[PATCH net v3 1/1] net: hsr: limit node table growth

[Ren Wei <n05ec@lzu.edu.cn>]

From: Haoze Xie <royenheart@gmail.com>

The HSR/PRP node learning paths allocate one persistent entry per
previously unseen source MAC. Since learned entries stay alive until the
prune timer catches up, the node tables can otherwise grow without a
bound under high churn of learned senders.

Limit the number of learned entries in each node table and stop adding
new ones once the configured limit is reached. This keeps node-table
resource use bounded across the affected learning paths.

Fixes: f421436a591d ("net/hsr: Add support for the High-availability Seamless Redundancy protocol (HSRv0)")
Fixes: 451d8123f897 ("net: prp: add packet handling support")
Cc: stable@kernel.org
Reported-by: Yuan Tan <yuantan098@gmail.com>
Reported-by: Yifan Wu <yifanwucs@gmail.com>
Reported-by: Juefei Pu <tomapufckgml@gmail.com>
Reported-by: Xin Liu <bird@lzu.edu.cn>
Tested-by: Yuqi Xu <xuyuqiabc@gmail.com>
Signed-off-by: Haoze Xie <royenheart@gmail.com>
Signed-off-by: Ren Wei <n05ec@lzu.edu.cn>
---
changes in v3:
- replace the v2 learning-suppression approach with direct node-table growth limiting
- add a node_table_size module parameter and stop learning new entries once each table reaches the configured limit
- fix the full-table handling so failed learning returns NULL instead of reusing an existing node
- v2 Link: https://lore.kernel.org/all/b053e938014c9bac22f7f687ecc2970f23a2b74a.1775281843.git.royenheart@gmail.com/

changes in v2:
- generalize the fix beyond PRP SAN traffic and cover HSR/PRP tagged sender floods
- decide whether learning is needed from local-exclusive delivery instead of protocol-specific SAN checks
- use the normal NULL return semantics from hsr_get_node() instead of ERR_PTR-based error plumbing
- skip duplicate-discard state checks when no node state exists
- v1 Link: https://lore.kernel.org/all/9c88b4b7844f867d065e7a7aba28b2c026386168.1775056603.git.royenheart@outlook.com/

 net/hsr/hsr_framereg.c | 26 ++++++++++++++++++++++----
 1 file changed, 22 insertions(+), 4 deletions(-)

diff --git a/net/hsr/hsr_framereg.c b/net/hsr/hsr_framereg.c
index d09875b33588..8a5a2a54a81f 100644
--- a/net/hsr/hsr_framereg.c
+++ b/net/hsr/hsr_framereg.c
@@ -14,12 +14,18 @@
 #include <kunit/visibility.h>
 #include <linux/if_ether.h>
 #include <linux/etherdevice.h>
+#include <linux/moduleparam.h>
 #include <linux/slab.h>
 #include <linux/rculist.h>
 #include "hsr_main.h"
 #include "hsr_framereg.h"
 #include "hsr_netlink.h"
 
+static unsigned int hsr_node_table_size = 1024;
+module_param_named(node_table_size, hsr_node_table_size, uint, 0644);
+MODULE_PARM_DESC(node_table_size,
+		 "Maximum number of learned entries in each HSR/PRP node table (0 = unlimited)");
+
 bool hsr_addr_is_redbox(struct hsr_priv *hsr, unsigned char *addr)
 {
 	if (!hsr->redbox || !is_valid_ether_addr(hsr->macaddress_redbox))
@@ -189,6 +195,7 @@ static struct hsr_node *hsr_add_node(struct hsr_priv *hsr,
 				     enum hsr_port_type rx_port)
 {
 	struct hsr_node *new_node, *node = NULL;
+	unsigned int node_count = 0;
 	unsigned long now;
 	size_t block_sz;
 	int i;
@@ -226,20 +233,31 @@ static struct hsr_node *hsr_add_node(struct hsr_priv *hsr,
 	spin_lock_bh(&hsr->list_lock);
 	list_for_each_entry_rcu(node, node_db, mac_list,
 				lockdep_is_held(&hsr->list_lock)) {
+		node_count++;
 		if (ether_addr_equal(node->macaddress_A, addr))
-			goto out;
+			goto out_found;
 		if (ether_addr_equal(node->macaddress_B, addr))
-			goto out;
+			goto out_found;
 	}
+
+	if (hsr_node_table_size && node_count >= hsr_node_table_size)
+		goto out_drop;
 	list_add_tail_rcu(&new_node->mac_list, node_db);
 	spin_unlock_bh(&hsr->list_lock);
 	return new_node;
-out:
+out_found:
 	spin_unlock_bh(&hsr->list_lock);
+	xa_destroy(&new_node->seq_blocks);
 	kfree(new_node->block_buf);
-free:
 	kfree(new_node);
 	return node;
+out_drop:
+	spin_unlock_bh(&hsr->list_lock);
+	xa_destroy(&new_node->seq_blocks);
+	kfree(new_node->block_buf);
+free:
+	kfree(new_node);
+	return NULL;
 }
 
 void prp_update_san_info(struct hsr_node *node, bool is_sup)
-- 
2.53.0