KVM: VMX: fix use after free of vmx->loaded_vmcs

commit 26a865f4aa8e66a6d94958de7656f7f1b03c6c56 upstream.

After free_loaded_vmcs executes, the "loaded_vmcs" structure
is kfreed, and now vmx->loaded_vmcs points to a kfreed area.
Subsequent free_loaded_vmcs then attempts to manipulate
vmx->loaded_vmcs.

Switch the order to avoid the problem.

https://bugzilla.redhat.com/show_bug.cgi?id=1047892

Reviewed-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index aac5ea7..a4f6bda 100644 (file)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6273,8 +6273,8 @@ static void vmx_free_vcpu(struct kvm_vcpu *vcpu)
        struct vcpu_vmx *vmx = to_vmx(vcpu);
 
        free_vpid(vmx);
        struct vcpu_vmx *vmx = to_vmx(vcpu);
 
        free_vpid(vmx);

-       free_nested(vmx);

        free_loaded_vmcs(vmx->loaded_vmcs);
        free_loaded_vmcs(vmx->loaded_vmcs);

+       free_nested(vmx);

        kfree(vmx->guest_msrs);
        kvm_vcpu_uninit(vcpu);
        kmem_cache_free(kvm_vcpu_cache, vmx);
        kfree(vmx->guest_msrs);
        kvm_vcpu_uninit(vcpu);
        kmem_cache_free(kvm_vcpu_cache, vmx);