[v3,02/37] KVM: nVMX: Validate the EPTP when emulating INVEPT(EXTENT_CONTEXT)
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Message ID 20200320212833.3507-3-sean.j.christopherson@intel.com
State New
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Series
  • KVM: x86: TLB flushing fixes and enhancements
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Commit Message

Sean Christopherson March 20, 2020, 9:27 p.m. UTC
Signal VM-Fail for the single-context variant of INVEPT if the specified
EPTP is invalid.  Per the INEVPT pseudocode in Intel's SDM, it's subject
to the standard EPT checks:

  If VM entry with the "enable EPT" VM execution control set to 1 would
  fail due to the EPTP value then VMfail(Invalid operand to INVEPT/INVVPID);

Fixes: bfd0a56b90005 ("nEPT: Nested INVEPT")
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
 arch/x86/kvm/vmx/nested.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

Comments

Vitaly Kuznetsov March 23, 2020, 2:51 p.m. UTC | #1
Sean Christopherson <sean.j.christopherson@intel.com> writes:

> Signal VM-Fail for the single-context variant of INVEPT if the specified
> EPTP is invalid.  Per the INEVPT pseudocode in Intel's SDM, it's subject
> to the standard EPT checks:
>
>   If VM entry with the "enable EPT" VM execution control set to 1 would
>   fail due to the EPTP value then VMfail(Invalid operand to INVEPT/INVVPID);
>
> Fixes: bfd0a56b90005 ("nEPT: Nested INVEPT")
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> ---
>  arch/x86/kvm/vmx/nested.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index 8578513907d7..f3774cef4fd4 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -5156,8 +5156,12 @@ static int handle_invept(struct kvm_vcpu *vcpu)
>  	}
>  
>  	switch (type) {
> -	case VMX_EPT_EXTENT_GLOBAL:
>  	case VMX_EPT_EXTENT_CONTEXT:
> +		if (!nested_vmx_check_eptp(vcpu, operand.eptp))
> +			return nested_vmx_failValid(vcpu,
> +				VMXERR_INVALID_OPERAND_TO_INVEPT_INVVPID);

I was going to ask "and we don't seem to check that current nested VMPTR
is valid, how can we know that nested_vmx_failValid() is the right
VMfail() to use" but then I checked our nested_vmx_failValid() and there
is a fallback there:

	if (vmx->nested.current_vmptr == -1ull && !vmx->nested.hv_evmcs)
		return nested_vmx_failInvalid(vcpu);

so this is a non-issue. My question, however, transforms into "would it
make sense to introduce nested_vmx_fail() implementing the logic from
SDM:

VMfail(ErrorNumber):
	IF VMCS pointer is valid
		THEN VMfailValid(ErrorNumber);
	ELSE VMfailInvalid;
	FI;

to assist an innocent reader of the code?"

> +		fallthrough;
> +	case VMX_EPT_EXTENT_GLOBAL:
>  	/*
>  	 * TODO: Sync the necessary shadow EPT roots here, rather than
>  	 * at the next emulated VM-entry.

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Sean Christopherson March 23, 2020, 3:45 p.m. UTC | #2
On Mon, Mar 23, 2020 at 03:51:17PM +0100, Vitaly Kuznetsov wrote:
> Sean Christopherson <sean.j.christopherson@intel.com> writes:
> 
> > Signal VM-Fail for the single-context variant of INVEPT if the specified
> > EPTP is invalid.  Per the INEVPT pseudocode in Intel's SDM, it's subject
> > to the standard EPT checks:
> >
> >   If VM entry with the "enable EPT" VM execution control set to 1 would
> >   fail due to the EPTP value then VMfail(Invalid operand to INVEPT/INVVPID);
> >
> > Fixes: bfd0a56b90005 ("nEPT: Nested INVEPT")
> > Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> > ---
> >  arch/x86/kvm/vmx/nested.c | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> > index 8578513907d7..f3774cef4fd4 100644
> > --- a/arch/x86/kvm/vmx/nested.c
> > +++ b/arch/x86/kvm/vmx/nested.c
> > @@ -5156,8 +5156,12 @@ static int handle_invept(struct kvm_vcpu *vcpu)
> >  	}
> >  
> >  	switch (type) {
> > -	case VMX_EPT_EXTENT_GLOBAL:
> >  	case VMX_EPT_EXTENT_CONTEXT:
> > +		if (!nested_vmx_check_eptp(vcpu, operand.eptp))
> > +			return nested_vmx_failValid(vcpu,
> > +				VMXERR_INVALID_OPERAND_TO_INVEPT_INVVPID);
> 
> I was going to ask "and we don't seem to check that current nested VMPTR
> is valid, how can we know that nested_vmx_failValid() is the right
> VMfail() to use" but then I checked our nested_vmx_failValid() and there
> is a fallback there:
> 
> 	if (vmx->nested.current_vmptr == -1ull && !vmx->nested.hv_evmcs)
> 		return nested_vmx_failInvalid(vcpu);
> 
> so this is a non-issue. My question, however, transforms into "would it
> make sense to introduce nested_vmx_fail() implementing the logic from
> SDM:
> 
> VMfail(ErrorNumber):
> 	IF VMCS pointer is valid
> 		THEN VMfailValid(ErrorNumber);
> 	ELSE VMfailInvalid;
> 	FI;
> 

Hmm, I wouldn't be opposed to such a wrapper.  It would pair with
nested_vmx_succeed().

> 
> > +		fallthrough;
> > +	case VMX_EPT_EXTENT_GLOBAL:
> >  	/*
> >  	 * TODO: Sync the necessary shadow EPT roots here, rather than
> >  	 * at the next emulated VM-entry.
> 
> Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> 
> -- 
> Vitaly
>
Paolo Bonzini March 23, 2020, 11:46 p.m. UTC | #3
On 23/03/20 16:45, Sean Christopherson wrote:
>> My question, however, transforms into "would it
>> make sense to introduce nested_vmx_fail() implementing the logic from
>> SDM:
>>
>> VMfail(ErrorNumber):
>> 	IF VMCS pointer is valid
>> 		THEN VMfailValid(ErrorNumber);
>> 	ELSE VMfailInvalid;
>> 	FI;
>>
> Hmm, I wouldn't be opposed to such a wrapper.  It would pair with
> nested_vmx_succeed().
> 

Neither would I.

Paolo

Patch
diff mbox series

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 8578513907d7..f3774cef4fd4 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -5156,8 +5156,12 @@  static int handle_invept(struct kvm_vcpu *vcpu)
 	}
 
 	switch (type) {
-	case VMX_EPT_EXTENT_GLOBAL:
 	case VMX_EPT_EXTENT_CONTEXT:
+		if (!nested_vmx_check_eptp(vcpu, operand.eptp))
+			return nested_vmx_failValid(vcpu,
+				VMXERR_INVALID_OPERAND_TO_INVEPT_INVVPID);
+		fallthrough;
+	case VMX_EPT_EXTENT_GLOBAL:
 	/*
 	 * TODO: Sync the necessary shadow EPT roots here, rather than
 	 * at the next emulated VM-entry.