From 2d39bcba7d8b76d4bee1c76f3ba878d6c3ad1b2b Mon Sep 17 00:00:00 2001
From: Zhenyu Wu <Adam5Wu@users.noreply.github.com>
Date: Fri, 23 Mar 2018 14:01:17 -0400
Subject: [PATCH] Resolve updater size check bug (#4550)

---
 cores/esp8266/Updater.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/cores/esp8266/Updater.cpp b/cores/esp8266/Updater.cpp
index 2a93d96d7..e01eca0bc 100644
--- a/cores/esp8266/Updater.cpp
+++ b/cores/esp8266/Updater.cpp
@@ -86,7 +86,7 @@ bool UpdaterClass::begin(size_t size, int command) {
     //size of the update rounded to a sector
     uint32_t roundedSize = (size + FLASH_SECTOR_SIZE - 1) & (~(FLASH_SECTOR_SIZE - 1));
     //address where we will start writing the update
-    updateStartAddress = updateEndAddress - roundedSize;
+    updateStartAddress = (updateEndAddress > roundedSize)? (updateEndAddress - roundedSize) : 0;
 
 #ifdef DEBUG_UPDATER
         DEBUG_UPDATER.printf("[begin] roundedSize:       0x%08X (%d)\n", roundedSize, roundedSize);
@@ -390,4 +390,4 @@ void UpdaterClass::printError(Print &out){
   }
 }
 
-UpdaterClass Update;
\ No newline at end of file
+UpdaterClass Update;