[PATCH] MdeModulePkg/ScsiDiskDxe: Fix potential implicit sign extension

[Hao Wu <hao.a.wu@intel.com>]

In function GetMediaInfo(), the following expression:
ScsiDiskDevice->BlkIo.Media->LastBlock =  (Capacity10->LastLba3 << 24) |
                                          (Capacity10->LastLba2 << 16) |
                                          (Capacity10->LastLba1 << 8)  |
                                           Capacity10->LastLba0;
will involve implicit sign extension.

Since Capacity10->LastLbaX is of type UINT8, and
ScsiDiskDevice->BlkIo.Media->LastBlock is of type UINT64. Therefore,
Capacity10->LastLbaX will be promoted to int (32 bits, signed) first,
perform the bit shift and or. Then the result will be sign-extended to
type UINT64.

If bit 7 of Capacity10->LastLba3 is 1, then the high 32 bits of
ScsiDiskDevice->BlkIo.Media->LastBlock will all be set to 1.

This commit will add an explicit UINT32 type cast for
Capacity10->LastLba3 to resolve this issue.

Cc: Feng Tian <feng.tian@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
---
 MdeModulePkg/Bus/Scsi/ScsiDiskDxe/ScsiDisk.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/MdeModulePkg/Bus/Scsi/ScsiDiskDxe/ScsiDisk.c b/MdeModulePkg/Bus/Scsi/ScsiDiskDxe/ScsiDisk.c
index b5eff25b9b..2289f20152 100644
--- a/MdeModulePkg/Bus/Scsi/ScsiDiskDxe/ScsiDisk.c
+++ b/MdeModulePkg/Bus/Scsi/ScsiDiskDxe/ScsiDisk.c
@@ -1,7 +1,7 @@
 /** @file
   SCSI disk driver that layers on every SCSI IO protocol in the system.
 
-Copyright (c) 2006 - 2016, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2006 - 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
@@ -2754,7 +2754,7 @@ GetMediaInfo (
   UINT8       *Ptr;
 
   if (!ScsiDiskDevice->Cdb16Byte) {
-    ScsiDiskDevice->BlkIo.Media->LastBlock =  (Capacity10->LastLba3 << 24) |
+    ScsiDiskDevice->BlkIo.Media->LastBlock =  ((UINT32) Capacity10->LastLba3 << 24) |
                                               (Capacity10->LastLba2 << 16) |
                                               (Capacity10->LastLba1 << 8)  |
                                                Capacity10->LastLba0;
-- 
2.12.0.windows.1