notify/out: use RCU_lock to protect from SOA change during event

src/knot/events/handlers/notify.c

@@ -15,6 +15,7 @@
  */
 
 #include <assert.h>
+#include <urcu.h>
 
 #include "contrib/openbsd/siphash.h"
 #include "knot/common/log.h"
@@ -150,7 +151,13 @@ int event_notify(conf_t *conf, zone_t *zone)
 
 	// NOTIFY content
 	int timeout = conf->cache.srv_tcp_remote_io_timeout;
+	rcu_read_lock();
 	knot_rrset_t soa = node_rrset(zone->contents->apex, KNOT_RRTYPE_SOA);
+	knot_rrset_t *soa_cpy = knot_rrset_copy(&soa, NULL);
+	rcu_read_unlock();
+	if (soa_cpy == NULL) {
+		return KNOT_ENOMEM;
+	}
 
 	// in case of re-try, NOTIFY only failed remotes
 	pthread_mutex_lock(&zone->preferred_lock);
@@ -175,7 +182,7 @@ int event_notify(conf_t *conf, zone_t *zone)
 
 		for (int i = 0; i < addr_count; i++) {
 			conf_remote_t slave = conf_remote(conf, iter.id, i);
-			ret = send_notify(conf, zone, &soa, &slave, timeout, retry);
+			ret = send_notify(conf, zone, soa_cpy, &slave, timeout, retry);
 			if (ret == KNOT_EOK) {
 				break;
 			}
@@ -195,7 +202,7 @@ int event_notify(conf_t *conf, zone_t *zone)
 	if (failed) {
 		notifailed_rmt_dynarray_sort_dedup(&zone->notifailed);
 
-		uint32_t retry_in = knot_soa_retry(soa.rrs.rdata);
+		uint32_t retry_in = knot_soa_retry(soa_cpy->rrs.rdata);
 		conf_val_t val = conf_zone_get(conf, C_RETRY_MIN_INTERVAL, zone->name);
 		retry_in = MAX(retry_in, conf_int(&val));
 		val = conf_zone_get(conf, C_RETRY_MAX_INTERVAL, zone->name);
@@ -204,6 +211,7 @@ int event_notify(conf_t *conf, zone_t *zone)
 		zone_events_schedule_at(zone, ZONE_EVENT_NOTIFY, time(NULL) + retry_in);
 	}
 	pthread_mutex_unlock(&zone->preferred_lock);
+	knot_rrset_free(soa_cpy, NULL);
 
 	return failed ? KNOT_ERROR : KNOT_EOK;
 }

tests-extra/tests/ctl/notify_x_upd/test.py

+#!/usr/bin/env python3
+
+'''Test of crash when NOTIFY is sent during zone CTL update.'''
+
+from dnstest.utils import *
+from dnstest.test import Test
+import random
+import threading
+import time
+
+loop_stop = False
+
+def background_notify(server, zone_name):
+    try:
+        server.ctl("zone-notify " + zone_name)
+    except:
+        pass
+
+def background_notify_loop(server, zone_name):
+    global loop_stop
+    while not loop_stop:
+        background_notify(server, zone_name)
+
+def run_thr(fun, server, zone_name):
+    threading.Thread(target=fun, args=[server, zone_name]).start()
+
+t = Test()
+
+master = t.server("knot")
+slave = t.server("knot")
+zones = t.zone_rnd(1, dnssec=False, records=40)
+t.link(zones, master, slave)
+ZONE = zones[0].name
+
+t.start()
+serials = slave.zones_wait(zones)
+
+try:
+    run_thr(background_notify_loop, master, ZONE)
+
+    for i in range(10):
+        master.ctl("zone-begin " + ZONE)
+        master.ctl("zone-set %s dhowedhhjewodw 3600 A 1.2.3.%d" % (ZONE, i + 1))
+        master.ctl("zone-commit " + ZONE)
+finally:
+    loop_stop = True
+
+t.end()