kvm: fix page struct leak in handle_vmon

handle_vmon gets a reference on VMXON region page,
but does not release it. Release the reference.

Found by syzkaller; based on a patch by Dmitry.

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
[bwh: Backported to 4.9: use skip_emulated_instruction()]

Gbp-Pq: Topic bugfix/x86
Gbp-Pq: Name kvm-fix-page-struct-leak-in-handle_vmon.patch

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 64774f419c723d7c24e669a5580e22171e75f003..7fef0a96fd54a4d94188802450b46911f2b8ebfc 100644 (file)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6925,14 +6925,20 @@ static int nested_vmx_check_vmptr(struct kvm_vcpu *vcpu, int exit_reason,
                }
 
                page = nested_get_page(vcpu, vmptr);
-               if (page == NULL ||
-                   *(u32 *)kmap(page) != VMCS12_REVISION) {
+               if (page == NULL) {
                        nested_vmx_failInvalid(vcpu);
+                       skip_emulated_instruction(vcpu);
+                       return 1;
+               }
+               if (*(u32 *)kmap(page) != VMCS12_REVISION) {
                        kunmap(page);
+                       nested_release_page_clean(page);
+                       nested_vmx_failInvalid(vcpu);
                        skip_emulated_instruction(vcpu);
                        return 1;
                }
                kunmap(page);
+               nested_release_page_clean(page);
                vmx->nested.vmxon_ptr = vmptr;
                break;
        case EXIT_REASON_VMCLEAR: