File _service:obs_scm:backport-CVE-2023-1981.patch of Package avahi

From a2696da2f2c50ac43b6c4903f72290d5c3fa9f6f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Petr=20Men=C5=A1=C3=ADk?= <pemensik@redhat.com>
Date: Thu, 17 Nov 2022 01:51:53 +0100
Subject: [PATCH] Emit error if requested service is not found

It currently just crashes instead of replying with error. Check return
value and emit error instead of passing NULL pointer to reply.

Fixes #375
---
 avahi-daemon/dbus-protocol.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/avahi-daemon/dbus-protocol.c b/avahi-daemon/dbus-protocol.c
index 70d7687bc..406d0b441 100644
--- a/avahi-daemon/dbus-protocol.c
+++ b/avahi-daemon/dbus-protocol.c
@@ -375,10 +375,14 @@ static DBusHandlerResult dbus_get_alternative_host_name(DBusConnection *c, DBusM
     }
 
     t = avahi_alternative_host_name(n);
-    avahi_dbus_respond_string(c, m, t);
-    avahi_free(t);
+    if (t) {
+        avahi_dbus_respond_string(c, m, t);
+        avahi_free(t);
 
-    return DBUS_HANDLER_RESULT_HANDLED;
+        return DBUS_HANDLER_RESULT_HANDLED;
+    } else {
+        return avahi_dbus_respond_error(c, m, AVAHI_ERR_NOT_FOUND, "Hostname not found");
+    }
 }
 
 static DBusHandlerResult dbus_get_alternative_service_name(DBusConnection *c, DBusMessage *m, DBusError *error) {
@@ -389,10 +393,14 @@ static DBusHandlerResult dbus_get_alternative_service_name(DBusConnection *c, DB
     }
 
     t = avahi_alternative_service_name(n);
-    avahi_dbus_respond_string(c, m, t);
-    avahi_free(t);
+    if (t) {
+        avahi_dbus_respond_string(c, m, t);
+        avahi_free(t);
 
-    return DBUS_HANDLER_RESULT_HANDLED;
+        return DBUS_HANDLER_RESULT_HANDLED;
+    } else {
+        return avahi_dbus_respond_error(c, m, AVAHI_ERR_NOT_FOUND, "Service not found");
+    }
 }
 
 static DBusHandlerResult dbus_create_new_entry_group(DBusConnection *c, DBusMessage *m, DBusError *error) {