[PATCH net v3 1/2] tipc: guard against empty list in tipc_node_xmit()

[Weiming Shi <bestswngs@gmail.com>]

tipc_node_xmit() passes @list to tipc_lxc_xmit(), which dereferences
buf_msg(skb_peek(list)) without checking, so an empty list causes a NULL
pointer dereference. named_distribute() can hand it an empty list when a
bulk allocation fails. tipc_link_xmit() was already guarded in commit
b77413446408 ("tipc: fix NULL deref in tipc_link_xmit()"); guard
tipc_node_xmit() itself so the tipc_lxc_xmit() path is covered too.

Fixes: f73b12812a3d ("tipc: improve throughput between nodes in netns")
Reported-by: Xiang Mei <xmei5@asu.edu>
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Weiming Shi <bestswngs@gmail.com>
---
 net/tipc/node.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/tipc/node.c b/net/tipc/node.c
index 97aa970a0d83..fc241e7b0c1f 100644
--- a/net/tipc/node.c
+++ b/net/tipc/node.c
@@ -1695,6 +1695,9 @@ int tipc_node_xmit(struct net *net, struct sk_buff_head *list,
 	int bearer_id;
 	int rc;
 
+	if (skb_queue_empty(list))
+		return 0;
+
 	if (in_own_node(net, dnode)) {
 		tipc_loopback_trace(net, list);
 		spin_lock_init(&list->lock);
-- 
2.43.0