From e5f4514847d3749c60b97a87bcda253c298a328a Mon Sep 17 00:00:00 2001
From: david gauchard <gauchard@laas.fr>
Date: Wed, 15 Apr 2020 20:22:02 +0200
Subject: [PATCH] mDNS: protect MDNSResponder::queryService against misuse
 (#7216)

* mDNS: protect MDNSResponder::queryService against misuse

* fix style
---
 libraries/ESP8266mDNS/src/LEAmDNS.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/libraries/ESP8266mDNS/src/LEAmDNS.cpp b/libraries/ESP8266mDNS/src/LEAmDNS.cpp
index 628432411..87ff5167f 100644
--- a/libraries/ESP8266mDNS/src/LEAmDNS.cpp
+++ b/libraries/ESP8266mDNS/src/LEAmDNS.cpp
@@ -767,6 +767,12 @@ uint32_t MDNSResponder::queryService(const char* p_pcService,
                                      const char* p_pcProtocol,
                                      const uint16_t p_u16Timeout /*= MDNS_QUERYSERVICES_WAIT_TIME*/)
 {
+    if (0 == m_pUDPContext)
+    {
+        // safeguard against misuse
+        return 0;
+    }
+
     DEBUG_EX_INFO(DEBUG_OUTPUT.printf_P(PSTR("[MDNSResponder] queryService '%s.%s'\n"), p_pcService, p_pcProtocol););
 
     uint32_t    u32Result = 0;