From 2986a625740599fe6e7635b0586fed2a95bcd1f7 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Thu, 4 Jun 2026 17:11:56 +0200 Subject: [PATCH] KVM: arm64: Omit tag sync on stage-2 mappings of the zero page Commit f620d66af316 ("arm64: mte: Do not flag the zero page as PG_mte_tagged") removed the PG_mte_tagged flag from the zero page, but missed a KVM code path that may set this flag on the zero page when it is used in a stage-2 CoW mapping of anonymous memory. So disregard the zero page explicitly in sanitise_mte_tags(). Fixes: f620d66af316 ("arm64: mte: Do not flag the zero page as PG_mte_tagged") Cc: stable@vger.kernel.org # 5.10.x Suggested-by: Catalin Marinas Signed-off-by: Ard Biesheuvel Reviewed-by: Catalin Marinas Signed-off-by: Will Deacon --- arch/arm64/kvm/mmu.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index d089c107d9b7..445d6cf035c9 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -1479,6 +1479,11 @@ static void sanitise_mte_tags(struct kvm *kvm, kvm_pfn_t pfn, if (!kvm_has_mte(kvm)) return; + if (is_zero_pfn(pfn)) { + WARN_ON_ONCE(nr_pages != 1); + return; + } + if (folio_test_hugetlb(folio)) { /* Hugetlb has MTE flags set on head page only */ if (folio_try_hugetlb_mte_tagging(folio)) {