[PATCH net v4 2/2] net: hsr: fix VLAN add unwind on slave errors

[luka.gejak@linux.dev]

From: Luka Gejak <luka.gejak@linux.dev>

When vlan_vid_add() fails for a secondary slave, the error path calls
vlan_vid_del() on the failing port instead of the peer slave that had
already succeeded. This results in asymmetric VLAN state across the HSR
pair.

Fix this by switching to a centralized unwind path that removes the VID
from any slave device that was already programmed.

Fixes: 1a8a63a5305e ("net: hsr: Add VLAN CTAG filter support")
Signed-off-by: Luka Gejak <luka.gejak@linux.dev>
---
 net/hsr/hsr_device.c | 32 +++++++++++++++++---------------
 1 file changed, 17 insertions(+), 15 deletions(-)

diff --git a/net/hsr/hsr_device.c b/net/hsr/hsr_device.c
index 90236028817d..5555b71ab19b 100644
--- a/net/hsr/hsr_device.c
+++ b/net/hsr/hsr_device.c
@@ -532,8 +532,8 @@ static void hsr_change_rx_flags(struct net_device *dev, int change)
 static int hsr_ndo_vlan_rx_add_vid(struct net_device *dev,
 				   __be16 proto, u16 vid)
 {
-	bool is_slave_a_added = false;
-	bool is_slave_b_added = false;
+	struct net_device *slave_a_dev = NULL;
+	struct net_device *slave_b_dev = NULL;
 	struct hsr_port *port;
 	struct hsr_priv *hsr;
 	int ret = 0;
@@ -549,33 +549,35 @@ static int hsr_ndo_vlan_rx_add_vid(struct net_device *dev,
 		switch (port->type) {
 		case HSR_PT_SLAVE_A:
 			if (ret) {
-				/* clean up Slave-B */
 				netdev_err(dev, "add vid failed for Slave-A\n");
-				if (is_slave_b_added)
-					vlan_vid_del(port->dev, proto, vid);
-				return ret;
+				goto unwind;
 			}
-
-			is_slave_a_added = true;
+			slave_a_dev = port->dev;
 			break;
-
 		case HSR_PT_SLAVE_B:
 			if (ret) {
-				/* clean up Slave-A */
 				netdev_err(dev, "add vid failed for Slave-B\n");
-				if (is_slave_a_added)
-					vlan_vid_del(port->dev, proto, vid);
-				return ret;
+				goto unwind;
 			}
-
-			is_slave_b_added = true;
+			slave_b_dev = port->dev;
 			break;
 		default:
+			if (ret)
+				goto unwind;
 			break;
 		}
 	}
 
 	return 0;
+
+unwind:
+	if (slave_a_dev)
+		vlan_vid_del(slave_a_dev, proto, vid);
+
+	if (slave_b_dev)
+		vlan_vid_del(slave_b_dev, proto, vid);
+
+	return ret;
 }
 
 static int hsr_ndo_vlan_rx_kill_vid(struct net_device *dev,
-- 
2.53.0