From: Mark Andrews <marka@isc.org>
Date: Fri, 4 Sep 2020 02:50:42 +0000 (+1000)
Subject: Address lock-order-inversion between the keytable and the db locks.
X-Git-Tag: v9.16.8~45^2~6
X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=f5a8d9055fd57f5c5e5cf6f463104c7085045fa1;p=thirdparty%2Fbind9.git

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)
---

diff --git a/lib/dns/zone.c b/lib/dns/zone.c
index 2b5856838b5..9f3008808f4 100644
--- a/lib/dns/zone.c
+++ b/lib/dns/zone.c
@@ -4518,7 +4518,11 @@ sync_keyzone(dns_zone_t *zone, dns_db_t *db) {
 		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 || !dns_keynode_managed(keynode)) {
 			CHECK(delete_keydata(db, ver, &diff, rrname, rdataset));