From 40421f38f63764cd41b01c17e2a1fbbe08a1515a Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Tue, 7 Dec 2021 22:09:25 +0000 Subject: [PATCH] KVM: x86: Reject fixeds-size Hyper-V hypercalls with non-zero "var_cnt" Reject Hyper-V hypercalls if the guest specifies a non-zero variable size header (var_cnt in KVM) for a hypercall that has a fixed header size. Per the TLFS: It is illegal to specify a non-zero variable header size for a hypercall that is not explicitly documented as accepting variable sized input headers. In such a case the hypercall will result in a return code of HV_STATUS_INVALID_HYPERCALL_INPUT. Note, at least some of the various DEBUG commands likely aren't allowed to use variable size headers, but the TLFS documentation doesn't clearly state what is/isn't allowed. Omit them for now to avoid unnecessary breakage. Signed-off-by: Sean Christopherson Reviewed-by: Vitaly Kuznetsov Message-Id: <20211207220926.718794-8-seanjc@google.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/hyperv.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c index e46f267585f46..acabe9d898cf9 100644 --- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -2253,14 +2253,14 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu) switch (hc.code) { case HVCALL_NOTIFY_LONG_SPIN_WAIT: - if (unlikely(hc.rep)) { + if (unlikely(hc.rep || hc.var_cnt)) { ret = HV_STATUS_INVALID_HYPERCALL_INPUT; break; } kvm_vcpu_on_spin(vcpu, true); break; case HVCALL_SIGNAL_EVENT: - if (unlikely(hc.rep)) { + if (unlikely(hc.rep || hc.var_cnt)) { ret = HV_STATUS_INVALID_HYPERCALL_INPUT; break; } @@ -2270,7 +2270,7 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu) fallthrough; /* maybe userspace knows this conn_id */ case HVCALL_POST_MESSAGE: /* don't bother userspace if it has no way to handle it */ - if (unlikely(hc.rep || !to_hv_synic(vcpu)->active)) { + if (unlikely(hc.rep || hc.var_cnt || !to_hv_synic(vcpu)->active)) { ret = HV_STATUS_INVALID_HYPERCALL_INPUT; break; } @@ -2283,14 +2283,14 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu) kvm_hv_hypercall_complete_userspace; return 0; case HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST: - if (unlikely(!hc.rep_cnt || hc.rep_idx)) { + if (unlikely(!hc.rep_cnt || hc.rep_idx || hc.var_cnt)) { ret = HV_STATUS_INVALID_HYPERCALL_INPUT; break; } ret = kvm_hv_flush_tlb(vcpu, &hc, false); break; case HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE: - if (unlikely(hc.rep)) { + if (unlikely(hc.rep || hc.var_cnt)) { ret = HV_STATUS_INVALID_HYPERCALL_INPUT; break; } @@ -2311,7 +2311,7 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu) ret = kvm_hv_flush_tlb(vcpu, &hc, true); break; case HVCALL_SEND_IPI: - if (unlikely(hc.rep)) { + if (unlikely(hc.rep || hc.var_cnt)) { ret = HV_STATUS_INVALID_HYPERCALL_INPUT; break; }