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Commit fae3a353 authored by Sheng Yang's avatar Sheng Yang Committed by Marcelo Tosatti
Browse files

KVM: Fix possible circular locking in kvm_vm_ioctl_assign_device() 



One possible order is:

KVM_CREATE_IRQCHIP ioctl(took kvm->lock) -> kvm_iobus_register_dev() ->
down_write(kvm->slots_lock).

The other one is in kvm_vm_ioctl_assign_device(), which take kvm->slots_lock
first, then kvm->lock.

Update the comment of lock order as well.

Observe it due to kernel locking debug warnings.

Cc: stable@kernel.org
Signed-off-by: default avatarSheng Yang <sheng@linux.intel.com>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent fb341f57

virt/kvm/assigned-dev.c

+3 −3
Original line number Diff line number Diff line
@@ -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 @@ static int kvm_vm_ioctl_assign_device(struct kvm *kvm, 
	pci_dev_put(dev);

out_free:

	kfree(match);

	mutex_unlock(&kvm->lock);

	up_read(&kvm->slots_lock);

	mutex_unlock(&kvm->lock);

	return r;

}

virt/kvm/kvm_main.c

+1 −1
Original line number Diff line number Diff line
@@ -64,7 +64,7 @@ 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);