iommu: Fix reference count leak in iommu_group_alloc.

BugLink: https://bugs.launchpad.net/bugs/1883917

[ Upstream commit 7cc31613 ]

kobject_init_and_add() takes reference even when it fails.
Thus, when kobject_init_and_add() returns an error,
kobject_put() must be called to properly clean up the kobject.

Fixes: d72e31c9 ("iommu: IOMMU Groups")
Signed-off-by: Qiushi Wu <wu000273@umn.edu>
Link: https://lore.kernel.org/r/20200527210020.6522-1-wu000273@umn.eduSigned-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

drivers/iommu/iommu.c

@@ -206,7 +206,7 @@ struct iommu_group *iommu_group_alloc(void)
 		mutex_lock(&iommu_group_mutex);
 		ida_remove(&iommu_group_ida, group->id);
 		mutex_unlock(&iommu_group_mutex);
-		kfree(group);
+		kobject_put(&group->kobj);
 		return ERR_PTR(ret);
 	}