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From: Hao Wu <hao.a.wu@intel.com>
To: edk2-devel@lists.01.org
Cc: Hao Wu <hao.a.wu@intel.com>, Steven Shi <steven.shi@intel.com>,
	Star Zeng <star.zeng@intel.com>, Eric Dong <eric.dong@intel.com>
Subject: [PATCH 5/6] MdeModulePkg/Crc32: Fix possible out of range left shift
Date: Tue, 19 Sep 2017 19:43:50 +0800	[thread overview]
Message-ID: <20170919114351.18448-6-hao.a.wu@intel.com> (raw)
In-Reply-To: <20170919114351.18448-1-hao.a.wu@intel.com>

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=697

Within function ReverseBits(), left shift operations of 1 in the
following statements:
"(1 << Index)" and "(1 << (31 - Index))"

will incur possible out of range left shift when Index is either 0 or
31, since "1 << 31" is possible to exceed the range of type 'int'
(signed).

According to the C11 spec, Section 6.5.7:
> 4 The result of E1 << E2 is E1 left-shifted E2 bit positions; vacated
>   bits are filled with zeros. If E1 has an unsigned type, the value
>   of the result is E1 * 2^E2 , reduced modulo one more than the
>   maximum value representable in the result type. If E1 has a signed
>   type and nonnegative value, and E1 * 2^E2 is representable in the
>   result type, then that is the resulting value; otherwise, the
>   behavior is undefined.

This commit explicitly cast '1' with UINT32 to resolve this issue.

Cc: Steven Shi <steven.shi@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
---
 MdeModulePkg/Core/RuntimeDxe/Crc32.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/MdeModulePkg/Core/RuntimeDxe/Crc32.c b/MdeModulePkg/Core/RuntimeDxe/Crc32.c
index a6fe77fa34..5cee66ebd1 100644
--- a/MdeModulePkg/Core/RuntimeDxe/Crc32.c
+++ b/MdeModulePkg/Core/RuntimeDxe/Crc32.c
@@ -7,7 +7,7 @@
   EFI Runtime Services Table are converted from physical address to
   virtual addresses.  This requires that the 32-bit CRC be recomputed.
 
-Copyright (c) 2006 - 2008, 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
@@ -79,8 +79,8 @@ ReverseBits (
 
   NewValue = 0;
   for (Index = 0; Index < 32; Index++) {
-    if ((Value & (1 << Index)) != 0) {
-      NewValue = NewValue | (1 << (31 - Index));
+    if ((Value & (((UINT32)1) << Index)) != 0) {
+      NewValue = NewValue | (((UINT32)1) << (31 - Index));
     }
   }
 
-- 
2.12.0.windows.1



  parent reply	other threads:[~2017-09-19 11:41 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-09-19 11:43 [PATCH 0/6] Resolve undefined behaviours in left shift OPs Hao Wu
2017-09-19 11:43 ` [PATCH 1/6] MdePkg/PrintLib: Fix possible negative value left shift Hao Wu
2017-09-19 11:43 ` [PATCH 2/6] MdeModulePkg/PrintLib: " Hao Wu
2017-09-19 11:43 ` [PATCH 3/6] MdeModulePkg/Tpl: Fix " Hao Wu
2017-09-19 17:02   ` Paolo Bonzini
2017-09-21  2:57     ` Zeng, Star
2017-09-21  3:06       ` Wu, Hao A
2017-09-19 11:43 ` [PATCH 4/6] MdeModulePkg/DxeNetLib: " Hao Wu
2017-09-19 17:04   ` Paolo Bonzini
2017-09-21  5:38   ` Wu, Jiaxin
2017-09-19 11:43 ` Hao Wu [this message]
2017-09-19 17:05   ` [PATCH 5/6] MdeModulePkg/Crc32: Fix possible out of range " Paolo Bonzini
2017-09-21  1:30     ` Wu, Hao A
2017-09-19 11:43 ` [PATCH 6/6] MdeModulePkg/AtaAtapiPassThru: " Hao Wu

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