[PATCH 4/5] arm/arm64: KVM: Don't allow creating VCPUs after vgic_initialized

[Christoffer Dall]

When the vgic initializes its internal state it does so based on the
number of VCPUs available at the time.  If we allow KVM to create more
VCPUs after the VGIC has been initialized, we are likely to error out in
unfortunate ways later, perform buffer overflows etc.

Cc: Eric Auger <eric.auger at linaro.org>
Signed-off-by: Christoffer Dall <christoffer.dall at linaro.org>
---
This replaces Eric Auger's previous patch
(https://lists.cs.columbia.edu/pipermail/kvmarm/2014-December/012646.html),
because it fits better with testing to include it in this series and I
realized that we need to add a check against irqchip_in_kernel() as
well.

 arch/arm/kvm/arm.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index a9d005f..d4da244 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -213,6 +213,11 @@ struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm, unsigned int id)
 	int err;
 	struct kvm_vcpu *vcpu;
 
+	if (irqchip_in_kernel(kvm) && vgic_initialized(kvm)) {
+		err = -EBUSY;
+		goto out;
+	}
+
 	vcpu = kmem_cache_zalloc(kvm_vcpu_cache, GFP_KERNEL);
 	if (!vcpu) {
 		err = -ENOMEM;
-- 
2.1.2.330.g565301e.dirty