[ 27/56] KVM: Ensure all vcpus are consistent with in-kernel irqchip settings

Greg Kroah-Hartman
2013-04-02T22:57:32Z

From: Avi Kivity <avi@redhat.com>

commit 3e515705a1f46beb1c942bb8043c16f8ac7b1e9e upstream.

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>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/ia64/kvm/kvm-ia64.c | 5 +++++
arch/x86/kvm/x86.c | 8 ++++++++
include/linux/kvm_host.h | 7 +++++++
virt/kvm/kvm_main.c | 4 ++++
4 files changed, 24 insertions(+)

--- a/arch/ia64/kvm/kvm-ia64.c
+++ b/arch/ia64/kvm/kvm-ia64.c
@@ -1168,6 +1168,11 @@ 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;
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3410,6 +3410,9 @@ 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) {
@@ -6189,6 +6192,11 @@ void kvm_arch_check_processor_compat(voi
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;
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -736,6 +736,13 @@ static inline bool kvm_vcpu_is_bsp(struc
{
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
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1619,6 +1619,10 @@ static int kvm_vm_ioctl_create_vcpu(stru
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;