From 28bb419edcaaaaeea67e4332de8aea0078adf3d7 Mon Sep 17 00:00:00 2001
From: Aram Sargsyan <aram@isc.org>
Date: Tue, 4 Jul 2023 08:38:39 +0000
Subject: [PATCH] Add shutdown checks in dns_catz_dbupdate_callback()

When a zone database update callback is called, the 'catzs' object,
extracted from the callback argument, might be already shutting down,
in which case the 'catzs->zones' can be NULL and cause an assertion
failure when calling isc_ht_find().

Add an early return from the callback if 'catzs->shuttingdown' is true.

Also check the validity of 'catzs->zones' after locking 'catzs' in
case there is a race with dns_catz_shutdown_catzs() running in another
thread.
---
 lib/dns/catz.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/lib/dns/catz.c b/lib/dns/catz.c
index 4dfa2fac3e..c58b727de0 100644
--- a/lib/dns/catz.c
+++ b/lib/dns/catz.c
@@ -2137,9 +2137,17 @@ dns_catz_dbupdate_callback(dns_db_t *db, void *fn_arg) {
 	REQUIRE(DNS_CATZ_ZONES_VALID(fn_arg));
 	catzs = (dns_catz_zones_t *)fn_arg;
 
+	if (atomic_load(&catzs->shuttingdown)) {
+		return (ISC_R_SHUTTINGDOWN);
+	}
+
 	dns_name_toregion(&db->origin, &r);
 
 	LOCK(&catzs->lock);
+	if (catzs->zones == NULL) {
+		result = ISC_R_SHUTTINGDOWN;
+		goto cleanup;
+	}
 	result = isc_ht_find(catzs->zones, r.base, r.length, (void **)&catz);
 	if (result != ISC_R_SUCCESS) {
 		goto cleanup;