Merge branch 'net-hsr-fixes-for-prp-duplication-and-vlan-unwind'

Luka Gejak says:

====================
net: hsr: fixes for PRP duplication and VLAN unwind

This series addresses two logic bugs in the HSR/PRP implementation
identified during a protocol audit. These are targeted for the 'net'
tree as they fix potential memory corruption and state inconsistency.

The primary change resolves a race condition in the node merging path by
implementing address-based lock ordering. This ensures that concurrent
mutations of sequence blocks do not lead to state corruption or
deadlocks.

An additional fix corrects asymmetric VLAN error unwinding by
implementing a centralized unwind path on slave errors.
====================

Link: https://patch.msgid.link/20260401092243.52121-1-luka.gejak@linux.dev
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

2 files changed, 53 insertions, 17 deletions

diff --git a/net/hsr/hsr_device.c b/net/hsr/hsr_device.c
index d1bfc49b5f01..fd2fea25eff0 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,
diff --git a/net/hsr/hsr_framereg.c b/net/hsr/hsr_framereg.c
index 50996f4de7f9..d41863593674 100644
--- a/net/hsr/hsr_framereg.c
+++ b/net/hsr/hsr_framereg.c
@@ -123,6 +123,40 @@ static void hsr_free_node_rcu(struct rcu_head *rn)
 	hsr_free_node(node);
 }
 
+static void hsr_lock_seq_out_pair(struct hsr_node *node_a,
+				  struct hsr_node *node_b)
+{
+	if (node_a == node_b) {
+		spin_lock_bh(&node_a->seq_out_lock);
+		return;
+	}
+
+	if (node_a < node_b) {
+		spin_lock_bh(&node_a->seq_out_lock);
+		spin_lock_nested(&node_b->seq_out_lock, SINGLE_DEPTH_NESTING);
+	} else {
+		spin_lock_bh(&node_b->seq_out_lock);
+		spin_lock_nested(&node_a->seq_out_lock, SINGLE_DEPTH_NESTING);
+	}
+}
+
+static void hsr_unlock_seq_out_pair(struct hsr_node *node_a,
+				    struct hsr_node *node_b)
+{
+	if (node_a == node_b) {
+		spin_unlock_bh(&node_a->seq_out_lock);
+		return;
+	}
+
+	if (node_a < node_b) {
+		spin_unlock(&node_b->seq_out_lock);
+		spin_unlock_bh(&node_a->seq_out_lock);
+	} else {
+		spin_unlock(&node_a->seq_out_lock);
+		spin_unlock_bh(&node_b->seq_out_lock);
+	}
+}
+
 void hsr_del_nodes(struct list_head *node_db)
 {
 	struct hsr_node *node;
@@ -432,7 +466,7 @@ void hsr_handle_sup_frame(struct hsr_frame_info *frame)
 	}
 
 	ether_addr_copy(node_real->macaddress_B, ethhdr->h_source);
-	spin_lock_bh(&node_real->seq_out_lock);
+	hsr_lock_seq_out_pair(node_real, node_curr);
 	for (i = 0; i < HSR_PT_PORTS; i++) {
 		if (!node_curr->time_in_stale[i] &&
 		    time_after(node_curr->time_in[i], node_real->time_in[i])) {
@@ -455,7 +489,7 @@ void hsr_handle_sup_frame(struct hsr_frame_info *frame)
 				  src_blk->seq_nrs[i], HSR_SEQ_BLOCK_SIZE);
 		}
 	}
-	spin_unlock_bh(&node_real->seq_out_lock);
+	hsr_unlock_seq_out_pair(node_real, node_curr);
 	node_real->addr_B_port = port_rcv->type;
 
 	spin_lock_bh(&hsr->list_lock);