ShellPkg: acpiview: SLIT: Validate global pointer before use

Check if SlitSystemLocalityCount pointer has been successfully updated
before it is used for further table parsing.

Signed-off-by: Krzysztof Koch <krzysztof.koch@arm.com>

1 files changed, 14 insertions, 2 deletions

diff --git a/ShellPkg/Library/UefiShellAcpiViewCommandLib/Parsers/Slit/SlitParser.c b/ShellPkg/Library/UefiShellAcpiViewCommandLib/Parsers/Slit/SlitParser.c
index ca2808db52..17e2166a09 100644
--- a/ShellPkg/Library/UefiShellAcpiViewCommandLib/Parsers/Slit/SlitParser.c
+++ b/ShellPkg/Library/UefiShellAcpiViewCommandLib/Parsers/Slit/SlitParser.c
@@ -1,7 +1,7 @@
 /** @file

   SLIT table parser

 

-  Copyright (c) 2016 - 2018, ARM Limited. All rights reserved.

+  Copyright (c) 2016 - 2019, ARM Limited. All rights reserved.

   SPDX-License-Identifier: BSD-2-Clause-Patent

 

   @par Reference(s):

@@ -75,9 +75,21 @@ ParseAcpiSlit (
              AcpiTableLength,

              PARSER_PARAMS (SlitParser)

              );

-  LocalityPtr = Ptr + Offset;

 

+  // Check if the values used to control the parsing logic have been

+  // successfully read.

+  if (SlitSystemLocalityCount == NULL) {

+    IncrementErrorCount ();

+    Print (

+      L"ERROR: Insufficient table length. AcpiTableLength = %d.\n",

+      AcpiTableLength

+      );

+    return;

+  }

+

+  LocalityPtr = Ptr + Offset;

   LocalityCount = *SlitSystemLocalityCount;

+

   // We only print the Localities if the count is less than 16

   // If the locality count is more than 16 then refer to the

   // raw data dump.