iommufd: Add iopt_area_alloc()

We never initialize the two interval tree nodes, and zero fill is not the
same as RB_CLEAR_NODE. This can hide issues where we missed adding the
area to the trees. Factor out the allocation and clear the two nodes.

Fixes: 51fe614 ("iommufd: Data structure to provide IOVA to PFN mapping")
Link: https://lore.kernel.org/r/20231030145035.GG691768@ziepe.ca
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

Author: jgunthorpe

drivers/iommu/iommufd/io_pagetable.c

@@ -222,6 +222,18 @@ static int iopt_insert_area(struct io_pagetable *iopt, struct iopt_area *area,
 	return 0;
 }
 
+static struct iopt_area *iopt_area_alloc(void)
+{
+	struct iopt_area *area;
+
+	area = kzalloc(sizeof(*area), GFP_KERNEL_ACCOUNT);
+	if (!area)
+		return NULL;
+	RB_CLEAR_NODE(&area->node.rb);
+	RB_CLEAR_NODE(&area->pages_node.rb);
+	return area;
+}
+
 static int iopt_alloc_area_pages(struct io_pagetable *iopt,
 				 struct list_head *pages_list,
 				 unsigned long length, unsigned long *dst_iova,
@@ -232,7 +244,7 @@ static int iopt_alloc_area_pages(struct io_pagetable *iopt,
 	int rc = 0;
 
 	list_for_each_entry(elm, pages_list, next) {
-		elm->area = kzalloc(sizeof(*elm->area), GFP_KERNEL_ACCOUNT);
+		elm->area = iopt_area_alloc();
 		if (!elm->area)
 			return -ENOMEM;
 	}
@@ -1177,11 +1189,11 @@ static int iopt_area_split(struct iopt_area *area, unsigned long iova)
 	    iopt_area_start_byte(area, new_start) & (alignment - 1))
 		return -EINVAL;
 
-	lhs = kzalloc(sizeof(*area), GFP_KERNEL_ACCOUNT);
+	lhs = iopt_area_alloc();
 	if (!lhs)
 		return -ENOMEM;
 
-	rhs = kzalloc(sizeof(*area), GFP_KERNEL_ACCOUNT);
+	rhs = iopt_area_alloc();
 	if (!rhs) {
 		rc = -ENOMEM;
 		goto err_free_lhs;

drivers/iommu/iommufd/pages.c

@@ -1507,6 +1507,8 @@ void iopt_area_unfill_domains(struct iopt_area *area, struct iopt_pages *pages)
 				area, domain, iopt_area_index(area),
 				iopt_area_last_index(area));
 
+	if (IS_ENABLED(CONFIG_IOMMUFD_TEST))
+		WARN_ON(RB_EMPTY_NODE(&area->pages_node.rb));
 	interval_tree_remove(&area->pages_node, &pages->domains_itree);
 	iopt_area_unfill_domain(area, pages, area->storage_domain);
 	area->storage_domain = NULL;