From: Michał Kępień <michal@isc.org>
Date: Thu, 15 Feb 2018 19:31:54 +0000 (+0100)
Subject: Do not recheck DNS_ZONEFLG_LOADPENDING in zone_asyncload()
X-Git-Tag: v9.12.1rc1~4^2~1
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=840c9348bfaf2de03423dece1ec1493a26d71e30;p=thirdparty%2Fbind9.git

Do not recheck DNS_ZONEFLG_LOADPENDING in zone_asyncload()

Remove a block of code which dates back to commit 8a2ab2b9203, when
dns_zone_asyncload() did not yet check DNS_ZONEFLG_LOADPENDING.
Currently, no race in accessing DNS_ZONEFLG_LOADPENDING is possible any
more, because:

  - dns_zone_asyncload() is still the only function which may queue
    zone_asyncload(),

  - dns_zone_asyncload() accesses DNS_ZONEFLG_LOADPENDING under a lock
    (and potentially queues an event under the same lock),

  - DNS_ZONEFLG_LOADPENDING is not cleared until the load actually
    completes.

Thus, the rechecking code can be safely removed from zone_asyncload().

Note that this also brings zone_asyncload() to a state in which the
completion callback is always invoked.  This is required to prevent
leaking memory in case something goes wrong in zone_asyncload() and a
zone table the zone belongs to is indefinitely left with a positive
reference count.
---

diff --git a/lib/dns/zone.c b/lib/dns/zone.c
index c4147d19af7..fe3aa71a850 100644
--- a/lib/dns/zone.c
+++ b/lib/dns/zone.c
@@ -2169,7 +2169,6 @@ zone_asyncload(isc_task_t *task, isc_event_t *event) {
 	dns_asyncload_t *asl = event->ev_arg;
 	dns_zone_t *zone = asl->zone;
 	isc_result_t result;
-	isc_boolean_t load_pending;
 
 	UNUSED(task);
 
@@ -2177,17 +2176,8 @@ zone_asyncload(isc_task_t *task, isc_event_t *event) {
 
 	isc_event_free(&event);
 
-	/* Make sure load is still pending */
 	LOCK_ZONE(zone);
-	load_pending = ISC_TF(DNS_ZONE_FLAG(zone, DNS_ZONEFLG_LOADPENDING));
-
-	if (!load_pending) {
-		UNLOCK_ZONE(zone);
-		goto cleanup;
-	}
-
 	result = zone_load(zone, 0, ISC_TRUE);
-
 	if (result != DNS_R_CONTINUE) {
 		DNS_ZONE_CLRFLAG(zone, DNS_ZONEFLG_LOADPENDING);
 	}
@@ -2197,7 +2187,6 @@ zone_asyncload(isc_task_t *task, isc_event_t *event) {
 	if (asl->loaded != NULL)
 		(asl->loaded)(asl->loaded_arg, zone, task);
 
- cleanup:
 	isc_mem_put(zone->mctx, asl, sizeof (*asl));
 	dns_zone_idetach(&zone);
 }