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

[Jan Kiszka <jan.kiszka@web.de>]

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On 2014-01-03 20:00, Marcelo Tosatti wrote:
> 
> 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.

Cannot follow yet. How precisely do we call free_loaded_vmcs twice on
the same loaded_vmcs? I thought the frees triggered by free_nested ->
nested_free_all_saved_vmcss stay away from vmx->loaded_vmcs, no?

Jan

> 
> Switch the order to avoid the problem.
> 
> https://bugzilla.redhat.com/show_bug.cgi?id=1047892
> 
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index da7837e..2efa33f0 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -7332,8 +7332,8 @@ static void vmx_free_vcpu(struct kvm_vcpu *vcpu)
>  	struct vcpu_vmx *vmx = to_vmx(vcpu);
>  
>  	free_vpid(vmx);
> -	free_nested(vmx);
>  	free_loaded_vmcs(vmx->loaded_vmcs);
> +	free_nested(vmx);
>  	kfree(vmx->guest_msrs);
>  	kvm_vcpu_uninit(vcpu);
>  	kmem_cache_free(kvm_vcpu_cache, vmx);
> 



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