[PATCH net v1] net: qrtr: replace qrtr_tx_flow radix_tree with xarray to fix memory leak

[Jiayuan Chen <jiayuan.chen@linux.dev>]

From: Jiayuan Chen <jiayuan.chen@shopee.com>

__radix_tree_create() allocates and links intermediate nodes into the
tree one by one. If a subsequent allocation fails, the already-linked
nodes remain in the tree with no corresponding leaf entry. These orphaned
internal nodes are never reclaimed because radix_tree_for_each_slot()
only visits slots containing leaf values.

The radix_tree API is deprecated in favor of xarray. As suggested by
Matthew Wilcox, migrate qrtr_tx_flow from radix_tree to xarray instead
of fixing the radix_tree itself [1]. xarray properly handles cleanup of
internal nodes — xa_destroy() frees all internal xarray nodes when the
qrtr_node is released, preventing the leak.

[1] https://lore.kernel.org/all/20260225071623.41275-1-jiayuan.chen@linux.dev/T/
Reported-by: syzbot+006987d1be3586e13555@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/000000000000bfba3a060bf4ffcf@google.com/T/
Fixes: 5fdeb0d372ab ("net: qrtr: Implement outgoing flow control")
Cc: Jiayuan Chen <jiayuan.chen@linux.dev>
Signed-off-by: Jiayuan Chen <jiayuan.chen@shopee.com>
---
 net/qrtr/af_qrtr.c | 31 +++++++++++++------------------
 1 file changed, 13 insertions(+), 18 deletions(-)

diff --git a/net/qrtr/af_qrtr.c b/net/qrtr/af_qrtr.c
index 55fd2dd37588..d77e9c8212da 100644
--- a/net/qrtr/af_qrtr.c
+++ b/net/qrtr/af_qrtr.c
@@ -118,7 +118,7 @@ static DEFINE_XARRAY_ALLOC(qrtr_ports);
  * @ep: endpoint
  * @ref: reference count for node
  * @nid: node id
- * @qrtr_tx_flow: tree of qrtr_tx_flow, keyed by node << 32 | port
+ * @qrtr_tx_flow: xarray of qrtr_tx_flow, keyed by node << 32 | port
  * @qrtr_tx_lock: lock for qrtr_tx_flow inserts
  * @rx_queue: receive queue
  * @item: list item for broadcast list
@@ -129,7 +129,7 @@ struct qrtr_node {
 	struct kref ref;
 	unsigned int nid;
 
-	struct radix_tree_root qrtr_tx_flow;
+	struct xarray qrtr_tx_flow;
 	struct mutex qrtr_tx_lock; /* for qrtr_tx_flow */
 
 	struct sk_buff_head rx_queue;
@@ -172,6 +172,7 @@ static void __qrtr_node_release(struct kref *kref)
 	struct qrtr_tx_flow *flow;
 	unsigned long flags;
 	void __rcu **slot;
+	unsigned long index;
 
 	spin_lock_irqsave(&qrtr_nodes_lock, flags);
 	/* If the node is a bridge for other nodes, there are possibly
@@ -189,11 +190,9 @@ static void __qrtr_node_release(struct kref *kref)
 	skb_queue_purge(&node->rx_queue);
 
 	/* Free tx flow counters */
-	radix_tree_for_each_slot(slot, &node->qrtr_tx_flow, &iter, 0) {
-		flow = *slot;
-		radix_tree_iter_delete(&node->qrtr_tx_flow, &iter, slot);
+	xa_for_each(&node->qrtr_tx_flow, index, flow)
 		kfree(flow);
-	}
+	xa_destroy(&node->qrtr_tx_flow);
 	kfree(node);
 }
 
@@ -228,9 +227,7 @@ static void qrtr_tx_resume(struct qrtr_node *node, struct sk_buff *skb)
 
 	key = remote_node << 32 | remote_port;
 
-	rcu_read_lock();
-	flow = radix_tree_lookup(&node->qrtr_tx_flow, key);
-	rcu_read_unlock();
+	flow = xa_load(&node->qrtr_tx_flow, key);
 	if (flow) {
 		spin_lock(&flow->resume_tx.lock);
 		flow->pending = 0;
@@ -269,12 +266,13 @@ static int qrtr_tx_wait(struct qrtr_node *node, int dest_node, int dest_port,
 		return 0;
 
 	mutex_lock(&node->qrtr_tx_lock);
-	flow = radix_tree_lookup(&node->qrtr_tx_flow, key);
+	flow = xa_load(&node->qrtr_tx_flow, key);
 	if (!flow) {
 		flow = kzalloc_obj(*flow);
 		if (flow) {
 			init_waitqueue_head(&flow->resume_tx);
-			if (radix_tree_insert(&node->qrtr_tx_flow, key, flow)) {
+			if (xa_err(xa_store(&node->qrtr_tx_flow, key, flow,
+					    GFP_KERNEL))) {
 				kfree(flow);
 				flow = NULL;
 			}
@@ -326,9 +324,7 @@ static void qrtr_tx_flow_failed(struct qrtr_node *node, int dest_node,
 	unsigned long key = (u64)dest_node << 32 | dest_port;
 	struct qrtr_tx_flow *flow;
 
-	rcu_read_lock();
-	flow = radix_tree_lookup(&node->qrtr_tx_flow, key);
-	rcu_read_unlock();
+	flow = xa_load(&node->qrtr_tx_flow, key);
 	if (flow) {
 		spin_lock_irq(&flow->resume_tx.lock);
 		flow->tx_failed = 1;
@@ -599,7 +595,7 @@ int qrtr_endpoint_register(struct qrtr_endpoint *ep, unsigned int nid)
 	node->nid = QRTR_EP_NID_AUTO;
 	node->ep = ep;
 
-	INIT_RADIX_TREE(&node->qrtr_tx_flow, GFP_KERNEL);
+	xa_init(&node->qrtr_tx_flow);
 	mutex_init(&node->qrtr_tx_lock);
 
 	qrtr_node_assign(node, nid);
@@ -627,6 +623,7 @@ void qrtr_endpoint_unregister(struct qrtr_endpoint *ep)
 	struct qrtr_tx_flow *flow;
 	struct sk_buff *skb;
 	unsigned long flags;
+	unsigned long index;
 	void __rcu **slot;
 
 	mutex_lock(&node->ep_lock);
@@ -649,10 +646,8 @@ void qrtr_endpoint_unregister(struct qrtr_endpoint *ep)
 
 	/* Wake up any transmitters waiting for resume-tx from the node */
 	mutex_lock(&node->qrtr_tx_lock);
-	radix_tree_for_each_slot(slot, &node->qrtr_tx_flow, &iter, 0) {
-		flow = *slot;
+	xa_for_each(&node->qrtr_tx_flow, index, flow)
 		wake_up_interruptible_all(&flow->resume_tx);
-	}
 	mutex_unlock(&node->qrtr_tx_lock);
 
 	qrtr_node_release(node);
-- 
2.43.0