diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index f4183c4c1ec8..ebea4fa69976 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -69,12 +69,15 @@ DEFINE_COOKIE(net_cookie);
 
 static struct net_generic *net_alloc_generic(void)
 {
+	unsigned int gen_ptrs = READ_ONCE(max_gen_ptrs);
+	unsigned int generic_size;
 	struct net_generic *ng;
-	unsigned int generic_size = offsetof(struct net_generic, ptr[max_gen_ptrs]);
+
+	generic_size = offsetof(struct net_generic, ptr[gen_ptrs]);
 
 	ng = kzalloc(generic_size, GFP_KERNEL);
 	if (ng)
-		ng->s.len = max_gen_ptrs;
+		ng->s.len = gen_ptrs;
 
 	return ng;
 }
@@ -1229,7 +1232,11 @@ static int register_pernet_operations(struct list_head *list,
 		if (error < 0)
 			return error;
 		*ops->id = error;
-		max_gen_ptrs = max(max_gen_ptrs, *ops->id + 1);
+		/* This does not require READ_ONCE as writers already hold
+		 * pernet_ops_rwsem. But WRITE_ONCE is needed to protect
+		 * net_alloc_generic.
+		 */
+		WRITE_ONCE(max_gen_ptrs, max(max_gen_ptrs, *ops->id + 1));
 	}
 	error = __register_pernet_operations(list, ops);
 	if (error) {