[PATCH net-next v1 1/4] net: hsr: serialize seq_blocks merge across nodes

luka.gejak
2026-03-24T14:35:29Z

During node merging, hsr_handle_sup_frame() walks node_curr->seq_blocks
to update node_real without holding node_curr->seq_out_lock. This
allows concurrent mutations from duplicate registration paths, risking
inconsistent state or XArray/bitmap corruption.

Fix this by locking both nodes' seq_out_lock during the merge.
To prevent ABBA deadlocks, locks are acquired in order of memory
address.

Signed-off-by: Luka Gejak <luka.gejak@linux.dev>
---
net/hsr/hsr_framereg.c | 38 ++++++++++++++++++++++++++++++++++++--
1 file changed, 36 insertions(+), 2 deletions(-)

diff --git a/net/hsr/hsr_framereg.c b/net/hsr/hsr_framereg.c
index 577fb588bc2f..d09875b33588 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);
--
2.53.0