renepay: fix double free of tal object

routefail object allocation was linked to route,
we had a crash of the plugin with the following error:

0x561f424fc07a send_backtrace
	common/daemon.c:33
0x561f424fc102 crashdump
	common/daemon.c:75
0x7f5b0e7dc04f ???
	???:0
0x7f5b0e82ae2c ???
	???:0
0x7f5b0e7dbfb1 ???
	???:0
0x7f5b0e7c6471 ???
	???:0
0x561f4252581f call_error
	ccan/ccan/tal/tal.c:95
0x561f425258c8 check_bounds
	ccan/ccan/tal/tal.c:169
0x561f425258f9 to_tal_hdr
	ccan/ccan/tal/tal.c:179
0x561f42526283 tal_free
	ccan/ccan/tal/tal.c:525
0x561f424e5379 routefail_end
	plugins/renepay/routefail.c:52
0x561f424e557b handle_failure
	plugins/renepay/routefail.c:431

apparently there was a race condition for which the route was first
freed before we arrived to routefail_end where we manually free
routefail. I don't see how this could have happened, but anyways
this subtle bug can be avoided by linking the routefail to the payment.

Signed-off-by: Lagrang3 <lagrang3@protonmail.com>

plugins/renepay/routefail.c

@@ -43,13 +43,14 @@ struct command_result *routefail_start(const tal_t *ctx, struct route *route,
 	return update_gossip(r);
 }
 
-static struct command_result *routefail_end(struct routefail *r)
+static struct command_result *routefail_end(struct routefail *r TAKES)
 {
 	/* Notify the tracker that route has failed and routefail have completed
 	 * handling all possible errors cases. */
 	struct command *cmd = r->cmd;
 	route_failure_register(r->payment->routetracker, r->route);
-	tal_free(r);
+	if (taken(r))
+		r = tal_steal(tmpctx, r);
 	return notification_handled(cmd);
 }
 
@@ -428,5 +429,5 @@ static struct command_result *handle_failure(struct routefail *r)
 
 		break;
 	}
-	return routefail_end(r);
+	return routefail_end(take(r));
 }

plugins/renepay/routetracker.c

@@ -402,7 +402,7 @@ struct command_result *notification_sendpay_failure(struct command *cmd,
 
 	/* we do some error processing steps before calling
 	 * route_failure_register. */
-	return routefail_start(route, route, cmd);
+	return routefail_start(payment, route, cmd);
 }
 
 struct command_result *notification_sendpay_success(struct command *cmd,