Subject: [PATCH net-next v2 14/14] netdevsim: release pinned PSP ext on drop paths

From: [email-masked]
Date: Sat, 14 Mar 2026 14:13:48 -0600

From: Wesley Atwell <[email-masked]>

nsim_do_psp() can leave an extra extension reference pinned until
nsim_psp_handle_ext() reattaches it to a forwarded skb.

Route the drop paths through a common helper and release that extra
reference when __dev_forward_skb() fails and when start_xmit() drops the
skb before it reaches the peer RX path.

This is separate from the peer RX truesize test hook itself.

Signed-off-by: Wesley Atwell <[email-masked]>
---
 drivers/net/netdevsim/netdev.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/drivers/net/netdevsim/netdev.c b/drivers/net/netdevsim/netdev.c
index 22238df79b6a..c22513c523d6 100644
--- a/drivers/net/netdevsim/netdev.c
+++ b/drivers/net/netdevsim/netdev.c
@@ -187,6 +187,15 @@ static int nsim_napi_rx(struct net_device *tx_dev, struct net_device *rx_dev,
 	return NET_RX_SUCCESS;
 }
 
+/* nsim_do_psp() pins an extra extension ref until nsim_psp_handle_ext()
+ * reattaches it to a forwarded skb.
+ */
+static void nsim_psp_ext_put(struct skb_ext *psp_ext)
+{
+	if (psp_ext)
+		__skb_ext_put(psp_ext);
+}
+
 static int nsim_forward_skb(struct net_device *tx_dev,
 			    struct net_device *rx_dev,
 			    struct sk_buff *skb,
@@ -196,8 +205,10 @@ static int nsim_forward_skb(struct net_device *tx_dev,
 	int ret;
 
 	ret = __dev_forward_skb(rx_dev, skb);
-	if (ret)
+	if (ret) {
+		nsim_psp_ext_put(psp_ext);
 		return ret;
+	}
 
 	nsim_psp_handle_ext(skb, psp_ext);
 
@@ -278,11 +289,8 @@ static netdev_tx_t nsim_start_xmit(struct sk_buff *skb, struct net_device *dev)
 		 * the synthetic cost; sender-side skb accounting stays put.
 		 */
 		nskb = skb_clone(skb, GFP_ATOMIC);
-		if (!nskb) {
-			if (psp_ext)
-				__skb_ext_put(psp_ext);
+		if (!nskb)
 			goto out_drop_free;
-		}
 
 		consume_skb(skb);
 		skb = nskb;
@@ -303,6 +311,7 @@ static netdev_tx_t nsim_start_xmit(struct sk_buff *skb, struct net_device *dev)
 out_drop_any:
 	dr = SKB_DROP_REASON_NOT_SPECIFIED;
 out_drop_free:
+	nsim_psp_ext_put(psp_ext);
 	kfree_skb_reason(skb, dr);
 out_drop_cnt:
 	rcu_read_unlock();
-- 
2.43.0