[Patch 2/2] NetworkPkg/Ip6Dxe: Fix the potential NULL pointer free

[Jiaxin Wu <jiaxin.wu@intel.com>]

Ip6ConfigSetDnsServer 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>
---
 NetworkPkg/Ip6Dxe/Ip6ConfigImpl.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/NetworkPkg/Ip6Dxe/Ip6ConfigImpl.c b/NetworkPkg/Ip6Dxe/Ip6ConfigImpl.c
index 9b6a62e..4e881fd 100644
--- a/NetworkPkg/Ip6Dxe/Ip6ConfigImpl.c
+++ b/NetworkPkg/Ip6Dxe/Ip6ConfigImpl.c
@@ -1,9 +1,9 @@
 /** @file
   The implementation of EFI IPv6 Configuration Protocol.
 
-  Copyright (c) 2009 - 2016, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2009 - 2017, Intel Corporation. All rights reserved.<BR>
 
   This program and the accompanying materials
   are licensed and made available under the terms and conditions of the BSD License
   which accompanies this distribution.  The full text of the license may be found at
   http://opensource.org/licenses/bsd-license.php.
@@ -1364,17 +1364,21 @@ Ip6ConfigSetDnsServer (
 
     if (!NetIp6IsValidUnicast (NewDns + NewIndex)) {
       //
       // 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_IP6_EQUAL (NewDns + NewIndex, NewDns + Index1)) {
-        FreePool (Tmp);
+        if (Tmp != NULL) {
+          FreePool (Tmp);
+        }
         return EFI_INVALID_PARAMETER;
       }
     }
 
     if (OneAdded) {
-- 
1.9.5.msysgit.1