Patchwork [4/4] KVM: Ensure all vcpus are consistent with in-kernel irqchip settings

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Submitter Herton Ronaldo Krzesinski
Date June 29, 2012, 4:32 p.m.
Message ID <1340987524-22261-5-git-send-email-herton.krzesinski@canonical.com>
Download mbox | patch
Permalink /patch/168179/
State New
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Comments

Herton Ronaldo Krzesinski - June 29, 2012, 4:32 p.m.
From: Avi Kivity <avi@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@ellerman.id.au>
Signed-off-by: Avi Kivity <avi@redhat.com>
(backported from commit 3e515705a1f46beb1c942bb8043c16f8ac7b1e9e upstream)
Signed-off-by: Brad Figg <brad.figg@canonical.com>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
---
 arch/x86/kvm/x86.c                                 |    9 +++++++++
 .../binary-custom.d/openvz/src/arch/x86/kvm/x86.c  |    9 +++++++++
 .../openvz/src/include/linux/kvm_host.h            |    2 ++
 .../binary-custom.d/openvz/src/virt/kvm/kvm_main.c |    5 +++++
 debian/binary-custom.d/xen/src/arch/x86/kvm/x86.c  |    9 +++++++++
 .../xen/src/include/linux/kvm_host.h               |    2 ++
 debian/binary-custom.d/xen/src/virt/kvm/kvm_main.c |    5 +++++
 include/linux/kvm_host.h                           |    2 ++
 virt/kvm/kvm_main.c                                |    5 +++++
 9 files changed, 48 insertions(+)

Patch

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9331b67..d6d7cfe 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1582,6 +1582,9 @@  long kvm_arch_vm_ioctl(struct file *filp,
 		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) {
@@ -3350,6 +3353,11 @@  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;
@@ -3435,6 +3443,7 @@  static void kvm_free_vcpus(struct kvm *kvm)
 		}
 	}
 
+	atomic_set(&kvm->online_vcpus, 0);
 }
 
 void kvm_arch_destroy_vm(struct kvm *kvm)
diff --git a/debian/binary-custom.d/openvz/src/arch/x86/kvm/x86.c b/debian/binary-custom.d/openvz/src/arch/x86/kvm/x86.c
index 9331b67..d6d7cfe 100644
--- a/debian/binary-custom.d/openvz/src/arch/x86/kvm/x86.c
+++ b/debian/binary-custom.d/openvz/src/arch/x86/kvm/x86.c
@@ -1582,6 +1582,9 @@  long kvm_arch_vm_ioctl(struct file *filp,
 		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) {
@@ -3350,6 +3353,11 @@  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;
@@ -3435,6 +3443,7 @@  static void kvm_free_vcpus(struct kvm *kvm)
 		}
 	}
 
+	atomic_set(&kvm->online_vcpus, 0);
 }
 
 void kvm_arch_destroy_vm(struct kvm *kvm)
diff --git a/debian/binary-custom.d/openvz/src/include/linux/kvm_host.h b/debian/binary-custom.d/openvz/src/include/linux/kvm_host.h
index 588e4f9..95ec906 100644
--- a/debian/binary-custom.d/openvz/src/include/linux/kvm_host.h
+++ b/debian/binary-custom.d/openvz/src/include/linux/kvm_host.h
@@ -121,6 +121,7 @@  struct kvm {
 	struct kvm_memory_slot memslots[KVM_MEMORY_SLOTS +
 					KVM_PRIVATE_MEM_SLOTS];
 	struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
+	atomic_t online_vcpus;
 	struct list_head vm_list;
 	struct file *filp;
 	struct kvm_io_bus mmio_bus;
@@ -307,5 +308,6 @@  struct kvm_stats_debugfs_item {
 	struct dentry *dentry;
 };
 extern struct kvm_stats_debugfs_item debugfs_entries[];
+bool kvm_vcpu_compatible(struct kvm_vcpu *vcpu);
 
 #endif
diff --git a/debian/binary-custom.d/openvz/src/virt/kvm/kvm_main.c b/debian/binary-custom.d/openvz/src/virt/kvm/kvm_main.c
index 07adef4..d9a8ae0 100644
--- a/debian/binary-custom.d/openvz/src/virt/kvm/kvm_main.c
+++ b/debian/binary-custom.d/openvz/src/virt/kvm/kvm_main.c
@@ -802,11 +802,16 @@  static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, int n)
 		return r;
 
 	mutex_lock(&kvm->lock);
+	if (!kvm_vcpu_compatible(vcpu)) {
+		r = -EINVAL;
+		goto vcpu_destroy;
+	}
 	if (kvm->vcpus[n]) {
 		r = -EEXIST;
 		goto vcpu_destroy;
 	}
 	kvm->vcpus[n] = vcpu;
+	atomic_inc(&kvm->online_vcpus);
 	mutex_unlock(&kvm->lock);
 
 	/* Now it's all set up, let userspace reach it */
diff --git a/debian/binary-custom.d/xen/src/arch/x86/kvm/x86.c b/debian/binary-custom.d/xen/src/arch/x86/kvm/x86.c
index 9331b67..d6d7cfe 100644
--- a/debian/binary-custom.d/xen/src/arch/x86/kvm/x86.c
+++ b/debian/binary-custom.d/xen/src/arch/x86/kvm/x86.c
@@ -1582,6 +1582,9 @@  long kvm_arch_vm_ioctl(struct file *filp,
 		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) {
@@ -3350,6 +3353,11 @@  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;
@@ -3435,6 +3443,7 @@  static void kvm_free_vcpus(struct kvm *kvm)
 		}
 	}
 
+	atomic_set(&kvm->online_vcpus, 0);
 }
 
 void kvm_arch_destroy_vm(struct kvm *kvm)
diff --git a/debian/binary-custom.d/xen/src/include/linux/kvm_host.h b/debian/binary-custom.d/xen/src/include/linux/kvm_host.h
index 588e4f9..95ec906 100644
--- a/debian/binary-custom.d/xen/src/include/linux/kvm_host.h
+++ b/debian/binary-custom.d/xen/src/include/linux/kvm_host.h
@@ -121,6 +121,7 @@  struct kvm {
 	struct kvm_memory_slot memslots[KVM_MEMORY_SLOTS +
 					KVM_PRIVATE_MEM_SLOTS];
 	struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
+	atomic_t online_vcpus;
 	struct list_head vm_list;
 	struct file *filp;
 	struct kvm_io_bus mmio_bus;
@@ -307,5 +308,6 @@  struct kvm_stats_debugfs_item {
 	struct dentry *dentry;
 };
 extern struct kvm_stats_debugfs_item debugfs_entries[];
+bool kvm_vcpu_compatible(struct kvm_vcpu *vcpu);
 
 #endif
diff --git a/debian/binary-custom.d/xen/src/virt/kvm/kvm_main.c b/debian/binary-custom.d/xen/src/virt/kvm/kvm_main.c
index 07adef4..d9a8ae0 100644
--- a/debian/binary-custom.d/xen/src/virt/kvm/kvm_main.c
+++ b/debian/binary-custom.d/xen/src/virt/kvm/kvm_main.c
@@ -802,11 +802,16 @@  static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, int n)
 		return r;
 
 	mutex_lock(&kvm->lock);
+	if (!kvm_vcpu_compatible(vcpu)) {
+		r = -EINVAL;
+		goto vcpu_destroy;
+	}
 	if (kvm->vcpus[n]) {
 		r = -EEXIST;
 		goto vcpu_destroy;
 	}
 	kvm->vcpus[n] = vcpu;
+	atomic_inc(&kvm->online_vcpus);
 	mutex_unlock(&kvm->lock);
 
 	/* Now it's all set up, let userspace reach it */
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 588e4f9..95ec906 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -121,6 +121,7 @@  struct kvm {
 	struct kvm_memory_slot memslots[KVM_MEMORY_SLOTS +
 					KVM_PRIVATE_MEM_SLOTS];
 	struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
+	atomic_t online_vcpus;
 	struct list_head vm_list;
 	struct file *filp;
 	struct kvm_io_bus mmio_bus;
@@ -307,5 +308,6 @@  struct kvm_stats_debugfs_item {
 	struct dentry *dentry;
 };
 extern struct kvm_stats_debugfs_item debugfs_entries[];
+bool kvm_vcpu_compatible(struct kvm_vcpu *vcpu);
 
 #endif
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 07adef4..d9a8ae0 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -802,11 +802,16 @@  static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, int n)
 		return r;
 
 	mutex_lock(&kvm->lock);
+	if (!kvm_vcpu_compatible(vcpu)) {
+		r = -EINVAL;
+		goto vcpu_destroy;
+	}
 	if (kvm->vcpus[n]) {
 		r = -EEXIST;
 		goto vcpu_destroy;
 	}
 	kvm->vcpus[n] = vcpu;
+	atomic_inc(&kvm->online_vcpus);
 	mutex_unlock(&kvm->lock);
 
 	/* Now it's all set up, let userspace reach it */