[PATCH 05/12] KVM: MMU: avoid NULL-pointer dereference on page freeing bugs

Paolo Bonzini
2022-02-09T17:01:06Z

If kvm_mmu_free_roots encounters a PAE page table where a 64-bit page
table is expected, the result is a NULL pointer dereference. Instead
just WARN and exit.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
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 7b5765ced928..d0f2077bd798 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3201,6 +3201,8 @@ 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);
--
2.31.1