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

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commit 3e515705a1 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>
[dannf: backported to Debian's 2.6.32]
Signed-off-by: Willy Tarreau <w@1wt.eu>
This commit is contained in:
Avi Kivity 2012-03-05 14:23:29 +02:00 committed by Willy Tarreau
parent 49ef5906f1
commit ac802e6ad8
4 changed files with 24 additions and 0 deletions
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5
arch/ia64/kvm/kvm-ia64.c
View File

@ -1185,6 +1185,11 @@ static enum hrtimer_restart hlt_timer_fn(struct hrtimer *data)
#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;

8
arch/x86/kvm/x86.c
View File

@ -2280,6 +2280,9 @@ 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) {
@ -5027,6 +5030,11 @@ 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;

7
include/linux/kvm_host.h
View File

@ -556,5 +556,12 @@ 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
#endif

4
virt/kvm/kvm_main.c
View File

@ -1857,6 +1857,10 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id)
return r;
mutex_lock(&kvm->lock);
if (!kvm_vcpu_compatible(vcpu)) {
r = -EINVAL;
goto vcpu_destroy;
}
if (atomic_read(&kvm->online_vcpus) == KVM_MAX_VCPUS) {
r = -EINVAL;
goto vcpu_destroy;