[PATCH v3 7/8] KVM: x86: Reject fixeds-size Hyper-V hypercalls with non-zero "var_cnt"
From: Sean Christopherson <seanjc@google.com>
Date: 2021-12-07 22:09:55
Also in:
kvm, linux-hyperv, lkml
Subsystem:
kernel virtual machine for x86 (kvm/x86), kvm x86 hyper-v (kvm/hyper-v), the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Sean Christopherson, Paolo Bonzini, Vitaly Kuznetsov, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
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 <seanjc@google.com> --- 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 f33a5e890048..522ccd2f0db4 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c@@ -2250,14 +2250,14 @@ 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; }
@@ -2267,7 +2267,7 @@ 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; }
@@ -2280,14 +2280,14 @@ 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; }
@@ -2308,7 +2308,7 @@ 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; }
--
2.34.1.400.ga245620fadb-goog