iommu: Fix refcount leak in iommu_device_claim_dma_owner

iommu_group_get() returns the group with the reference incremented.
Move iommu_group_get() after owner check to fix the refcount leak.

Fixes: 89395cc ("iommu: Add device-centric DMA ownership interfaces")
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20221230083100.1489569-1-linmq006@gmail.com
[ joro: Remove *group = NULL initialization ]
Signed-off-by: Joerg Roedel <jroedel@suse.de>

Author: Yuuoniy

drivers/iommu/iommu.c

@@ -3185,14 +3185,16 @@ EXPORT_SYMBOL_GPL(iommu_group_claim_dma_owner);
  */
 int iommu_device_claim_dma_owner(struct device *dev, void *owner)
 {
-	struct iommu_group *group = iommu_group_get(dev);
+	struct iommu_group *group;
 	int ret = 0;
 
-	if (!group)
-		return -ENODEV;
 	if (WARN_ON(!owner))
 		return -EINVAL;
 
+	group = iommu_group_get(dev);
+	if (!group)
+		return -ENODEV;
+
 	mutex_lock(&group->mutex);
 	if (group->owner_cnt) {
 		if (group->owner != owner) {