* [PATCH net v2 1/1] net: l2tp: do not propagate multicast notification errors
[not found] <cover.1787247008.git.zihanx@nebusec.ai>
@ 2026-08-20 18:40 ` Zihan Xi
2026-08-24 11:21 ` Simon Horman
0 siblings, 1 reply; 2+ messages in thread
From: Zihan Xi @ 2026-08-20 18:40 UTC (permalink / raw)
To: netdev; +Cc: davem, edumazet, kuba, pabeni, horms, Zihan Xi, stable, Vega
The tunnel create, tunnel modify, session create, and session modify
netlink handlers send multicast notifications through helpers that can fail
while allocating or encoding a message, or while multicasting it.
For tunnel and session create/modify, a notification is sent after the live
operation has completed. Returning a best-effort notification error as the
command result can therefore report failure for an operation that already
committed and can cause callers to retry and accumulate live objects.
Keep sending notifications for listener visibility, but do not propagate
their best-effort status as the command result. This also keeps the tunnel
modify command consistent with the other notification-only paths.
Fixes: 33f72e6f0c67 ("l2tp : multicast notification to the registered listeners")
Cc: stable@vger.kernel.org
Reported-by: Vega <vega@nebusec.ai>
Assisted-by: Codex:gpt-5.4
Signed-off-by: Zihan Xi <zihanx@nebusec.ai>
---
changes in v2:
- Extend best-effort notification handling to tunnel_modify.
- Follow the existing bare-call style instead of explicit (void) casts.
- Document the observed ENOBUFS and committed-state reproduction.
- v1 Link: https://lore.kernel.org/all/cover.1786962220.git.zihanx@nebusec.ai/
net/l2tp/l2tp_netlink.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
diff --git a/net/l2tp/l2tp_netlink.c b/net/l2tp/l2tp_netlink.c
index 59457c0c1..fbdd3d055 100644
--- a/net/l2tp/l2tp_netlink.c
+++ b/net/l2tp/l2tp_netlink.c
@@ -248,8 +248,8 @@ static int l2tp_nl_cmd_tunnel_create(struct sk_buff *skb, struct genl_info *info
kfree(tunnel);
goto out;
}
- ret = l2tp_tunnel_notify(&l2tp_nl_family, info, tunnel,
- L2TP_CMD_TUNNEL_CREATE);
+ l2tp_tunnel_notify(&l2tp_nl_family, info, tunnel,
+ L2TP_CMD_TUNNEL_CREATE);
l2tp_tunnel_put(tunnel);
out:
@@ -305,8 +305,8 @@ static int l2tp_nl_cmd_tunnel_modify(struct sk_buff *skb, struct genl_info *info
goto out;
}
- ret = l2tp_tunnel_notify(&l2tp_nl_family, info,
- tunnel, L2TP_CMD_TUNNEL_MODIFY);
+ l2tp_tunnel_notify(&l2tp_nl_family, info,
+ tunnel, L2TP_CMD_TUNNEL_MODIFY);
l2tp_tunnel_put(tunnel);
@@ -645,8 +645,8 @@ static int l2tp_nl_cmd_session_create(struct sk_buff *skb, struct genl_info *inf
session = l2tp_session_get(net, tunnel->sock, tunnel->version,
tunnel_id, session_id);
if (session) {
- ret = l2tp_session_notify(&l2tp_nl_family, info, session,
- L2TP_CMD_SESSION_CREATE);
+ l2tp_session_notify(&l2tp_nl_family, info, session,
+ L2TP_CMD_SESSION_CREATE);
l2tp_session_put(session);
}
}
@@ -710,8 +710,8 @@ static int l2tp_nl_cmd_session_modify(struct sk_buff *skb, struct genl_info *inf
if (info->attrs[L2TP_ATTR_RECV_TIMEOUT])
session->reorder_timeout = nla_get_msecs(info->attrs[L2TP_ATTR_RECV_TIMEOUT]);
- ret = l2tp_session_notify(&l2tp_nl_family, info,
- session, L2TP_CMD_SESSION_MODIFY);
+ l2tp_session_notify(&l2tp_nl_family, info,
+ session, L2TP_CMD_SESSION_MODIFY);
l2tp_session_put(session);
--
2.43.0
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