1 files changed, 22 insertions, 6 deletions

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index d69ebba81beb..de91dd88705b 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -306,13 +306,23 @@ static int __iommu_probe_device(struct device *dev, struct list_head *group_list
 	const struct iommu_ops *ops = dev->bus->iommu_ops;
 	struct iommu_device *iommu_dev;
 	struct iommu_group *group;
+	static DEFINE_MUTEX(iommu_probe_device_lock);
 	int ret;
 
 	if (!ops)
 		return -ENODEV;
-
-	if (!dev_iommu_get(dev))
-		return -ENOMEM;
+	/*
+	 * Serialise to avoid races between IOMMU drivers registering in
+	 * parallel and/or the "replay" calls from ACPI/OF code via client
+	 * driver probe. Once the latter have been cleaned up we should
+	 * probably be able to use device_lock() here to minimise the scope,
+	 * but for now enforcing a simple global ordering is fine.
+	 */
+	mutex_lock(&iommu_probe_device_lock);
+	if (!dev_iommu_get(dev)) {
+		ret = -ENOMEM;
+		goto err_unlock;
+	}
 
 	if (!try_module_get(ops->owner)) {
 		ret = -EINVAL;
@@ -333,11 +343,14 @@ static int __iommu_probe_device(struct device *dev, struct list_head *group_list
 		ret = PTR_ERR(group);
 		goto out_release;
 	}
-	iommu_group_put(group);
 
+	mutex_lock(&group->mutex);
 	if (group_list && !group->default_domain && list_empty(&group->entry))
 		list_add_tail(&group->entry, group_list);
+	mutex_unlock(&group->mutex);
+	iommu_group_put(group);
 
+	mutex_unlock(&iommu_probe_device_lock);
 	iommu_device_link(iommu_dev, dev);
 
 	return 0;
@@ -352,6 +365,9 @@ out_module_put:
 err_free:
 	dev_iommu_free(dev);
 
+err_unlock:
+	mutex_unlock(&iommu_probe_device_lock);
+
 	return ret;
 }
 
@@ -1824,11 +1840,11 @@ int bus_iommu_probe(struct bus_type *bus)
 		return ret;
 
 	list_for_each_entry_safe(group, next, &group_list, entry) {
+		mutex_lock(&group->mutex);
+
 		/* Remove item from the list */
 		list_del_init(&group->entry);
 
-		mutex_lock(&group->mutex);
-
 		/* Try to allocate default domain */
 		probe_alloc_default_domain(bus, group);