FAILED: patch "[PATCH] net: hsr: defer node table free until after RCU readers" failed to apply to 6.1-stable tree

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x aaec7096f9961eb223b5b149abe9495525c205d9
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026052840-statistic-envoy-e450@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From aaec7096f9961eb223b5b149abe9495525c205d9 Mon Sep 17 00:00:00 2001
From: Michael Bommarito <[email protected]>
Date: Wed, 13 May 2026 19:38:38 -0400
Subject: [PATCH] net: hsr: defer node table free until after RCU readers

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().

index 124619920d38..b514e43766ef 100644
@@ -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);
 	}
 }
 

From: Michael Bommarito <[email protected]>

[ Upstream commit aaec7096f9961eb223b5b149abe9495525c205d9 ]

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().

---
 net/hsr/hsr_framereg.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

index e44a039e36afe..fec8dd8460568 100644
@@ -121,8 +121,10 @@ void hsr_del_nodes(struct list_head *node_db)
 	struct hsr_node *node;
 	struct hsr_node *tmp;
 
-	list_for_each_entry_safe(node, tmp, node_db, mac_list)
-		kfree(node);
+	list_for_each_entry_safe(node, tmp, node_db, mac_list) {
+		list_del_rcu(&node->mac_list);
+		kfree_rcu(node, rcu_head);
+	}
 }
 
 void prp_handle_san_frame(bool san, enum hsr_port_type port,

2.53.0