From 7f6cddad0ca1b19c50a04a2f6568e9a9c4129504 Mon Sep 17 00:00:00 2001
From: Mark Andrews <marka@isc.org>
Date: Fri, 4 Sep 2020 12:50:42 +1000
Subject: [PATCH] Address lock-order-inversion between the keytable and the db
 locks.

    WARNING: ThreadSanitizer: lock-order-inversion (potential deadlock)
    Cycle in lock order graph: M1 (0x000000000000) => M2 (0x000000000000) => M1

    Mutex M2 acquired here while holding mutex M1 in thread T1:
    #0 pthread_rwlock_rdlock <null>
    #1 isc_rwlock_lock lib/isc/rwlock.c:48:3
    #2 dns_keytable_find lib/dns/keytable.c:522:2
    #3 sync_keyzone lib/dns/zone.c:4560:12
    #4 dns_zone_synckeyzone lib/dns/zone.c:4635:11
    #5 mkey_refresh bin/named/server.c:15423:2
    #6 named_server_mkeys bin/named/server.c:15727:4
    #7 named_control_docommand bin/named/control.c:236:12
    #8 control_command bin/named/controlconf.c:365:17
    #9 dispatch lib/isc/task.c:1152:7
    #10 run lib/isc/task.c:1344:2

    Mutex M1 previously acquired by the same thread here:
    #0 pthread_rwlock_rdlock <null>
    #1 isc_rwlock_lock lib/isc/rwlock.c:48:3
    #2 resume_iteration lib/dns/rbtdb.c:9357:2
    #3 dbiterator_first lib/dns/rbtdb.c:9407:3
    #4 dns_dbiterator_first lib/dns/dbiterator.c:43:10
    #5 dns_rriterator_first lib/dns/rriterator.c:71:15
    #6 sync_keyzone lib/dns/zone.c:4543:16
    #7 dns_zone_synckeyzone lib/dns/zone.c:4635:11
    #8 mkey_refresh bin/named/server.c:15423:2
    #9 named_server_mkeys bin/named/server.c:15727:4
    #10 named_control_docommand bin/named/control.c:236:12
    #11 control_command bin/named/controlconf.c:365:17
    #12 dispatch lib/isc/task.c:1152:7
    #13 run lib/isc/task.c:1344:2

    Mutex M1 acquired here while holding mutex M2 in thread T1:
    #0 pthread_rwlock_rdlock <null>
    #1 isc_rwlock_lock lib/isc/rwlock.c:48:3
    #2 zone_find lib/dns/rbtdb.c:4029:2
    #3 dns_db_find lib/dns/db.c:500:11
    #4 addifmissing lib/dns/zone.c:4481:11
    #5 dns_keytable_forall lib/dns/keytable.c:786:4
    #6 sync_keyzone lib/dns/zone.c:4586:2
    #7 dns_zone_synckeyzone lib/dns/zone.c:4635:11
    #8 mkey_refresh bin/named/server.c:15423:2
    #9 named_server_mkeys bin/named/server.c:15727:4
    #10 named_control_docommand bin/named/control.c:236:12
    #11 control_command bin/named/controlconf.c:365:17
    #12 dispatch lib/isc/task.c:1152:7
    #13 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 dns_keytable_forall lib/dns/keytable.c:770:2
    #3 sync_keyzone lib/dns/zone.c:4586:2
    #4 dns_zone_synckeyzone lib/dns/zone.c:4635:11
    #5 mkey_refresh bin/named/server.c:15423:2
    #6 named_server_mkeys bin/named/server.c:15727:4
    #7 named_control_docommand bin/named/control.c:236:12
    #8 control_command bin/named/controlconf.c:365:17
    #9 dispatch lib/isc/task.c:1152:7
    #10 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_rdlock

(cherry picked from commit 9e5f83c4993310f9841a4eba90d4a84dba882727)
Conflict: NA
Reference: https://gitlab.isc.org/isc-projects/bind9/-/commit/7f6cddad0ca1b19c50a04a2f6568e9a9c4129504
---
 lib/dns/zone.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/lib/dns/zone.c b/lib/dns/zone.c
index 4d5f7fb9a5..e120dded9e 100644
--- a/lib/dns/zone.c
+++ b/lib/dns/zone.c
@@ -4344,9 +4344,14 @@ sync_keyzone(dns_zone_t *zone, dns_db_t *db) {
 			goto failure;
 		}
 
-		if (rdataset->type != dns_rdatatype_keydata)
+		if (rdataset->type != dns_rdatatype_keydata) {
 			continue;
-
+		}
+		/*
+		 * Release db wrlock to prevent LOR reports against
+		 * dns_keytable_forall() call below.
+		 */
+		dns_rriterator_pause(&rrit);
 		result = dns_keytable_find(sr, rrname, &keynode);
 		if ((result != ISC_R_SUCCESS &&
 		     result != DNS_R_PARTIALMATCH) ||
-- 
2.23.0

