Detach the zone views outside of the zone lock

Detaching the views in the zone_shutdown() could lead to
lock-order-inversion between adb->namelocks[bucket], adb->lock,
view->lock and zone->lock.  Detach the views outside of the section that
zone-locked.

diff --git a/lib/dns/zone.c b/lib/dns/zone.c
index 411756d9cbe9cc3c3833be24ce3d064f799b8ab8..9cf2bd49f75a40bc5c3ccd0cbe6941aaa7bf60ee 100644 (file)
--- a/lib/dns/zone.c
+++ b/lib/dns/zone.c
@@ -14689,6 +14689,7 @@ zone_shutdown(void *arg) {
        dns_zone_t *zone = (dns_zone_t *)arg;
        bool free_needed, linked = false;
        dns_zone_t *raw = NULL, *secure = NULL;
+       dns_view_t *view = NULL, *prev_view = NULL;
 
        REQUIRE(DNS_ZONE_VALID(zone));
        INSIST(isc_refcount_current(&zone->erefs) == 0);
@@ -14734,13 +14735,15 @@ zone_shutdown(void *arg) {
        LOCK_ZONE(zone);
        INSIST(zone != zone->raw);
 
-       /* Detach the views early, we don't need them anymore */
-       if (zone->view != NULL) {
-               dns_view_weakdetach(&zone->view);
-       }
-       if (zone->prev_view != NULL) {
-               dns_view_weakdetach(&zone->prev_view);
-       }
+       /*
+        * Detach the views early, we don't need them anymore.  However, we need
+        * to detach them outside of the zone lock to break the lock loop
+        * between view, adb and zone locks.
+        */
+       view = zone->view;
+       zone->view = NULL;
+       prev_view = zone->prev_view;
+       zone->prev_view = NULL;
 
        if (linked) {
                isc_refcount_decrement(&zone->irefs);
@@ -14802,6 +14805,14 @@ zone_shutdown(void *arg) {
                zone->secure = NULL;
        }
        UNLOCK_ZONE(zone);
+
+       if (view != NULL) {
+               dns_view_weakdetach(&view);
+       }
+       if (prev_view != NULL) {
+               dns_view_weakdetach(&prev_view);
+       }
+
        if (raw != NULL) {
                dns_zone_detach(&raw);
        }