[PATCH net 1/1] net: hsr: defer node table free until after RCU readers

[Michael Bommarito <michael.bommarito@gmail.com>]

HSR node-list and node-status generic-netlink operations run under
rcu_read_lock(). They walk hsr->node_db through hsr_get_next_node() and
hsr_get_node_data(), but RTM_DELLINK teardown removes the same node table
with plain list_del() and frees each node immediately.

That lets a generic-netlink reader hold a struct hsr_node pointer across
hsr_dellink(). In a KASAN build, widening the reader window after
hsr_get_next_node() obtains the node reproduces a slab-use-after-free
when the reader copies node->macaddress_A; the freeing stack is
hsr_del_nodes() from hsr_dellink().

Use list_del_rcu() and defer the free through the existing
hsr_free_node_rcu() callback. This matches the lifetime rule used by the
HSR prune paths, which already delete nodes with list_del_rcu() and
call_rcu().

Fixes: b9a1e627405d ("hsr: implement dellink to clean up resources")
Cc: stable@vger.kernel.org # v5.3+
Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com>
Assisted-by: Claude:claude-opus-4-7
---
 net/hsr/hsr_framereg.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/hsr/hsr_framereg.c b/net/hsr/hsr_framereg.c
index d09875b33588..06b0977ab099 100644
--- a/net/hsr/hsr_framereg.c
+++ b/net/hsr/hsr_framereg.c
@@ -163,8 +163,8 @@ void hsr_del_nodes(struct list_head *node_db)
 	struct hsr_node *tmp;
 
 	list_for_each_entry_safe(node, tmp, node_db, mac_list) {
-		list_del(&node->mac_list);
-		hsr_free_node(node);
+		list_del_rcu(&node->mac_list);
+		call_rcu(&node->rcu_head, hsr_free_node_rcu);
 	}
 }
 
-- 
2.53.0