[PATCH 1/1] [CVE-2012-1601] [LUCID] KVM: Ensure all vcpus are consistent with in-kernel irqchip settings
Brad Figg
brad.figg at canonical.com
Thu Apr 26 16:37:39 UTC 2012
From: Avi Kivity <avi at redhat.com>
CVE-2012-1601
BugLink: http://bugs.launchpad.net/bugs/971685
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 at ellerman.id.au>
Signed-off-by: Avi Kivity <avi at redhat.com>
(backported from commit 3e515705a1f46beb1c942bb8043c16f8ac7b1e9e upstream)
Signed-off-by: Brad Figg <brad.figg at canonical.com>
---
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(+)
diff --git a/arch/ia64/kvm/kvm-ia64.c b/arch/ia64/kvm/kvm-ia64.c
index 2eb6365..416122b 100644
--- a/arch/ia64/kvm/kvm-ia64.c
+++ b/arch/ia64/kvm/kvm-ia64.c
@@ -1185,6 +1185,11 @@ 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 7000a5e..34813ce 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2274,6 +2274,9 @@ long kvm_arch_vm_ioctl(struct file *filp,
goto out;
break;
case KVM_CREATE_IRQCHIP:
+ r = -EINVAL;
+ if (atomic_read(&kvm->online_vcpus))
+ goto out;
r = -ENOMEM;
kvm->arch.vpic = kvm_create_pic(kvm);
if (kvm->arch.vpic) {
@@ -5007,6 +5010,11 @@ 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 1296deb..624cf6b 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -557,5 +557,12 @@ 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
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 42d7353..a27f14f 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1872,6 +1872,10 @@ 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;
--
1.7.9.5
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