clear, fault_supports_huge_mapping() falls through to the alignment check on the HVA range alone, which no longer verifies that the GPA and HVA have the same offset within a PMD. A memslot that was marked KVM_MEM_HUGEPAGE_INCAPABLE because of a GPA/HVA offset mismatch can then be mapped with PMD entries on read faults, and since kvm_map_page() aligns the gfn and the pfn independently, the guest ends up accessing the wrong host pages, exactly the "d -> f, e -> g" case described in the comment above the check. Carry the arch flags over from the old memslot for KVM_MR_FLAGS_ONLY, as the GPA, HVA and size are guaranteed to be unchanged for that case.

CVSS 8.8 · High · EPSS 0.2% · Fix available

Published

2026-09-16T10:32:06.599Z

Updated

2026-10-19T08:54:40.893Z

Stack: system

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