void ion_pages_sync_for_device(struct device *dev, struct page *page,
		size_t size, enum dma_data_direction dir)
{
	struct scatterlist sg;

	sg_init_table(&sg, 1);
	sg_set_page(&sg, page, size, 0);
	/*
	 * This is not correct - sg_dma_address needs a dma_addr_t that is valid
	 * for the targeted device, but this works on the currently targeted
	 * hardware.
	 */
	sg_dma_address(&sg) = page_to_phys(page);
	dma_sync_sg_for_device(dev, &sg, 1, dir);
}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.