diff options
| author |   Paolo Bonzini <pbonzini@redhat.com> | 2022-02-08 19:08:33 -0500 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2022-02-25 08:20:16 -0500 |
| commit | 9191b8f0745e63edf519e4a54a4aaae1d3d46fbd (patch) | |
| tree | 7aa9914ac9413de4325d71eee3a6bee663189e9d | |
| parent | KVM: x86: do not deliver asynchronous page faults if CR0.PG=0 (diff) | |
KVM: x86/mmu: avoid NULL-pointer dereference on page freeing bugs
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.
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
| -rw-r--r-- | arch/x86/kvm/mmu/mmu.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 0620480b99e0..28c4d658d2ac 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -3206,6 +3206,8 @@ 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); |