KVM: Fix possible circular locking in kvm_vm_ioctl_assign_device()

Commit Message

Sheng Yang Dec. 15, 2009, 2:28 a.m. UTC

None

Patch

diff --git a/virt/kvm/assigned-dev.c b/virt/kvm/assigned-dev.c
index fd9c097..f73de63 100644
--- a/virt/kvm/assigned-dev.c
+++ b/virt/kvm/assigned-dev.c
@@ -508,8 +508,8 @@  static int kvm_vm_ioctl_assign_device(struct kvm *kvm,
 	struct kvm_assigned_dev_kernel *match;
 	struct pci_dev *dev;
 
-	down_read(&kvm->slots_lock);
 	mutex_lock(&kvm->lock);
+	down_read(&kvm->slots_lock);
 
 	match = kvm_find_assigned_dev(&kvm->arch.assigned_dev_head,
 				      assigned_dev->assigned_dev_id);
@@ -573,8 +573,8 @@  static int kvm_vm_ioctl_assign_device(struct kvm *kvm,
 	}
 
 out:
-	mutex_unlock(&kvm->lock);
 	up_read(&kvm->slots_lock);
+	mutex_unlock(&kvm->lock);
 	return r;
 out_list_del:
 	list_del(&match->list);
@@ -585,8 +585,8 @@  out_put:
 	pci_dev_put(dev);
 out_free:
 	kfree(match);
-	mutex_unlock(&kvm->lock);
 	up_read(&kvm->slots_lock);
+	mutex_unlock(&kvm->lock);
 	return r;
 }
 
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index f92ba13..91b84c9 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -63,7 +63,7 @@  MODULE_LICENSE("GPL");
 /*
  * Ordering of locks:
  *
- * 		kvm->slots_lock --> kvm->lock --> kvm->irq_lock
+ * 		kvm->lock --> kvm->slots_lock --> kvm->irq_lock
  */
 
 DEFINE_SPINLOCK(kvm_lock);