iommu: Extend mutex lock scope in iommu_probe_device()

Extend the scope of holding group->mutex so that it can cover the default
domain check/attachment and direct mappings of reserved regions.

Cc: Ashish Mhetre <amhetre@nvidia.com>
Fixes: 211ff31 ("iommu: Fix race condition during default domain allocation")
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20211108061349.1985579-1-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

Author: LuBaolu

drivers/iommu/iommu.c

@@ -288,18 +288,19 @@ int iommu_probe_device(struct device *dev)
 	 */
 	mutex_lock(&group->mutex);
 	iommu_alloc_default_domain(group, dev);
-	mutex_unlock(&group->mutex);
 
 	if (group->default_domain) {
 		ret = __iommu_attach_device(group->default_domain, dev);
 		if (ret) {
+			mutex_unlock(&group->mutex);
 			iommu_group_put(group);
 			goto err_release;
 		}
 	}
 
 	iommu_create_device_direct_mappings(group, dev);
 
+	mutex_unlock(&group->mutex);
 	iommu_group_put(group);
 
 	if (ops->probe_finalize)