[Patch] MdeModulePkg/DxeNetLib: Add array range check in NetIp6IsNetEqual().

[Wang Fan <fan.wang@intel.com>]

* The library API use array elements without any index range check, this
  patch is to fix this issue to avoid null pointer reference.

Cc: Fu Siyuan <siyuan.fu@intel.com>
Cc: Jiaxin Wu <jiaxin.wu@intel.com>
Cc: Hao Wu <hao.a.wu@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Wang Fan <fan.wang@intel.com>
---
 MdeModulePkg/Library/DxeNetLib/DxeNetLib.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c b/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c
index cbce28f..34e11a8 100644
--- a/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c
+++ b/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c
@@ -840,10 +840,14 @@ NetIp6IsNetEqual (
   }
 
   if (Bit > 0) {
     Mask = (UINT8) (0xFF << (8 - Bit));
 
+    ASSERT (Byte < 16);
+    if (Byte >= 16) {
+      return FALSE;
+    }
     if ((Ip1->Addr[Byte] & Mask) != (Ip2->Addr[Byte] & Mask)) {
       return FALSE;
     }
   }
 
-- 
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