From 022ea5a872db0750e9f0f45d29d5dda4e0c35647 Mon Sep 17 00:00:00 2001
From: david gauchard <gauchard@laas.fr>
Date: Mon, 18 Dec 2017 12:56:18 +0100
Subject: [PATCH] consequence of ::flush() update: fix potential double free
 (#3990)

---
 libraries/ESP8266WiFi/src/include/UdpContext.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/libraries/ESP8266WiFi/src/include/UdpContext.h b/libraries/ESP8266WiFi/src/include/UdpContext.h
index cb527ab0a..95f342080 100644
--- a/libraries/ESP8266WiFi/src/include/UdpContext.h
+++ b/libraries/ESP8266WiFi/src/include/UdpContext.h
@@ -288,7 +288,8 @@ public:
                 data_size -= will_copy;
             }
         }
-        pbuf_free(_tx_buf_head);
+        if (_tx_buf_head)
+            pbuf_free(_tx_buf_head);
         _tx_buf_head = 0;
         _tx_buf_cur = 0;
         _tx_buf_offset = 0;