From d52f9163debb523e06d49ed8a4627a0317bab92c Mon Sep 17 00:00:00 2001
From: Jiaxin Wu <jiaxin.wu@intel.com>
Date: Thu, 29 Dec 2016 15:57:39 +0800
Subject: MdeModulePkg/Ip4Dxe: Fix the potential NULL pointer free

Ip4Config2SetDnsServer may cause ASSERT if the invalid DNS
server address received. The issue is triggered by the NULL
pointer(Tmp) free.

Cc: Ye Ting <ting.ye@intel.com>
Cc: Fu Siyuan <siyuan.fu@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Wu Jiaxin <jiaxin.wu@intel.com>
Reviewed-by: Fu Siyuan <siyuan.fu@intel.com>
Reviewed-by: Ye Ting <ting.ye@intel.com>
---
 MdeModulePkg/Universal/Network/Ip4Dxe/Ip4Config2Impl.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/MdeModulePkg/Universal/Network/Ip4Dxe/Ip4Config2Impl.c b/MdeModulePkg/Universal/Network/Ip4Dxe/Ip4Config2Impl.c
index 88ead9d269..131b03f771 100644
--- a/MdeModulePkg/Universal/Network/Ip4Dxe/Ip4Config2Impl.c
+++ b/MdeModulePkg/Universal/Network/Ip4Dxe/Ip4Config2Impl.c
@@ -1,7 +1,7 @@
 /** @file
   The implementation of EFI IPv4 Configuration II Protocol.
 
-  Copyright (c) 2015 - 2016, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2015 - 2017, Intel Corporation. All rights reserved.<BR>
   (C) Copyright 2015-2016 Hewlett Packard Enterprise Development LP<BR>
 
   This program and the accompanying materials
@@ -741,13 +741,17 @@ Ip4Config2SetDnsServerWorker (
       //
       // The dns server address must be unicast.
       //
-      FreePool (Tmp);
+      if (Tmp != NULL) {
+        FreePool (Tmp);
+      }
       return EFI_INVALID_PARAMETER;
     }
 
     for (Index1 = NewIndex + 1; Index1 < NewDnsCount; Index1++) {
       if (EFI_IP4_EQUAL (NewDns + NewIndex, NewDns + Index1)) {
-        FreePool (Tmp);
+        if (Tmp != NULL) {
+          FreePool (Tmp);
+        }
         return EFI_INVALID_PARAMETER;
       }
     }
-- 
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