On Thu, 2022-02-17 at 16:03 -0500, Paolo Bonzini wrote: > WARN and bail if KVM attempts to free a root that isn't backed by a shadow > page. KVM allocates a bare page for "special" roots, e.g. when using PAE > paging or shadowing 2/3/4-level page tables with 4/5-level, and so root_hpa > will be valid but won't be backed by a shadow page. It's all too easy to > blindly call mmu_free_root_page() on root_hpa, be nice and WARN instead of > crashing KVM and possibly the kernel. > > Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> > --- > arch/x86/kvm/mmu/mmu.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index a67071ac80f3..6ea423b00824 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -3222,6 +3222,8 @@ static void mmu_free_root_page(struct kvm *kvm, hpa_t *root_hpa, > return; > > sp = to_shadow_page(*root_hpa & PT64_BASE_ADDR_MASK); > + if (WARN_ON(!sp)) > + return; > > if (is_tdp_mmu_page(sp)) > kvm_tdp_mmu_put_root(kvm, sp, false); Reviewed-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx> Best regards, Maxim Levitsky
