From 671ddc700fd08b94967b1e2a937020e30c838609 Mon Sep 17 00:00:00 2001 From: Jim Mattson Date: Tue, 15 Oct 2019 10:44:05 -0700 Subject: KVM: nVMX: Don't leak L1 MMIO regions to L2 If the "virtualize APIC accesses" VM-execution control is set in the VMCS, the APIC virtualization hardware is triggered when a page walk in VMX non-root mode terminates at a PTE wherein the address of the 4k page frame matches the APIC-access address specified in the VMCS. On hardware, the APIC-access address may be any valid 4k-aligned physical address. KVM's nVMX implementation enforces the additional constraint that the APIC-access address specified in the vmcs12 must be backed by a "struct page" in L1. If not, L0 will simply clear the "virtualize APIC accesses" VM-execution control in the vmcs02. The problem with this approach is that the L1 guest has arranged the vmcs12 EPT tables--or shadow page tables, if the "enable EPT" VM-execution control is clear in the vmcs12--so that the L2 guest physical address(es)--or L2 guest linear address(es)--that reference the L2 APIC map to the APIC-access address specified in the vmcs12. Without the "virtualize APIC accesses" VM-execution control in the vmcs02, the APIC accesses in the L2 guest will directly access the APIC-access page in L1. When there is no mapping whatsoever for the APIC-access address in L1, the L2 VM just loses the intended APIC virtualization. However, when the APIC-access address is mapped to an MMIO region in L1, the L2 guest gets direct access to the L1 MMIO device. For example, if the APIC-access address specified in the vmcs12 is 0xfee00000, then L2 gets direct access to L1's APIC. Since this vmcs12 configuration is something that KVM cannot faithfully emulate, the appropriate response is to exit to userspace with KVM_INTERNAL_ERROR_EMULATION. Fixes: fe3ef05c7572 ("KVM: nVMX: Prepare vmcs02 from vmcs01 and vmcs12") Reported-by: Dan Cross Signed-off-by: Jim Mattson Reviewed-by: Peter Shier Reviewed-by: Sean Christopherson Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx/nested.h | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) (limited to 'arch/x86/kvm/vmx/nested.h') diff --git a/arch/x86/kvm/vmx/nested.h b/arch/x86/kvm/vmx/nested.h index 187d39bf0bf1..6280f33e5fa6 100644 --- a/arch/x86/kvm/vmx/nested.h +++ b/arch/x86/kvm/vmx/nested.h @@ -6,6 +6,16 @@ #include "vmcs12.h" #include "vmx.h" +/* + * Status returned by nested_vmx_enter_non_root_mode(): + */ +enum nvmx_vmentry_status { + NVMX_VMENTRY_SUCCESS, /* Entered VMX non-root mode */ + NVMX_VMENTRY_VMFAIL, /* Consistency check VMFail */ + NVMX_VMENTRY_VMEXIT, /* Consistency check VMExit */ + NVMX_VMENTRY_KVM_INTERNAL_ERROR,/* KVM internal error */ +}; + void vmx_leave_nested(struct kvm_vcpu *vcpu); void nested_vmx_setup_ctls_msrs(struct nested_vmx_msrs *msrs, u32 ept_caps, bool apicv); @@ -13,7 +23,8 @@ void nested_vmx_hardware_unsetup(void); __init int nested_vmx_hardware_setup(int (*exit_handlers[])(struct kvm_vcpu *)); void nested_vmx_vcpu_setup(void); void nested_vmx_free_vcpu(struct kvm_vcpu *vcpu); -int nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu, bool from_vmentry); +enum nvmx_vmentry_status nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu, + bool from_vmentry); bool nested_vmx_exit_reflected(struct kvm_vcpu *vcpu, u32 exit_reason); void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason, u32 exit_intr_info, unsigned long exit_qualification); -- cgit v1.2.3