Address lock-order-inversion

    WARNING: ThreadSanitizer: lock-order-inversion (potential deadlock)
    Cycle in lock order graph: M1 (0x000000000001) => M2 (0x000000000002) => M1

    Mutex M2 acquired here while holding mutex M1 in thread T1:
    #0 pthread_rwlock_wrlock <null>
    #1 isc_rwlock_lock lib/isc/rwlock.c:52:4
    #2 zone_postload lib/dns/zone.c:5101:2
    #3 receive_secure_db lib/dns/zone.c:16206:11
    #4 dispatch lib/isc/task.c:1152:7
    #5 run lib/isc/task.c:1344:2

    Mutex M1 previously acquired by the same thread here:
    #0 pthread_mutex_lock <null>
    #1 receive_secure_db lib/dns/zone.c:16204:2
    #2 dispatch lib/isc/task.c:1152:7
    #3 run lib/isc/task.c:1344:2

    Mutex M1 acquired here while holding mutex M2 in thread T1:
    #0 pthread_mutex_lock <null>
    #1 get_raw_serial lib/dns/zone.c:2518:2
    #2 zone_gotwritehandle lib/dns/zone.c:2559:4
    #3 dispatch lib/isc/task.c:1152:7
    #4 run lib/isc/task.c:1344:2

    Mutex M2 previously acquired by the same thread here:
    #0 pthread_rwlock_rdlock <null>
    #1 isc_rwlock_lock lib/isc/rwlock.c:48:3
    #2 zone_gotwritehandle lib/dns/zone.c:2552:2
    #3 dispatch lib/isc/task.c:1152:7
    #4 run lib/isc/task.c:1344:2

    Thread T1 (running) created by main thread at:
    #0 pthread_create <null>
    #1 isc_thread_create lib/isc/pthreads/thread.c:73:8
    #2 isc_taskmgr_create lib/isc/task.c:1434:3
    #3 create_managers bin/named/main.c:915:11
    #4 setup bin/named/main.c:1223:11
    #5 main bin/named/main.c:1523:2

    SUMMARY: ThreadSanitizer: lock-order-inversion (potential deadlock) in pthread_rwlock_wrlock

diff --git a/lib/dns/zone.c b/lib/dns/zone.c
index eb300e1bfc33f9a43ee5708ab1f97f970ff21f7e..fc522a90744d5b0ad502c65ba04d260c199e46c8 100644 (file)
--- a/lib/dns/zone.c
+++ b/lib/dns/zone.c
@@ -2534,6 +2534,7 @@ zone_gotwritehandle(isc_task_t *task, isc_event_t *event) {
        isc_result_t result = ISC_R_SUCCESS;
        dns_dbversion_t *version = NULL;
        dns_masterrawheader_t rawdata;
+       dns_db_t *db = NULL;
 
        REQUIRE(DNS_ZONE_VALID(zone));
        INSIST(task == zone->task);
@@ -2551,9 +2552,12 @@ zone_gotwritehandle(isc_task_t *task, isc_event_t *event) {
        INSIST(zone != zone->raw);
        ZONEDB_LOCK(&zone->dblock, isc_rwlocktype_read);
        if (zone->db != NULL) {
+               dns_db_attach(zone->db, &db);
+       }
+       ZONEDB_UNLOCK(&zone->dblock, isc_rwlocktype_read);
+       if (db != NULL) {
                const dns_master_style_t *output_style;
-
-               dns_db_currentversion(zone->db, &version);
+               dns_db_currentversion(db, &version);
                dns_master_initrawheader(&rawdata);
                if (inline_secure(zone)) {
                        get_raw_serial(zone->raw, &rawdata);
@@ -2566,14 +2570,16 @@ zone_gotwritehandle(isc_task_t *task, isc_event_t *event) {
                        output_style = &dns_master_style_default;
                }
                result = dns_master_dumpinc(
-                       zone->mctx, zone->db, version, output_style,
-                       zone->masterfile, zone->task, dump_done, zone,
-                       &zone->dctx, zone->masterformat, &rawdata);
-               dns_db_closeversion(zone->db, &version, false);
+                       zone->mctx, db, version, output_style, zone->masterfile,
+                       zone->task, dump_done, zone, &zone->dctx,
+                       zone->masterformat, &rawdata);
+               dns_db_closeversion(db, &version, false);
        } else {
                result = ISC_R_CANCELED;
        }
-       ZONEDB_UNLOCK(&zone->dblock, isc_rwlocktype_read);
+       if (db != NULL) {
+               dns_db_detach(&db);
+       }
        UNLOCK_ZONE(zone);
        if (result != DNS_R_CONTINUE) {
                goto fail;