Return -1 from the get_walk() helpers if the shadow walk doesn't fill at
least one spte, which can theoretically happen if the walk hits a
not-present PDPTR. Returning the root level in such a case will cause
get_mmio_spte() to return garbage (uninitialized stack data). In
practice, such a scenario should be impossible as KVM shouldn't get a
reserved-bit page fault with a not-present PDPTR.
Note, using mmu->root_level in get_walk() is wrong for other reasons,
too, but that's now a moot point.
Fixes:
95fb5b0258b7 ("kvm: x86/mmu: Support MMIO in the TDP MMU")
Cc: Ben Gardon <bgardon@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <
20201218003139.2167891-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
static int get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes)
{
struct kvm_shadow_walk_iterator iterator;
- int leaf = vcpu->arch.mmu->root_level;
+ int leaf = -1;
u64 spte;
else
leaf = get_walk(vcpu, addr, sptes);
+ if (unlikely(leaf < 0)) {
+ *sptep = 0ull;
+ return reserved;
+ }
+
rsvd_check = &vcpu->arch.mmu->shadow_zero_check;
for (level = root; level >= leaf; level--) {
{
struct tdp_iter iter;
struct kvm_mmu *mmu = vcpu->arch.mmu;
- int leaf = vcpu->arch.mmu->shadow_root_level;
gfn_t gfn = addr >> PAGE_SHIFT;
+ int leaf = -1;
tdp_mmu_for_each_pte(iter, mmu, gfn, gfn + 1) {
leaf = iter.level;