KVM: arm64: Fix spurious warning for benign stage 2 teardown race

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Summary

CVECVE-2026-98468
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-18 16:16:57 UTC
Updated2026-10-19 10:18:56 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: KVM: arm64: Fix spurious warning for benign stage 2 teardown race kvmtool was used to establish an L1 guest with 8 CPUs and 8 GiB of RAM, an L2 guest with 4 CPUs and 4 GiB of RAM and an L3 guest with 2 CPUs and 2 GiB of RAM, all of which was then exited. Under memory pressure in the L0 host warnings were observed due to migration triggered by compaction: WARNING: arch/arm64/kvm/mmu.c:336 at __unmap_stage2_range+0x64/0x80, CPU#5: kcompactd0/66 Which was, in turn, triggered by an MMU notifier for the host invalidation: mmu_notifier_invalidate_range_start() -> ... -> kvm_mmu_notifier_invalidate_range_start() -> kvm_mmu_unmap_gfn_range() -> kvm_unmap_gfn_range() -> kvm_nested_s2_unmap() -> kvm_stage2_unmap_range() -> __unmap_stage2_range() -> stage2_apply_range() <- -EINVAL, triggering a WARN_ON() Racing with L0's teardown of stage 2 page tables: exit_mm() -> mmput() -> __mmput() -> exit_mmap() -> mmu_notifier_release() -> ... -> kvm_mmu_notifier_release() -> kvm_flush_shadow_all() -> kvm_arch_flush_shadow_all() -> kvm_free_stage2_pgd() -> [ acquire kvm->mmu_lock for write ] -> mmu->pgt = NULL [ among other tasks ] -> [ release kvm->mmu_lock for write ] It turns out there is a benign race resulting in a spurious warning: Thread A - notify: migration | Thread B - notify: release -------------------------------|--------------------------------- < kvm->mmu_lock held > | stage2_apply_range() | get mmu->pgt, check !NULL | ... | kvm_arch_flush_shadow_all() cond_resched_rwlock_write(); | < contend, sleep kvm->mmu_lock > < drop kvm->mmu_lock > | < acquire kvm->mmu_lock> | ... | kvm_free_stage2_pgd() | mmu->pgt = NULL | < invalidate MMU > | ... | < release kvm->mmu_lock > [ scheduled ] | stage2_apply_range() | < loop to next > | get, mmu->pgt, check !NULL | is NULL, return -EINVAL | __unmap_stage2_range() | WARN_ON(-EINVAL) <--- entirely spurious - the race was handled correctly. Fix the spurious warning by updating stage2_apply_range() to no longer treat concurrent PGT teardown on lock release as an error - whether the walker is tearing down page tables or doing something else this is a legitimate reason to abort the operation without error. This keeps the warning in place for all other circumstances. In practice only __unmap_stage2_range() actually does anything with the error so this only impacts that.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected ec14c272408af43d392f65f55e66f3b94fc61921 f44a92633136b409ebb9b7036fceb7e11de60a20 git Not specified
CNA Linux Linux affected ec14c272408af43d392f65f55e66f3b94fc61921 c23ed110d27ba99cf3a881986514f79aacedf476 git Not specified
CNA Linux Linux affected ec14c272408af43d392f65f55e66f3b94fc61921 330346dda3bf5f8a3b06723024f7d906326270cf git Not specified
CNA Linux Linux affected ec14c272408af43d392f65f55e66f3b94fc61921 38b70fc453c3112f1a62583b89903ae41116cc27 git Not specified
CNA Linux Linux affected 6.11 Not specified
CNA Linux Linux unaffected 6.11 semver Not specified
CNA Linux Linux unaffected 6.12.112 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.55 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.9 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/c23ed110d27ba99cf3a881986514f79aacedf476 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/330346dda3bf5f8a3b06723024f7d906326270cf 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/38b70fc453c3112f1a62583b89903ae41116cc27 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/f44a92633136b409ebb9b7036fceb7e11de60a20 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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