From e1982d4ca9c7f337e6055fcb38931bd96f3f9903 Mon Sep 17 00:00:00 2001
From: sfu5 <sfu5@6f19259b-4bc3-4df7-8a09-765794883524>
Date: Wed, 23 Nov 2011 05:05:12 +0000
Subject: [PATCH] Add pointer check for NULL before dereference it.

Signed-off-by: sfu5
Reviewed-by: gdong1
Reviewed-by : czhan46

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@12764 6f19259b-4bc3-4df7-8a09-765794883524
---
 MdeModulePkg/Universal/Network/Dhcp4Dxe/Dhcp4Io.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/MdeModulePkg/Universal/Network/Dhcp4Dxe/Dhcp4Io.c b/MdeModulePkg/Universal/Network/Dhcp4Dxe/Dhcp4Io.c
index 65ab5ac702..b3ac646446 100644
--- a/MdeModulePkg/Universal/Network/Dhcp4Dxe/Dhcp4Io.c
+++ b/MdeModulePkg/Universal/Network/Dhcp4Dxe/Dhcp4Io.c
@@ -1621,7 +1621,9 @@ DhcpOnTimerTick (
         goto END_SESSION;
       }
 
-      Instance->ElaspedTime= 0;
+      if (Instance != NULL) {
+        Instance->ElaspedTime= 0;
+      }      
       
       Status = DhcpSendMessage (
                  DhcpSb,
@@ -1643,7 +1645,9 @@ DhcpOnTimerTick (
         goto END_SESSION;
       }
 
-      Instance->ElaspedTime= 0;
+      if (Instance != NULL) {
+        Instance->ElaspedTime= 0;
+      }    
 
       Status = DhcpSendMessage (
                  DhcpSb,