KVM: x86: verify MTRR/PAT validity

KVM: x86: verify MTRR/PAT validity

[Marcelo Tosatti]

Do not allow invalid MTRR/PAT values in set_msr_mtrr.

Please review carefully.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>


Index: kvm/arch/x86/kvm/x86.c
===================================================================
--- kvm.orig/arch/x86/kvm/x86.c
+++ kvm/arch/x86/kvm/x86.c
@@ -722,11 +722,53 @@ static bool msr_mtrr_valid(unsigned msr)
 	return false;
 }
 
+static unsigned mtrr_types[] = {0, 1, 4, 5, 6};
+static unsigned pat_types[] = {0, 1, 4, 5, 6, 7};
+
+static bool valid_mt(unsigned type, int len, unsigned array[len])
+{
+	int i;
+
+	for (i = 0; i < len; i++)
+		if (type == array[i])
+			return true;
+
+	return false;
+}
+
+#define valid_pat_type(a) valid_mt(a, ARRAY_SIZE(pat_types), pat_types)
+#define valid_mtrr_type(a) valid_mt(a, ARRAY_SIZE(mtrr_types), mtrr_types)
+
+static bool mtrr_valid(u32 msr, u64 data)
+{
+	int i;
+
+	if (!msr_mtrr_valid(msr))
+		return false;
+
+	if (msr == MSR_IA32_CR_PAT) {
+		for (i = 0; i < 8; i++)
+			if (!valid_pat_type((data >> (i * 8)) & 0xff))
+				return false;
+		return true;
+	} else if (msr == MSR_MTRRdefType) {
+		return valid_mtrr_type(data & 0xff);
+	} else if (msr >= MSR_MTRRfix64K_00000 && msr <= MSR_MTRRfix4K_F8000) {
+		for (i = 0; i < 8 ; i++)
+			if (!valid_mtrr_type((data >> (i * 8)) & 0xff))
+				return false;
+		return true;
+	}
+
+	/* variable MTRRs, physmaskn have bits 0-10 reserved */
+	return valid_mtrr_type(data & 0xff);
+}
+
 static int set_msr_mtrr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 {
 	u64 *p = (u64 *)&vcpu->arch.mtrr_state.fixed_ranges;
 
-	if (!msr_mtrr_valid(msr))
+	if (!mtrr_valid(msr, data))
 		return 1;
 
 	if (msr == MSR_MTRRdefType) {

Re: KVM: x86: verify MTRR/PAT validity

[Yang, Sheng]

On Tuesday 16 June 2009 20:05:29 Marcelo Tosatti wrote:
> Do not allow invalid MTRR/PAT values in set_msr_mtrr.
>
> Please review carefully.
>
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
>
Looks fine to me.

Is it necessary to check reserved bit of MSR_MTRRdefType and variable MTRRs as 
well? Maybe like this:

if (msr == MSR_MTRRdefType) {
	return valid_mtrr_type(data & ~0xc00ull);
}

And variable ones can be:

#define MTRR_VALID_MASK(v, msr) (~(rsvd_bits(cpuid_max_physaddr(v)) | ((msr % 
2) << 11)))

return valid_mtrr_type(data & MTRR_VALID_MASK(vcpu, msr)))


(rsvd_bits() is in mmu.c, both untested)

Maybe we can put cpuid_max_physaddr as a field in vcpu struct?

-- 
regards
Yang, Sheng

>
> Index: kvm/arch/x86/kvm/x86.c
> ===================================================================
> --- kvm.orig/arch/x86/kvm/x86.c
> +++ kvm/arch/x86/kvm/x86.c
> @@ -722,11 +722,53 @@ static bool msr_mtrr_valid(unsigned msr)
>  	return false;
>  }
>
> +static unsigned mtrr_types[] = {0, 1, 4, 5, 6};
> +static unsigned pat_types[] = {0, 1, 4, 5, 6, 7};
> +
> +static bool valid_mt(unsigned type, int len, unsigned array[len])
> +{
> +	int i;
> +
> +	for (i = 0; i < len; i++)
> +		if (type == array[i])
> +			return true;
> +
> +	return false;
> +}
> +
> +#define valid_pat_type(a) valid_mt(a, ARRAY_SIZE(pat_types), pat_types)
> +#define valid_mtrr_type(a) valid_mt(a, ARRAY_SIZE(mtrr_types), mtrr_types)
> +
> +static bool mtrr_valid(u32 msr, u64 data)
> +{
> +	int i;
> +
> +	if (!msr_mtrr_valid(msr))
> +		return false;
> +
> +	if (msr == MSR_IA32_CR_PAT) {
> +		for (i = 0; i < 8; i++)
> +			if (!valid_pat_type((data >> (i * 8)) & 0xff))
> +				return false;
> +		return true;
> +	} else if (msr == MSR_MTRRdefType) {
> +		return valid_mtrr_type(data & 0xff);
> +	} else if (msr >= MSR_MTRRfix64K_00000 && msr <= MSR_MTRRfix4K_F8000) {
> +		for (i = 0; i < 8 ; i++)
> +			if (!valid_mtrr_type((data >> (i * 8)) & 0xff))
> +				return false;
> +		return true;
> +	}
> +
> +	/* variable MTRRs, physmaskn have bits 0-10 reserved */
> +	return valid_mtrr_type(data & 0xff);
> +}
> +
>  static int set_msr_mtrr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
>  {
>  	u64 *p = (u64 *)&vcpu->arch.mtrr_state.fixed_ranges;
>
> -	if (!msr_mtrr_valid(msr))
> +	if (!mtrr_valid(msr, data))
>  		return 1;
>
>  	if (msr == MSR_MTRRdefType) {

Re: KVM: x86: verify MTRR/PAT validity

[Avi Kivity]

On 06/16/2009 03:05 PM, Marcelo Tosatti wrote:
> Do not allow invalid MTRR/PAT values in set_msr_mtrr.
>
> Please review carefully.
>
> Signed-off-by: Marcelo Tosatti<mtosatti@redhat.com>
>
>
> +static unsigned mtrr_types[] = {0, 1, 4, 5, 6};
> +static unsigned pat_types[] = {0, 1, 4, 5, 6, 7};
> +
> +static bool valid_mt(unsigned type, int len, unsigned array[len])
> +{
> +	int i;
> +
> +	for (i = 0; i<  len; i++)
> +		if (type == array[i])
> +			return true;
> +
> +	return false;
> +}
> +
> +#define valid_pat_type(a) valid_mt(a, ARRAY_SIZE(pat_types), pat_types)
> +#define valid_mtrr_type(a) valid_mt(a, ARRAY_SIZE(mtrr_types), mtrr_types)
> +
>    

A little pointless since this is so performance-insensitive, but still:

valid_pat_type(t)
{
     return t < 8 && (1 << t) & 0xf3; /* 0, 1, 4, 5, 6, 7 */
}

valid_mtrr_type(t)
{
     return t < 8 && (1 << t) & 0x73; /* 0, 1, 4, 5, 6 */
}

-- 
error compiling committee.c: too many arguments to function

Re: KVM: x86: verify MTRR/PAT validity

[Marcelo Tosatti]

On Thu, Jun 18, 2009 at 10:39:32AM +0800, Yang, Sheng wrote:
> On Tuesday 16 June 2009 20:05:29 Marcelo Tosatti wrote:
> > Do not allow invalid MTRR/PAT values in set_msr_mtrr.
> >
> > Please review carefully.
> >
> > Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> >
> Looks fine to me.
> 
> Is it necessary to check reserved bit of MSR_MTRRdefType and variable MTRRs as 
> well? Maybe like this:
> 
> if (msr == MSR_MTRRdefType) {
> 	return valid_mtrr_type(data & ~0xc00ull);
> }
> 
> And variable ones can be:
> 
> #define MTRR_VALID_MASK(v, msr) (~(rsvd_bits(cpuid_max_physaddr(v)) | ((msr % 
> 2) << 11)))
> 
> return valid_mtrr_type(data & MTRR_VALID_MASK(vcpu, msr)))
> 
> 
> (rsvd_bits() is in mmu.c, both untested)
> 
> Maybe we can put cpuid_max_physaddr as a field in vcpu struct?

Sheng,

This in the BIOS is writing 1's into the reserved address bits into
variable MTRR:

    wrmsr_smp(MTRRphysMask_MSR(0), ~(0x20000000ull - 1) | 0x800);

So i'll leave just memory type validity checking and MSR_MTRRdefType 
valid bit checks in for now:




KVM: x86: verify MTRR/PAT validity

Do not allow invalid memory types in MTRR/PAT (generating a #GP
otherwise).

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>



Index: kvm/arch/x86/kvm/x86.c
===================================================================
--- kvm.orig/arch/x86/kvm/x86.c
+++ kvm/arch/x86/kvm/x86.c
@@ -721,11 +721,48 @@ static bool msr_mtrr_valid(unsigned msr)
 	return false;
 }
 
+static bool valid_pat_type(unsigned t)
+{
+	return t < 8 && (1 << t) & 0xf3; /* 0, 1, 4, 5, 6, 7 */
+}
+
+static bool valid_mtrr_type(unsigned t)
+{
+	return t < 8 && (1 << t) & 0x73; /* 0, 1, 4, 5, 6 */
+}
+
+static bool mtrr_valid(struct kvm_vcpu *vcpu, u32 msr, u64 data)
+{
+	int i;
+
+	if (!msr_mtrr_valid(msr))
+		return false;
+
+	if (msr == MSR_IA32_CR_PAT) {
+		for (i = 0; i < 8; i++)
+			if (!valid_pat_type((data >> (i * 8)) & 0xff))
+				return false;
+		return true;
+	} else if (msr == MSR_MTRRdefType) {
+		if (data & ~0xcff)
+			return false;
+		return valid_mtrr_type(data & 0xff);
+	} else if (msr >= MSR_MTRRfix64K_00000 && msr <= MSR_MTRRfix4K_F8000) {
+		for (i = 0; i < 8 ; i++)
+			if (!valid_mtrr_type((data >> (i * 8)) & 0xff))
+				return false;
+		return true;
+	}
+
+	/* variable MTRRs */
+	return valid_mtrr_type(data & 0xff);
+}
+
 static int set_msr_mtrr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 {
 	u64 *p = (u64 *)&vcpu->arch.mtrr_state.fixed_ranges;
 
-	if (!msr_mtrr_valid(msr))
+	if (!mtrr_valid(vcpu, msr, data))
 		return 1;
 
 	if (msr == MSR_MTRRdefType) {

Re: KVM: x86: verify MTRR/PAT validity

[Avi Kivity]

On 06/22/2009 09:27 PM, Marcelo Tosatti wrote:
>
> This in the BIOS is writing 1's into the reserved address bits into
> variable MTRR:
>
>      wrmsr_smp(MTRRphysMask_MSR(0), ~(0x20000000ull - 1) | 0x800);
>
> So i'll leave just memory type validity checking and MSR_MTRRdefType
> valid bit checks in for now:
>    
Applied, thanks.

-- 
error compiling committee.c: too many arguments to function