The kvm_age_hva callback may be called all the way concurrently while kvm_mmu_notifier_release() is running. The release function sets kvm->arch.pgd = NULL which the aging function however implicitly relies on in stage2_get_pud(). That means they can race and the aging function may dereference a NULL pgd pointer. This patch adds a check for that case, so that we leave the aging function silently. Cc: stable@xxxxxxxxxxxxxxx Fixes: 293f29363 ("kvm-arm: Unmap shadow pagetables properly") Signed-off-by: Alexander Graf <agraf@xxxxxxx> --- v1 -> v2: - Fix commit message - Add Fixes and stable tags --- virt/kvm/arm/mmu.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c index f2d5b6c..227931f 100644 --- a/virt/kvm/arm/mmu.c +++ b/virt/kvm/arm/mmu.c @@ -861,6 +861,10 @@ static pud_t *stage2_get_pud(struct kvm *kvm, struct kvm_mmu_memory_cache *cache pgd_t *pgd; pud_t *pud; + /* Do we clash with kvm_free_stage2_pgd()? */ + if (!kvm->arch.pgd) + return NULL; + pgd = kvm->arch.pgd + stage2_pgd_index(addr); if (WARN_ON(stage2_pgd_none(*pgd))) { if (!cache) -- 1.8.5.6