KVM: Ensure all vcpus are consistent with in-kernel irqchip settings

If some vcpus are created before KVM_CREATE_IRQCHIP, then
irqchip_in_kernel() and vcpu->arch.apic will be inconsistent, leading
to potential NULL pointer dereferences.

Fix by:
- ensuring that no vcpus are installed when KVM_CREATE_IRQCHIP is called
- ensuring that a vcpu has an apic if it is installed after KVM_CREATE_IRQCHIP

This is somewhat long winded because vcpu->arch.apic is created without
kvm->lock held.

Based on earlier patch by Michael Ellerman.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Avi Kivity <avi@redhat.com>

diff --git a/arch/ia64/kvm/kvm-ia64.c b/arch/ia64/kvm/kvm-ia64.c
index d8ddbba6fe7de9ed8c55a65a3d1dd7ab8104908e..f5104b7c52cd369b0150f9884133922ba6defe03 100644 (file)
--- a/arch/ia64/kvm/kvm-ia64.c
+++ b/arch/ia64/kvm/kvm-ia64.c
@@ -1172,6 +1172,11 @@ out:
 
 #define PALE_RESET_ENTRY    0x80000000ffffffb0UL
 
+bool kvm_vcpu_compatible(struct kvm_vcpu *vcpu)
+{
+       return irqchip_in_kernel(vcpu->kcm) == (vcpu->arch.apic != NULL);
+}
+
 int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
 {
        struct kvm_vcpu *v;

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 03a1fd47a6d3b91a625d44f60d6c327b9fc5c9fe..9477dc6cccaed51790eee82bd1f8de9f2cbf70cc 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3199,6 +3199,9 @@ long kvm_arch_vm_ioctl(struct file *filp,
                r = -EEXIST;
                if (kvm->arch.vpic)
                        goto create_irqchip_unlock;
+               r = -EINVAL;
+               if (atomic_read(&kvm->online_vcpus))
+                       goto create_irqchip_unlock;
                r = -ENOMEM;
                vpic = kvm_create_pic(kvm);
                if (vpic) {
@@ -6107,6 +6110,11 @@ void kvm_arch_check_processor_compat(void *rtn)
        kvm_x86_ops->check_processor_compatibility(rtn);
 }
 
+bool kvm_vcpu_compatible(struct kvm_vcpu *vcpu)
+{
+       return irqchip_in_kernel(vcpu->kvm) == (vcpu->arch.apic != NULL);
+}
+
 int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
 {
        struct page *page;

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 355e44555c39c83026e83c70764417f425bd30a0..e42d85ae854101213827bccc44e73d1331d5426c 100644 (file)
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -805,6 +805,13 @@ static inline bool kvm_vcpu_is_bsp(struct kvm_vcpu *vcpu)
 {
        return vcpu->kvm->bsp_vcpu_id == vcpu->vcpu_id;
 }
+
+bool kvm_vcpu_compatible(struct kvm_vcpu *vcpu);
+
+#else
+
+static inline bool kvm_vcpu_compatible(struct kvm_vcpu *vcpu) { return true; }
+
 #endif
 
 #ifdef __KVM_HAVE_DEVICE_ASSIGNMENT

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e4431ada5947a81dcf60d8e36bb54a8847e2783d..94e148e38719af20bf67c96cf0da66d2374729db 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1651,6 +1651,10 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id)
                goto vcpu_destroy;
 
        mutex_lock(&kvm->lock);
+       if (!kvm_vcpu_compatible(vcpu)) {
+               r = -EINVAL;
+               goto unlock_vcpu_destroy;
+       }
        if (atomic_read(&kvm->online_vcpus) == KVM_MAX_VCPUS) {
                r = -EINVAL;
                goto unlock_vcpu_destroy;