commit 3a2ea636103eaf40404fb82f228605d384c36434
Author: Mark Andrews <marka@isc.org>
Date:   Tue Dec 17 09:08:59 2013 +1100

    3692.   [bug]           Two calls to dns_db_getoriginnode were fatal if there
                            was no data at the node. [RT #35080]
    
    (cherry picked from commit 161e803a5608956271d8120be37a1b383d14b647)

diff --git a/lib/dns/rbtdb.c b/lib/dns/rbtdb.c
index 2dd4aa0..941b77e 100644
--- a/lib/dns/rbtdb.c
+++ b/lib/dns/rbtdb.c
@@ -1638,8 +1638,11 @@ decrement_reference(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node,
 
 	nodelock = &rbtdb->node_locks[bucket];
 
+#define KEEP_NODE(n, r) \
+	((n)->data != NULL || (n)->down != NULL || (n) == (r)->origin_node)
+
 	/* Handle easy and typical case first. */
-	if (!node->dirty && (node->data != NULL || node->down != NULL)) {
+	if (!node->dirty && KEEP_NODE(node, rbtdb)) {
 		dns_rbtnode_refdecrement(node, &nrefs);
 		INSIST((int)nrefs >= 0);
 		if (nrefs == 0) {
@@ -1708,12 +1711,11 @@ decrement_reference(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node,
 	isc_refcount_decrement(&nodelock->references, &refs);
 	INSIST((int)refs >= 0);
 
-	/*
-	 * XXXDCL should this only be done for cache zones?
-	 */
-	if (node->data != NULL || node->down != NULL)
+	if (KEEP_NODE(node, rbtdb))
 		goto restore_locks;
 
+#undef KEEP_NODE
+
 	if (write_locked) {
 		/*
 		 * We can now delete the node.