f Error on checked add

The only way we could overflow here is if we actually read an update at u64::MAX, and that is no longer allowed to happen, so this is an error.

Author: domZippilli

lightning/src/util/persist.rs

@@ -413,10 +413,10 @@ where
 			// ...parse and apply the updates with an id higher than the monitor.
 			let mut current_update_id = monitor.get_latest_update_id();
 			loop {
-				current_update_id = match current_update_id.checked_add(1) {
-					Some(next_update_id) => next_update_id,
-					None => break,
-				};
+				current_update_id = current_update_id.checked_add(1).ok_or(io::Error::new(
+					io::ErrorKind::Other,
+					"invalid update found at u64::MAX",
+				))?;
 				let update_name = UpdateName::from(current_update_id);
 				let update = match self.read_monitor_update(&monitor_name, &update_name) {
 					Ok(update) => update,
@@ -619,7 +619,7 @@ where
 					let mut end = monitor.get_latest_update_id();
 					// Typically, we'll clean up between the last two known full monitors. We
 					// shouldn't bother cleaning up if the update_id difference is less than or
-					// equal to one, since that implies no updates would be there. 
+					// equal to one, since that implies no updates would be there.
 					if end - start > 1 {
 						if monitor.get_latest_update_id() == CLOSED_CHANNEL_UPDATE_ID {
 							// We don't want to clean the rest of u64, so just do possible pending updates