iommufd: Fix missing update of domains_itree after splitting iopt_area

In iopt_area_split(), if the original iopt_area has filled a domain and is
linked to domains_itree, pages_nodes have to be properly
reinserted. Otherwise the domains_itree becomes corrupted and we will UAF.

Fixes: 51fe6141 ("iommufd: Data structure to provide IOVA to PFN mapping")
Link: https://lore.kernel.org/r/20231027162941.2864615-2-den@valinux.co.jp
Cc: stable@vger.kernel.org
Signed-off-by: Koichiro Den <den@valinux.co.jp>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/iommu/iommufd/io_pagetable.c

@@ -1220,6 +1220,16 @@ static int iopt_area_split(struct iopt_area *area, unsigned long iova)
 	if (WARN_ON(rc))
 		goto err_remove_lhs;
 
+	/*
+	 * If the original area has filled a domain, domains_itree has to be
+	 * updated.
+	 */
+	if (area->storage_domain) {
+		interval_tree_remove(&area->pages_node, &pages->domains_itree);
+		interval_tree_insert(&lhs->pages_node, &pages->domains_itree);
+		interval_tree_insert(&rhs->pages_node, &pages->domains_itree);
+	}
+
 	lhs->storage_domain = area->storage_domain;
 	lhs->pages = area->pages;
 	rhs->storage_domain = area->storage_domain;