net: qrtr: ns: Change nodes radix tree to xarray

There is a use after free scenario while iterating through the nodes
radix tree despite the ns being a single threaded process. This can
happen when the radix tree APIs are not synchronized with the
rcu_read_lock() APIs.

Convert the radix tree for nodes to xarray to take advantage of the
built in rcu lock usage provided by xarray.
Signed-off-by: Chris Lew <quic_clew@quicinc.com>
Signed-off-by: Vignesh Viswanathan <quic_viswanat@quicinc.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/qrtr/ns.c

@@ -16,7 +16,7 @@
 #define CREATE_TRACE_POINTS
 #include <trace/events/qrtr.h>
 
-static RADIX_TREE(nodes, GFP_KERNEL);
+static DEFINE_XARRAY(nodes);
 
 static struct {
 	struct socket *sock;
@@ -73,7 +73,7 @@ static struct qrtr_node *node_get(unsigned int node_id)
 {
 	struct qrtr_node *node;
 
-	node = radix_tree_lookup(&nodes, node_id);
+	node = xa_load(&nodes, node_id);
 	if (node)
 		return node;
 
@@ -85,7 +85,7 @@ static struct qrtr_node *node_get(unsigned int node_id)
 	node->id = node_id;
 	xa_init(&node->servers);
 
-	if (radix_tree_insert(&nodes, node_id, node)) {
+	if (xa_store(&nodes, node_id, node, GFP_KERNEL)) {
 		kfree(node);
 		return NULL;
 	}