From: Michał Kępień <michal@isc.org>
Date: Mon, 24 Sep 2018 17:33:16 +0000 (+0200)
Subject: Prevent a race after zone load
X-Git-Tag: v9.11.5rc1~5^2~1
X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=74cd632f18758d40cf93bdc64b413234fc911ee3;p=thirdparty%2Fbind9.git

Prevent a race after zone load

Zone loading happens in a different task (zone->loadtask) than other
zone actions (zone->task).  Thus, when zone_postload() is called in the
context of zone->loadtask, it may cause zone maintenance to be queued in
zone->task and another thread can then execute zone_maintenance() before
zone_postload() gets a chance to finish its work in the first thread.
This would not be a problem if zone_maintenance() accounted for this
possibility by locking the zone before checking the state of its
DNS_ZONEFLG_LOADPENDING flag.  However, the zone is currently not locked
before the state of that flag is checked, which may prevent zone
maintenance from happening despite zone_postload() scheduling it.  Fix
by locking the zone in zone_maintenance() before checking the state of
the zone's DNS_ZONEFLG_LOADPENDING flag.

(cherry picked from commit 56003e9f9f72c8be67d553f4dbd16eba849ca864)
---

diff --git a/lib/dns/zone.c b/lib/dns/zone.c
index eff8c32a8ec..94a8c0ea12a 100644
--- a/lib/dns/zone.c
+++ b/lib/dns/zone.c
@@ -9989,7 +9989,7 @@ zone_maintenance(dns_zone_t *zone) {
 	const char me[] = "zone_maintenance";
 	isc_time_t now;
 	isc_result_t result;
-	bool dumping;
+	bool dumping, load_pending;
 
 	REQUIRE(DNS_ZONE_VALID(zone));
 	ENTER;
@@ -9997,8 +9997,13 @@ zone_maintenance(dns_zone_t *zone) {
 	/*
 	 * Are we pending load/reload?
 	 */
-	if (DNS_ZONE_FLAG(zone, DNS_ZONEFLG_LOADPENDING))
+	LOCK_ZONE(zone);
+	load_pending = DNS_ZONE_FLAG(zone, DNS_ZONEFLG_LOADPENDING);
+	UNLOCK_ZONE(zone);
+
+	if (load_pending) {
 		return;
+	}
 
 	/*
 	 * Configuring the view of this zone may have