From: Oliver Upton Date: Tue, 4 Feb 2020 15:26:31 -0800 Subject: KVM: nVMX: Check IO instruction VM-exit conditions Git-commit: 35a571346a94fb93b5b3b6a599675ef3384bc75c References: CVE-2020-2732 bsc#1163971 Patch-mainline: v5.6-rc4 Consult the 'unconditional IO exiting' and 'use IO bitmaps' VM-execution controls when checking instruction interception. If the 'use IO bitmaps' VM-execution control is 1, check the instruction access against the IO bitmaps to determine if the instruction causes a VM-exit. Signed-off-by: Oliver Upton Signed-off-by: Paolo Bonzini Acked-by: Joerg Roedel --- arch/x86/kvm/vmx/nested.c | 2 +- arch/x86/kvm/vmx/vmx.c | 57 ++++++++++++++++++++++++++++++++++++++++++----- 2 files changed, 52 insertions(+), 7 deletions(-) --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -8570,7 +8570,7 @@ static bool nested_vmx_exit_handled_io(s struct vmcs12 *vmcs12) { unsigned long exit_qualification; - unsigned int port; + unsigned short port; int size; if (!nested_cpu_has(vmcs12, CPU_BASED_USE_IO_BITMAPS)) @@ -12386,10 +12386,55 @@ static void nested_vmx_entry_failure(str to_vmx(vcpu)->nested.sync_shadow_vmcs = true; } +static int vmx_check_intercept_io(struct kvm_vcpu *vcpu, + struct x86_instruction_info *info) +{ + struct vmcs12 *vmcs12 = get_vmcs12(vcpu); + unsigned short port; + bool intercept; + int size; + + if (info->intercept == x86_intercept_in || + info->intercept == x86_intercept_ins) { + port = info->src_val; + size = info->dst_bytes; + } else { + port = info->dst_val; + size = info->src_bytes; + } + + /* + * If the 'use IO bitmaps' VM-execution control is 0, IO instruction + * VM-exits depend on the 'unconditional IO exiting' VM-execution + * control. + * + * Otherwise, IO instruction VM-exits are controlled by the IO bitmaps. + */ + if (!nested_cpu_has(vmcs12, CPU_BASED_USE_IO_BITMAPS)) + intercept = nested_cpu_has(vmcs12, + CPU_BASED_UNCOND_IO_EXITING); + else + intercept = nested_vmx_check_io_bitmaps(vcpu, port, size); + + return intercept ? X86EMUL_UNHANDLEABLE : X86EMUL_CONTINUE; +} + static int vmx_check_intercept(struct kvm_vcpu *vcpu, struct x86_instruction_info *info, enum x86_intercept_stage stage) { + switch (info->intercept) { + case x86_intercept_in: + case x86_intercept_ins: + case x86_intercept_out: + case x86_intercept_outs: + return vmx_check_intercept_io(vcpu, info); + + /* TODO: check more intercepts... */ + default: + break; + } + return X86EMUL_UNHANDLEABLE; }