From f7682a18977ca5144561eea59f85cef08bfa27e3 Mon Sep 17 00:00:00 2001
From: "Roger A. Light" <roger@atchoo.org>
Date: Tue, 10 Aug 2021 20:48:21 +0100
Subject: [PATCH] Bug #575314

---
 lib/property_mosq.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/lib/property_mosq.c b/lib/property_mosq.c
index 0cfc9f9c..ada66204 100644
--- a/lib/property_mosq.c
+++ b/lib/property_mosq.c
@@ -959,14 +959,16 @@ int mosquitto_property_check_all(int command, const mosquitto_property *properti
 		if(rc) return rc;
 
 		/* Check for duplicates */
-		tail = p->next;
-		while(tail){
-			if(p->identifier == tail->identifier
-					&& p->identifier != MQTT_PROP_USER_PROPERTY){
+		if(p->identifier != MQTT_PROP_USER_PROPERTY){
+			tail = p->next;
+			while(tail){
+				if(p->identifier == tail->identifier
+						&& p->identifier != MQTT_PROP_USER_PROPERTY){
 
-				return MOSQ_ERR_DUPLICATE_PROPERTY;
+					return MOSQ_ERR_DUPLICATE_PROPERTY;
+				}
+				tail = tail->next;
 			}
-			tail = tail->next;
 		}
 
 		p = p->next;
-- 
2.30.2