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KVM: nVMX: check for required but missing VMCS12 in KVM_SET_NESTED_STATE 

A missing VMCS12 was not causing -EINVAL (it was just read with
copy_from_user, so it is not a security issue, but it is still
wrong).  Test for VMCS12 validity and reject the nested state
if a VMCS12 is required but not present.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2020-07-27 09:00:37 -04:00
parent 9319676595
commit 0f02bd0ade
3 changed files with 26 additions and 4 deletions
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13
arch/x86/kvm/vmx/nested.c
View File

@ -6108,9 +6108,16 @@ static int vmx_set_nested_state(struct kvm_vcpu *vcpu,
if (ret)
return ret;
/* Empty 'VMXON' state is permitted */
if (kvm_state->size < sizeof(*kvm_state) + sizeof(*vmcs12))
return 0;
/* Empty 'VMXON' state is permitted if no VMCS loaded */
if (kvm_state->size < sizeof(*kvm_state) + sizeof(*vmcs12)) {
/* See vmx_has_valid_vmcs12. */
if ((kvm_state->flags & KVM_STATE_NESTED_GUEST_MODE) ||
(kvm_state->flags & KVM_STATE_NESTED_EVMCS) ||
(kvm_state->hdr.vmx.vmcs12_pa != -1ull))
return -EINVAL;
else
return 0;
}
if (kvm_state->hdr.vmx.vmcs12_pa != -1ull) {
if (kvm_state->hdr.vmx.vmcs12_pa == kvm_state->hdr.vmx.vmxon_pa ||

5
arch/x86/kvm/vmx/nested.h
View File

@ -47,6 +47,11 @@ static inline struct vmcs12 *get_shadow_vmcs12(struct kvm_vcpu *vcpu)
return to_vmx(vcpu)->nested.cached_shadow_vmcs12;
}
/*
* Note: the same condition is checked against the state provided by userspace
* in vmx_set_nested_state; if it is satisfied, the nested state must include
* the VMCS12.
*/
static inline int vmx_has_valid_vmcs12(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);

12
tools/testing/selftests/kvm/x86_64/vmx_set_nested_state_test.c
View File

@ -183,9 +183,19 @@ void test_vmx_nested_state(struct kvm_vm *vm)
state->hdr.vmx.smm.flags = KVM_STATE_NESTED_SMM_GUEST_MODE;
test_nested_state_expect_einval(vm, state);
/* Size must be large enough to fit kvm_nested_state and vmcs12. */
/*
* Size must be large enough to fit kvm_nested_state and vmcs12
* if VMCS12 physical address is set
*/
set_default_vmx_state(state, state_sz);
state->size = sizeof(*state);
state->flags = 0;
test_nested_state_expect_einval(vm, state);
set_default_vmx_state(state, state_sz);
state->size = sizeof(*state);
state->flags = 0;
state->hdr.vmx.vmcs12_pa = -1;
test_nested_state(vm, state);
/*