void ion_device_add_heap(struct ion_device *dev, struct ion_heap *heap)
{
	struct dentry *debug_file;

	if (!heap->ops->allocate || !heap->ops->free || !heap->ops->map_dma ||
	    !heap->ops->unmap_dma)
		pr_err("%s: can not add heap with invalid ops struct.\n",
		       __func__);

	spin_lock_init(&heap->free_lock);
	heap->free_list_size = 0;

	if (heap->flags & ION_HEAP_FLAG_DEFER_FREE)
		ion_heap_init_deferred_free(heap);

	if ((heap->flags & ION_HEAP_FLAG_DEFER_FREE) || heap->ops->shrink)
		ion_heap_init_shrinker(heap);

	heap->dev = dev;
	down_write(&dev->lock);
	/*
	 * use negative heap->id to reverse the priority -- when traversing
	 * the list later attempt higher id numbers first
	 */
	plist_node_init(&heap->node, -heap->id);
	plist_add(&heap->node, &dev->heaps);
	debug_file = debugfs_create_file(heap->name, 0664,
					dev->heaps_debug_root, heap,
					&debug_heap_fops);

	if (!debug_file) {
		char buf[256], *path;

		path = dentry_path(dev->heaps_debug_root, buf, 256);
		pr_err("Failed to create heap debugfs at %s/%s\n",
			path, heap->name);
	}

	if (heap->shrinker.count_objects && heap->shrinker.scan_objects) {
		char debug_name[64];

		snprintf(debug_name, 64, "%s_shrink", heap->name);
		debug_file = debugfs_create_file(
			debug_name, 0644, dev->heaps_debug_root, heap,
			&debug_shrink_fops);
		if (!debug_file) {
			char buf[256], *path;

			path = dentry_path(dev->heaps_debug_root, buf, 256);
			pr_err("Failed to create heap shrinker debugfs at %s/%s\n",
				path, debug_name);
		}
	}

	up_write(&dev->lock);
}

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.