Re: [PATCH] KVM: nVMX: Trap unconditionally if msr bitmap access fails

[Gleb Natapov <gleb@redhat.com>]

On Thu, Feb 14, 2013 at 07:46:27PM +0100, Jan Kiszka wrote:
> This avoids basing decisions on uninitialized variables, potentially
> leaking kernel data to the L1 guest.
> 
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Reviewed-by: Gleb Natapov <gleb@redhat.com>

> ---
>  arch/x86/kvm/vmx.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 2633199..81a25de 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -5991,7 +5991,8 @@ static bool nested_vmx_exit_handled_msr(struct kvm_vcpu *vcpu,
>  	/* Then read the msr_index'th bit from this bitmap: */
>  	if (msr_index < 1024*8) {
>  		unsigned char b;
> -		kvm_read_guest(vcpu->kvm, bitmap + msr_index/8, &b, 1);
> +		if (kvm_read_guest(vcpu->kvm, bitmap + msr_index/8, &b, 1))
> +			return 1;
>  		return 1 & (b >> (msr_index & 7));
>  	} else
>  		return 1; /* let L1 handle the wrong parameter */
> -- 
> 1.7.3.4

--
			Gleb.