From b337f966e85ec2ae65769ee6bab12f78edcfafa5 Mon Sep 17 00:00:00 2001
From: Michael Sweet <michael.r.sweet@gmail.com>
Date: Mon, 28 Aug 2017 10:04:29 -0400
Subject: [PATCH] Fix an Avahi-related crash bug in the scheduler (Issue #5085,
 Issue #5086)

Add NULL pointer check to avoid Avahi assertion in production code.
---
 CHANGES.md         |  1 +
 scheduler/dirsvc.c | 13 ++++++++-----
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/CHANGES.md b/CHANGES.md
index 5ac9ec1072..2dbd33ff18 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -26,6 +26,7 @@ CHANGES IN CUPS V2.2.5
   values (Issue #5074)
 - The scheduler now creates a PID file when not running on demand with a modern
   service launcher (Issue #5080)
+- Fixed an Avahi-related crash bug in the scheduler (Issue #5085, Issue #5086)
 - The IPP Everywhere PPD generator now sorts the supported resolutions before
   choosing them for draft, normal, and best quality modes (Issue #5091)
 - Fixed an issue with Chinese localizations on macOS (rdar://32419311)
diff --git a/scheduler/dirsvc.c b/scheduler/dirsvc.c
index 6f6aa8bb44..2308e05384 100644
--- a/scheduler/dirsvc.c
+++ b/scheduler/dirsvc.c
@@ -699,13 +699,16 @@ dnssdDeregisterInstance(
   DNSServiceRefDeallocate(*srv);
 
 #  else /* HAVE_AVAHI */
-  if (!from_callback)
-    avahi_threaded_poll_lock(DNSSDMaster);
+  if (*srv)
+  {
+    if (!from_callback)
+      avahi_threaded_poll_lock(DNSSDMaster);
 
-  avahi_entry_group_free(*srv);
+    avahi_entry_group_free(*srv);
 
-  if (!from_callback)
-    avahi_threaded_poll_unlock(DNSSDMaster);
+    if (!from_callback)
+      avahi_threaded_poll_unlock(DNSSDMaster);
+  }
 #  endif /* HAVE_DNSSD */
 
   *srv = NULL;