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Fix potential peer_state deadlocks in finish_force_close_channel #2597

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merged 2 commits into from
Sep 26, 2023
Merged

Fix potential peer_state deadlocks in finish_force_close_channel #2597

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d6cd197
Fix potential peer_state deadlocks in `finish_force_close_channel`
TheBlueMatt Sep 25, 2023
20e1c27
Provide some test coverage of `shutdown` msgs for unfunded chans
TheBlueMatt Sep 25, 2023
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46 changes: 34 additions & 12 deletions lightning/src/ln/channelmanager.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2626,8 +2626,13 @@ where
self.close_channel_internal(channel_id, counterparty_node_id, target_feerate_sats_per_1000_weight, shutdown_script)
}

#[inline]
fn finish_force_close_channel(&self, shutdown_res: ShutdownResult) {
debug_assert_ne!(self.per_peer_state.held_by_thread(), LockHeldState::HeldByThread);
#[cfg(debug_assertions)]
for (_, peer) in self.per_peer_state.read().unwrap().iter() {
debug_assert_ne!(peer.held_by_thread(), LockHeldState::HeldByThread);
}

let (monitor_update_option, mut failed_htlcs) = shutdown_res;
log_debug!(self.logger, "Finishing force-closure of channel with {} HTLCs to fail", failed_htlcs.len());
for htlc_source in failed_htlcs.drain(..) {
Expand All @@ -2653,8 +2658,7 @@ where
let peer_state_mutex = per_peer_state.get(peer_node_id)
.ok_or_else(|| APIError::ChannelUnavailable { err: format!("Can't find a peer matching the passed counterparty node_id {}", peer_node_id) })?;
let (update_opt, counterparty_node_id) = {
let mut peer_state_lock = peer_state_mutex.lock().unwrap();
let peer_state = &mut *peer_state_lock;
let mut peer_state = peer_state_mutex.lock().unwrap();
let closure_reason = if let Some(peer_msg) = peer_msg {
ClosureReason::CounterpartyForceClosed { peer_msg: UntrustedString(peer_msg.to_string()) }
} else {
Expand All @@ -2664,6 +2668,8 @@ where
log_error!(self.logger, "Force-closing channel {}", channel_id);
self.issue_channel_close_events(&chan_phase_entry.get().context(), closure_reason);
let mut chan_phase = remove_channel_phase!(self, chan_phase_entry);
mem::drop(peer_state);
mem::drop(per_peer_state);
match chan_phase {
ChannelPhase::Funded(mut chan) => {
self.finish_force_close_channel(chan.context.force_shutdown(broadcast));
Expand All @@ -2686,10 +2692,17 @@ where
}
};
if let Some(update) = update_opt {
let mut peer_state = peer_state_mutex.lock().unwrap();
peer_state.pending_msg_events.push(events::MessageSendEvent::BroadcastChannelUpdate {
msg: update
});
// Try to send the `BroadcastChannelUpdate` to the peer we just force-closed on, but if
// not try to broadcast it via whatever peer we have.
let per_peer_state = self.per_peer_state.read().unwrap();
let a_peer_state_opt = per_peer_state.get(peer_node_id)
.ok_or(per_peer_state.values().next());
if let Ok(a_peer_state_mutex) = a_peer_state_opt {
let mut a_peer_state = a_peer_state_mutex.lock().unwrap();
a_peer_state.pending_msg_events.push(events::MessageSendEvent::BroadcastChannelUpdate {
msg: update
});
}
}

Ok(counterparty_node_id)
Expand Down Expand Up @@ -4627,8 +4640,9 @@ where
let mut handle_errors: Vec<(Result<(), _>, _)> = Vec::new();
let mut timed_out_mpp_htlcs = Vec::new();
let mut pending_peers_awaiting_removal = Vec::new();
let mut shutdown_channels = Vec::new();

let process_unfunded_channel_tick = |
let mut process_unfunded_channel_tick = |
chan_id: &ChannelId,
context: &mut ChannelContext<SP>,
unfunded_context: &mut UnfundedChannelContext,
Expand All @@ -4641,7 +4655,7 @@ where
"Force-closing pending channel with ID {} for not establishing in a timely manner", chan_id);
update_maps_on_chan_removal!(self, &context);
self.issue_channel_close_events(&context, ClosureReason::HolderForceClosed);
self.finish_force_close_channel(context.force_shutdown(false));
shutdown_channels.push(context.force_shutdown(false));
pending_msg_events.push(MessageSendEvent::HandleError {
node_id: counterparty_node_id,
action: msgs::ErrorAction::SendErrorMessage {
Expand Down Expand Up @@ -4834,6 +4848,10 @@ where
let _ = handle_error!(self, err, counterparty_node_id);
}

for shutdown_res in shutdown_channels {
self.finish_force_close_channel(shutdown_res);
}

self.pending_outbound_payments.remove_stale_payments(&self.pending_events);

// Technically we don't need to do this here, but if we have holding cell entries in a
Expand Down Expand Up @@ -4990,6 +5008,7 @@ where
// This ensures that future code doesn't introduce a lock-order requirement for
// `forward_htlcs` to be locked after the `per_peer_state` peer locks, which calling
// this function with any `per_peer_state` peer lock acquired would.
#[cfg(debug_assertions)]
for (_, peer) in self.per_peer_state.read().unwrap().iter() {
debug_assert_ne!(peer.held_by_thread(), LockHeldState::HeldByThread);
}
Expand Down Expand Up @@ -5997,7 +6016,8 @@ where
}

fn internal_shutdown(&self, counterparty_node_id: &PublicKey, msg: &msgs::Shutdown) -> Result<(), MsgHandleErrInternal> {
let mut dropped_htlcs: Vec<(HTLCSource, PaymentHash)>;
let mut dropped_htlcs: Vec<(HTLCSource, PaymentHash)> = Vec::new();
let mut finish_shutdown = None;
{
let per_peer_state = self.per_peer_state.read().unwrap();
let peer_state_mutex = per_peer_state.get(counterparty_node_id)
Expand Down Expand Up @@ -6042,8 +6062,7 @@ where
log_error!(self.logger, "Immediately closing unfunded channel {} as peer asked to cooperatively shut it down (which is unnecessary)", &msg.channel_id);
self.issue_channel_close_events(&context, ClosureReason::CounterpartyCoopClosedUnfundedChannel);
let mut chan = remove_channel_phase!(self, chan_phase_entry);
self.finish_force_close_channel(chan.context_mut().force_shutdown(false));
return Ok(());
finish_shutdown = Some(chan.context_mut().force_shutdown(false));
},
}
} else {
Expand All @@ -6055,6 +6074,9 @@ where
let reason = HTLCFailReason::from_failure_code(0x4000 | 8);
self.fail_htlc_backwards_internal(&htlc_source.0, &htlc_source.1, &reason, receiver);
}
if let Some(shutdown_res) = finish_shutdown {
self.finish_force_close_channel(shutdown_res);
}

Ok(())
}
Expand Down
22 changes: 22 additions & 0 deletions lightning/src/ln/shutdown_tests.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -253,6 +253,28 @@ fn test_lnd_bug_6039() {
assert!(nodes[0].node.list_channels().is_empty());
}

#[test]
fn shutdown_on_unfunded_channel() {
// Test receiving a shutdown prior to funding generation
let chanmon_cfgs = create_chanmon_cfgs(2);
let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
let nodes = create_network(2, &node_cfgs, &node_chanmgrs);

nodes[0].node.create_channel(nodes[1].node.get_our_node_id(), 1_000_000, 100_000, 0, None).unwrap();
let open_chan = get_event_msg!(nodes[0], MessageSendEvent::SendOpenChannel, nodes[1].node.get_our_node_id());

// P2WSH
let script = Builder::new().push_int(0)
.push_slice(&[0; 20])
.into_script();
Comment on lines +267 to +270
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Nit: P2WPKH*

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🤦 Will fix in #2591


nodes[0].node.handle_shutdown(&nodes[1].node.get_our_node_id(), &msgs::Shutdown {
channel_id: open_chan.temporary_channel_id, scriptpubkey: script,
});
check_closed_event!(nodes[0], 1, ClosureReason::CounterpartyCoopClosedUnfundedChannel, [nodes[1].node.get_our_node_id()], 1_000_000);
}

#[test]
fn expect_channel_shutdown_state_with_force_closure() {
// Test sending a shutdown prior to channel_ready after funding generation
Expand Down