check null

Author: maikebing

common/mqtt_list.c

@@ -5,8 +5,9 @@
  * @LastEditTime: 2020-04-27 23:28:12
  * @Description: the following code references TencentOS tiny, please keep the author information and source code according to the license.
  */
+#include <stddef.h>
+#include "mqtt_list.h"
 
-# include "mqtt_list.h"
 
 static void _mqtt_list_add(mqtt_list_t *node, mqtt_list_t *prev, mqtt_list_t *next)
 {
@@ -43,9 +44,13 @@ void mqtt_list_add_tail(mqtt_list_t *node, mqtt_list_t *list)
     _mqtt_list_add(node, list->prev, list);
 }
 
-void mqtt_list_del(mqtt_list_t *entry)
+void mqtt_list_del(mqtt_list_t* entry)
 {
-    _mqtt_list_del(entry->prev, entry->next);
+	if (entry == NULL) return;
+	if (entry->prev == NULL || entry->next == NULL) return;
+	_mqtt_list_del(entry->prev, entry->next);
+	entry->prev = NULL;
+	entry->next = NULL;
 }
 
 void mqtt_list_del_init(mqtt_list_t *entry)

mqttclient/mqttclient.c

@@ -228,6 +228,8 @@ static int mqtt_is_topic_equals(const char *topic_filter, const char *topic)
     return 0;
 }
 
+// topic_filter: The filter string used in subscription (may contain +/#), e.g. a/+/c or foo/#
+// topic_name:   The actual topic received (should not contain wildcards), e.g. a/b/c or foo/bar
 static char mqtt_topic_is_matched(const char* topic_filter, MQTTString* topic_name)
 {
     const char* filter = topic_filter;
@@ -465,8 +467,14 @@ static message_handlers_t *mqtt_msg_handler_create(const char* topic_filter, mqt
 static void mqtt_msg_handler_destory(message_handlers_t *msg_handler)
 {
     if (NULL != &msg_handler->list) {
+    
+        if (msg_handler->list.prev == NULL || msg_handler->list.next == NULL) return;
+    
         mqtt_list_del(&msg_handler->list);
+        msg_handler->list.prev == NULL;
+        msg_handler->list.next == NULL;
         platform_memory_free(msg_handler);
+        msg_handler = NULL;
     }
 }