static void vfio_pci_probe_mmaps(struct vfio_pci_device *vdev)
{
	struct resource *res;
	int bar;
	struct vfio_pci_dummy_resource *dummy_res;

	INIT_LIST_HEAD(&vdev->dummy_resources_list);

	for (bar = PCI_STD_RESOURCES; bar <= PCI_STD_RESOURCE_END; bar++) {
		res = vdev->pdev->resource + bar;

		if (!IS_ENABLED(CONFIG_VFIO_PCI_MMAP))
			goto no_mmap;

		if (!(res->flags & IORESOURCE_MEM))
			goto no_mmap;

		/*
		 * The PCI core shouldn't set up a resource with a
		 * type but zero size. But there may be bugs that
		 * cause us to do that.
		 */
		if (!resource_size(res))
			goto no_mmap;

		if (resource_size(res) >= PAGE_SIZE) {
			vdev->bar_mmap_supported[bar] = true;
			continue;
		}

		if (!(res->start & ~PAGE_MASK)) {
			/*
			 * Add a dummy resource to reserve the remainder
			 * of the exclusive page in case that hot-add
			 * device's bar is assigned into it.
			 */
			dummy_res = kzalloc(sizeof(*dummy_res), GFP_KERNEL);
			if (dummy_res == NULL)
				goto no_mmap;

			dummy_res->resource.name = "vfio sub-page reserved";
			dummy_res->resource.start = res->end + 1;
			dummy_res->resource.end = res->start + PAGE_SIZE - 1;
			dummy_res->resource.flags = res->flags;
			if (request_resource(res->parent,
						&dummy_res->resource)) {
				kfree(dummy_res);
				goto no_mmap;
			}
			dummy_res->index = bar;
			list_add(&dummy_res->res_next,
					&vdev->dummy_resources_list);
			vdev->bar_mmap_supported[bar] = true;
			continue;
		}
		/*
		 * Here we don't handle the case when the BAR is not page
		 * aligned because we can't expect the BAR will be
		 * assigned into the same location in a page in guest
		 * when we passthrough the BAR. And it's hard to access
		 * this BAR in userspace because we have no way to get
		 * the BAR's location in a page.
		 */
no_mmap:
		vdev->bar_mmap_supported[bar] = false;
	}
}

The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.