From cd4b3c9004a3a5a85e7c966b4273c4a535204345 Mon Sep 17 00:00:00 2001
From: Star Zeng <star.zeng@intel.com>
Date: Mon, 15 Jan 2018 10:26:07 +0800
Subject: [PATCH] IntelSiliconPkg IntelVTdDxe: Fix potential NULL pointer
 dereference

The implementation of MdeModulePkg\Universal\Acpi\AcpiTableDxe reserves
first entry of RSDT/XSDT to FADT, the first entry value is 0 when FADT
is not installed. So the RSDT/XSDT parsing code should check the entry
value first before checking the table signature.

Cc: Jiewen Yao <jiewen.yao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
(cherry picked from commit 01bd1c98fa83ef4449798fcf206fbd40db97b2d6)
---
 IntelSiliconPkg/Feature/VTd/IntelVTdDxe/DmarAcpiTable.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/IntelSiliconPkg/Feature/VTd/IntelVTdDxe/DmarAcpiTable.c b/IntelSiliconPkg/Feature/VTd/IntelVTdDxe/DmarAcpiTable.c
index b981bcdb3a..342830a01f 100644
--- a/IntelSiliconPkg/Feature/VTd/IntelVTdDxe/DmarAcpiTable.c
+++ b/IntelSiliconPkg/Feature/VTd/IntelVTdDxe/DmarAcpiTable.c
@@ -1,6 +1,6 @@
 /** @file
 
-  Copyright (c) 2017, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2017 - 2018, 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
@@ -889,7 +889,7 @@ ScanTableInRSDT (
   EntryPtr = &Rsdt->Entry;
   for (Index = 0; Index < EntryCount; Index ++, EntryPtr ++) {
     Table = (EFI_ACPI_DESCRIPTION_HEADER*)((UINTN)(*EntryPtr));
-    if (Table->Signature == Signature) {
+    if ((Table != NULL) && (Table->Signature == Signature)) {
       return Table;
     }
   }
@@ -923,7 +923,7 @@ ScanTableInXSDT (
   for (Index = 0; Index < EntryCount; Index ++) {
     CopyMem (&EntryPtr, (VOID *)(BasePtr + Index * sizeof(UINT64)), sizeof(UINT64));
     Table = (EFI_ACPI_DESCRIPTION_HEADER*)((UINTN)(EntryPtr));
-    if (Table->Signature == Signature) {
+    if ((Table != NULL) && (Table->Signature == Signature)) {
       return Table;
     }
   }