From fca6831ae481cbf911573eede3b7e6101cf32707 Mon Sep 17 00:00:00 2001 From: Hao Wu Date: Wed, 12 Apr 2017 08:43:10 +0800 Subject: IntelFrameworkModulePkg/IdeBusDxe: Fix undefined behavior in signed left shift In function AtapiReadCapacity(), the following expression: IdeDev->BlkIo.Media->LastBlock = (Data.LastLba3 << 24) | (Data.LastLba2 << 16) | (Data.LastLba1 << 8) | Data.LastLba0; (There is also a similar case in this function.) will involve undefined behavior in signed left shift operations. Since Data.LastLbaX is of type UINT8, and IdeDev->BlkIo.Media->LastBlock is of type UINT64. Therefore, Data.LastLbaX will be promoted to int (32 bits, signed) first, and then perform the left shift operation. 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. So if bit 7 of Data.LastLba3 is 1, (Data.LastLba3 << 24) will be out of the range within int type. The undefined behavior of the signed left shift will lead to a potential of setting the high 32 bits of IdeDev->BlkIo.Media->LastBlock to 1 during the cast from type int to type UINT64. This commit will add an explicit UINT32 type cast for Data.LastLba3 to resolve this issue. Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Hao Wu Reviewed-by: Feng Tian (cherry picked from commit f90c4fff00bee5f654ad93afd0f74b99050960de) --- IntelFrameworkModulePkg/Bus/Pci/IdeBusDxe/Atapi.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/IntelFrameworkModulePkg/Bus/Pci/IdeBusDxe/Atapi.c b/IntelFrameworkModulePkg/Bus/Pci/IdeBusDxe/Atapi.c index 1a3cb2e0a0..c641dc5714 100644 --- a/IntelFrameworkModulePkg/Bus/Pci/IdeBusDxe/Atapi.c +++ b/IntelFrameworkModulePkg/Bus/Pci/IdeBusDxe/Atapi.c @@ -1,7 +1,7 @@ /** @file This file contains all helper functions on the ATAPI command - Copyright (c) 2006 - 2010, Intel Corporation. All rights reserved.
+ Copyright (c) 2006 - 2017, Intel Corporation. All rights reserved.
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 @@ -1053,7 +1053,7 @@ AtapiReadCapacity ( if (!EFI_ERROR (Status) && *SResult == SenseNoSenseKey) { if (IdeDev->Type == IdeCdRom) { - IdeDev->BlkIo.Media->LastBlock = (Data.LastLba3 << 24) | + IdeDev->BlkIo.Media->LastBlock = ((UINT32) Data.LastLba3 << 24) | (Data.LastLba2 << 16) | (Data.LastLba1 << 8) | Data.LastLba0; @@ -1076,7 +1076,7 @@ AtapiReadCapacity ( IdeDev->BlkIo.Media->LastBlock = 0; } else { - IdeDev->BlkIo.Media->LastBlock = (FormatData.LastLba3 << 24) | + IdeDev->BlkIo.Media->LastBlock = ((UINT32) FormatData.LastLba3 << 24) | (FormatData.LastLba2 << 16) | (FormatData.LastLba1 << 8) | FormatData.LastLba0; -- cgit v1.2.3