Re: [syzbot] [arm-msm?] [net?] memory leak in radix_tree_insert

[syzbot <syzbot+006987d1be3586e13555@syzkaller.appspotmail.com>]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org.

***

Subject: [arm-msm?] [net?] memory leak in radix_tree_insert
Author: lizhi.xu@windriver.com

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 33cc938e65a9

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index a89df8afa510..0a2dfecdcd30 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -613,12 +613,13 @@ static int __radix_tree_create(struct radix_tree_root *root,
 		unsigned long index, struct radix_tree_node **nodep,
 		void __rcu ***slotp)
 {
-	struct radix_tree_node *node = NULL, *child;
+	struct radix_tree_node *node = NULL, *child, *orig;
 	void __rcu **slot = (void __rcu **)&root->xa_head;
 	unsigned long maxindex;
-	unsigned int shift, offset = 0;
+	unsigned int shift, offset = 0, mmshift = 0;
 	unsigned long max = index;
 	gfp_t gfp = root_gfp_mask(root);
+	int ret;
 
 	shift = radix_tree_load_root(root, &child, &maxindex);
 
@@ -628,7 +629,9 @@ static int __radix_tree_create(struct radix_tree_root *root,
 		if (error < 0)
 			return error;
 		shift = error;
+		mmshift = error;
 		child = rcu_dereference_raw(root->xa_head);
+		orig = child;
 	}
 
 	while (shift > 0) {
@@ -637,8 +640,11 @@ static int __radix_tree_create(struct radix_tree_root *root,
 			/* Have to add a child node.  */
 			child = radix_tree_node_alloc(gfp, node, root, shift,
 							offset, 0, 0);
-			if (!child)
-				return -ENOMEM;
+			printk("nc: %p\n", child);
+			if (!child) {
+				 ret = -ENOMEM;
+				 goto freec;
+			}
 			rcu_assign_pointer(*slot, node_to_entry(child));
 			if (node)
 				node->count++;
@@ -656,6 +662,18 @@ static int __radix_tree_create(struct radix_tree_root *root,
 	if (slotp)
 		*slotp = slot;
 	return 0;
+freec:
+	if (mmshift > 0) {
+		struct radix_tree_node *dn;
+		while (shift < mmshift) {
+			radix_tree_descend(orig, &dn, index);
+			printk("dc: %p\n", dn);
+			orig = orig->slots[0];
+			radix_tree_node_rcu_free(&dn->rcu_head);
+			shift += RADIX_TREE_MAP_SHIFT;
+		}
+	}
+	return ret;
 }
 
 /*