static int ion_handle_add(struct ion_client *client, struct ion_handle *handle)
{
	int id;
	struct rb_node **p = &client->handles.rb_node;
	struct rb_node *parent = NULL;
	struct ion_handle *entry;

	id = idr_alloc(&client->idr, handle, 1, 0, GFP_KERNEL);
	if (id < 0)
		return id;

	handle->id = id;

	while (*p) {
		parent = *p;
		entry = rb_entry(parent, struct ion_handle, node);

		if (handle->buffer < entry->buffer)
			p = &(*p)->rb_left;
		else if (handle->buffer > entry->buffer)
			p = &(*p)->rb_right;
		else
			WARN(1, "%s: buffer already found.", __func__);
	}

	rb_link_node(&handle->node, parent, p);
	rb_insert_color(&handle->node, &client->handles);

	return 0;
}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.