Re: [Xen-devel] [PATCH 1/3] XSA-60 security hole: disable EPT when !cpu_has_vmx_pat

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.10.13 at 20:33, "Liu, Jinsong" <jinsong.liu@xxxxxxxxx> wrote:
> From 9ec2ca512979e99a229d333038f849a2d5a7fde5 Mon Sep 17 00:00:00 2001
> From: Liu Jinsong <jinsong.liu@xxxxxxxxx>
> Date: Thu, 17 Oct 2013 04:00:49 +0800
> Subject: [PATCH 1/3] XSA-60 security hole: disable EPT when !cpu_has_vmx_pat
> 
> Recently Oracle developers found a Xen security issue as DOS affecting,
> named as XSA-60. Please refer http://xenbits.xen.org/xsa/advisory-60.html 
> Basically it involves how to handle guest cr0.cd setting, which under
> some environment it consumes much time resulting in DOS-like behavior.
> 
> This is a preparing patch for fixing XSA-60. Later patch will fix XSA-60
> via PAT under Intel EPT case, which depends on cpu_has_vmx_pat.
> 
> Signed-off-by: Liu Jinsong <jinsong.liu@xxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

> ---
>  xen/arch/x86/hvm/vmx/vmcs.c |    4 ++--
>  xen/arch/x86/hvm/vmx/vmx.c  |   10 +++++++---
>  2 files changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
> index 6526504..6916c6d 100644
> --- a/xen/arch/x86/hvm/vmx/vmcs.c
> +++ b/xen/arch/x86/hvm/vmx/vmcs.c
> @@ -921,7 +921,7 @@ static int construct_vmcs(struct vcpu *v)
>          vmx_disable_intercept_for_msr(v, MSR_IA32_SYSENTER_CS, MSR_TYPE_R | 
> MSR_TYPE_W);
>          vmx_disable_intercept_for_msr(v, MSR_IA32_SYSENTER_ESP, MSR_TYPE_R 
> | MSR_TYPE_W);
>          vmx_disable_intercept_for_msr(v, MSR_IA32_SYSENTER_EIP, MSR_TYPE_R 
> | MSR_TYPE_W);
> -        if ( cpu_has_vmx_pat && paging_mode_hap(d) )
> +        if ( paging_mode_hap(d) )
>              vmx_disable_intercept_for_msr(v, MSR_IA32_CR_PAT, MSR_TYPE_R | 
> MSR_TYPE_W);
>      }
>  
> @@ -1063,7 +1063,7 @@ static int construct_vmcs(struct vcpu *v)
>          __vmwrite(EPT_POINTER, ept_get_eptp(ept));
>      }
>  
> -    if ( cpu_has_vmx_pat && paging_mode_hap(d) )
> +    if ( paging_mode_hap(d) )
>      {
>          u64 host_pat, guest_pat;
>  
> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
> index 9ca8632..b59bf59 100644
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -908,7 +908,7 @@ static unsigned long vmx_get_shadow_gs_base(struct vcpu 
> *v)
>  
>  static int vmx_set_guest_pat(struct vcpu *v, u64 gpat)
>  {
> -    if ( !cpu_has_vmx_pat || !paging_mode_hap(v->domain) )
> +    if ( !paging_mode_hap(v->domain) )
>          return 0;
>  
>      vmx_vmcs_enter(v);
> @@ -919,7 +919,7 @@ static int vmx_set_guest_pat(struct vcpu *v, u64 gpat)
>  
>  static int vmx_get_guest_pat(struct vcpu *v, u64 *gpat)
>  {
> -    if ( !cpu_has_vmx_pat || !paging_mode_hap(v->domain) )
> +    if ( !paging_mode_hap(v->domain) )
>          return 0;
>  
>      vmx_vmcs_enter(v);
> @@ -1591,7 +1591,11 @@ const struct hvm_function_table * __init 
> start_vmx(void)
>          return NULL;
>      }
>  
> -    if ( cpu_has_vmx_ept )
> +    /*
> +     * Do not enable EPT when (!cpu_has_vmx_pat), to prevent security hole
> +     * which refer to http://xenbits.xen.org/xsa/advisory-60.html 
> +     */
> +    if ( cpu_has_vmx_ept && cpu_has_vmx_pat )
>      {
>          vmx_function_table.hap_supported = 1;
>  
> -- 
> 1.7.1




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