[SRU Trusty] kvm: nVMX: Don't allow L2 to access the hardware CR8

[Stefan Bader]

On 06.06.2018 15:22, Stefan Bader wrote:
> From: Jim Mattson <jmattson at google.com>
> 
> If L1 does not specify the "use TPR shadow" VM-execution control in
> vmcs12, then L0 must specify the "CR8-load exiting" and "CR8-store
> exiting" VM-execution controls in vmcs02. Failure to do so will give
> the L2 VM unrestricted read/write access to the hardware CR8.
> 
> This fixes CVE-2017-12154.
> 
> Signed-off-by: Jim Mattson <jmattson at google.com>
> Reviewed-by: David Hildenbrand <david at redhat.com>
> Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
> 
> CVE-2017-12154
> 
> (backported from commit 51aa68e7d57e3217192d88ce90fd5b8ef29ec94f)
> Signed-off-by: Stefan Bader <stefan.bader at canonical.com>
> ---

Messed up the destination, sorry.

>  arch/x86/kvm/vmx.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 45af82c..6f2d4493 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -7837,6 +7837,14 @@ static void prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
>  	exec_control &= ~CPU_BASED_VIRTUAL_NMI_PENDING;
>  	exec_control &= ~CPU_BASED_TPR_SHADOW;
>  	exec_control |= vmcs12->cpu_based_vm_exec_control;
> +
> +	if (!(exec_control & CPU_BASED_TPR_SHADOW)) {
> +#ifdef CONFIG_X86_64
> +		exec_control |= CPU_BASED_CR8_LOAD_EXITING |
> +				CPU_BASED_CR8_STORE_EXITING;
> +#endif
> +	}
> +
>  	/*
>  	 * Merging of IO and MSR bitmaps not currently supported.
>  	 * Rather, exit every time.
> 


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