[PATCH 5.19 0033/1157] KVM: nVMX: Let userspace set nVMX MSR to any _host_ supported value

Greg Kroah-Hartman
2022-08-15T21:53:28Z

From: Sean Christopherson <seanjc@google.com>

commit f8ae08f9789ad59d318ea75b570caa454aceda81 upstream.

Restrict the nVMX MSRs based on KVM's config, not based on the guest's
current config. Using the guest's config to audit the new config
prevents userspace from restoring the original config (KVM's config) if
at any point in the past the guest's config was restricted in any way.

Fixes: 62cc6b9dc61e ("KVM: nVMX: support restore of VMX capability MSRs")
Cc: stable@vger.kernel.org
Cc: David Matlack <dmatlack@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220607213604.3346000-6-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/kvm/vmx/nested.c | 70 ++++++++++++++++++++++++----------------------
1 file changed, 37 insertions(+), 33 deletions(-)

--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -1223,7 +1223,7 @@ static int vmx_restore_vmx_basic(struct
BIT_ULL(49) | BIT_ULL(54) | BIT_ULL(55) |
/* reserved */
BIT_ULL(31) | GENMASK_ULL(47, 45) | GENMASK_ULL(63, 56);
- u64 vmx_basic = vmx->nested.msrs.basic;
+ u64 vmx_basic = vmcs_config.nested.basic;

if (!is_bitwise_subset(vmx_basic, data, feature_and_reserved))
return -EINVAL;
@@ -1246,36 +1246,42 @@ static int vmx_restore_vmx_basic(struct
return 0;
}

-static int
-vmx_restore_control_msr(struct vcpu_vmx *vmx, u32 msr_index, u64 data)
+static void vmx_get_control_msr(struct nested_vmx_msrs *msrs, u32 msr_index,
+ u32 **low, u32 **high)
{
- u64 supported;
- u32 *lowp, *highp;
-
switch (msr_index) {
case MSR_IA32_VMX_TRUE_PINBASED_CTLS:
- lowp = &vmx->nested.msrs.pinbased_ctls_low;
- highp = &vmx->nested.msrs.pinbased_ctls_high;
+ *low = &msrs->pinbased_ctls_low;
+ *high = &msrs->pinbased_ctls_high;
break;
case MSR_IA32_VMX_TRUE_PROCBASED_CTLS:
- lowp = &vmx->nested.msrs.procbased_ctls_low;
- highp = &vmx->nested.msrs.procbased_ctls_high;
+ *low = &msrs->procbased_ctls_low;
+ *high = &msrs->procbased_ctls_high;
break;
case MSR_IA32_VMX_TRUE_EXIT_CTLS:
- lowp = &vmx->nested.msrs.exit_ctls_low;
- highp = &vmx->nested.msrs.exit_ctls_high;
+ *low = &msrs->exit_ctls_low;
+ *high = &msrs->exit_ctls_high;
break;
case MSR_IA32_VMX_TRUE_ENTRY_CTLS:
- lowp = &vmx->nested.msrs.entry_ctls_low;
- highp = &vmx->nested.msrs.entry_ctls_high;
+ *low = &msrs->entry_ctls_low;
+ *high = &msrs->entry_ctls_high;
break;
case MSR_IA32_VMX_PROCBASED_CTLS2:
- lowp = &vmx->nested.msrs.secondary_ctls_low;
- highp = &vmx->nested.msrs.secondary_ctls_high;
+ *low = &msrs->secondary_ctls_low;
+ *high = &msrs->secondary_ctls_high;
break;
default:
BUG();
}
+}
+
+static int
+vmx_restore_control_msr(struct vcpu_vmx *vmx, u32 msr_index, u64 data)
+{
+ u32 *lowp, *highp;
+ u64 supported;
+
+ vmx_get_control_msr(&vmcs_config.nested, msr_index, &lowp, &highp);

supported = vmx_control_msr(*lowp, *highp);

@@ -1287,6 +1293,7 @@ vmx_restore_control_msr(struct vcpu_vmx
if (!is_bitwise_subset(supported, data, GENMASK_ULL(63, 32)))
return -EINVAL;

+ vmx_get_control_msr(&vmx->nested.msrs, msr_index, &lowp, &highp);
*lowp = data;
*highp = data >> 32;
return 0;
@@ -1300,10 +1307,8 @@ static int vmx_restore_vmx_misc(struct v
BIT_ULL(28) | BIT_ULL(29) | BIT_ULL(30) |
/* reserved */
GENMASK_ULL(13, 9) | BIT_ULL(31);
- u64 vmx_misc;
-
- vmx_misc = vmx_control_msr(vmx->nested.msrs.misc_low,
- vmx->nested.msrs.misc_high);
+ u64 vmx_misc = vmx_control_msr(vmcs_config.nested.misc_low,
+ vmcs_config.nested.misc_high);

if (!is_bitwise_subset(vmx_misc, data, feature_and_reserved_bits))
return -EINVAL;
@@ -1331,10 +1336,8 @@ static int vmx_restore_vmx_misc(struct v

static int vmx_restore_vmx_ept_vpid_cap(struct vcpu_vmx *vmx, u64 data)
{
- u64 vmx_ept_vpid_cap;
-
- vmx_ept_vpid_cap = vmx_control_msr(vmx->nested.msrs.ept_caps,
- vmx->nested.msrs.vpid_caps);
+ u64 vmx_ept_vpid_cap = vmx_control_msr(vmcs_config.nested.ept_caps,
+ vmcs_config.nested.vpid_caps);

/* Every bit is either reserved or a feature bit. */
if (!is_bitwise_subset(vmx_ept_vpid_cap, data, -1ULL))
@@ -1345,20 +1348,21 @@ static int vmx_restore_vmx_ept_vpid_cap(
return 0;
}

-static int vmx_restore_fixed0_msr(struct vcpu_vmx *vmx, u32 msr_index, u64 data)
+static u64 *vmx_get_fixed0_msr(struct nested_vmx_msrs *msrs, u32 msr_index)
{
- u64 *msr;
-
switch (msr_index) {
case MSR_IA32_VMX_CR0_FIXED0:
- msr = &vmx->nested.msrs.cr0_fixed0;
- break;
+ return &msrs->cr0_fixed0;
case MSR_IA32_VMX_CR4_FIXED0:
- msr = &vmx->nested.msrs.cr4_fixed0;
- break;
+ return &msrs->cr4_fixed0;
default:
BUG();
}
+}
+
+static int vmx_restore_fixed0_msr(struct vcpu_vmx *vmx, u32 msr_index, u64 data)
+{
+ const u64 *msr = vmx_get_fixed0_msr(&vmcs_config.nested, msr_index);

/*
* 1 bits (which indicates bits which "must-be-1" during VMX operation)
@@ -1367,7 +1371,7 @@ static int vmx_restore_fixed0_msr(struct
if (!is_bitwise_subset(data, *msr, -1ULL))
return -EINVAL;

- *msr = data;
+ *vmx_get_fixed0_msr(&vmx->nested.msrs, msr_index) = data;
return 0;
}

@@ -1428,7 +1432,7 @@ int vmx_set_vmx_msr(struct kvm_vcpu *vcp
vmx->nested.msrs.vmcs_enum = data;
return 0;
case MSR_IA32_VMX_VMFUNC:
- if (data & ~vmx->nested.msrs.vmfunc_controls)
+ if (data & ~vmcs_config.nested.vmfunc_controls)
return -EINVAL;
vmx->nested.msrs.vmfunc_controls = data;
return 0;