From 1e2d9309510de4b4337a2d842457b5c55717db29 Mon Sep 17 00:00:00 2001 From: Hao Wu Date: Mon, 20 Mar 2017 15:17:36 +0800 Subject: MdeModulePkg/ScsiDiskDxe: Fix undefined behavior in signed left shift In function GetMediaInfo(), the following expression: ScsiDiskDevice->BlkIo.Media->LastBlock = (Capacity10->LastLba3 << 24) | (Capacity10->LastLba2 << 16) | (Capacity10->LastLba1 << 8) | Capacity10->LastLba0; will involve undefined behavior in signed left shift operations. 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, 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 Capacity10->LastLba3 is 1, (Capacity10->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 ScsiDiskDevice->BlkIo.Media->LastBlock to 1 during the cast from type int to type UINT64. This commit will add an explicit UINT32 type cast for Capacity10->LastLba3 to resolve this issue. Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Hao Wu Reviewed-by: Feng Tian Reviewed-by: Laszlo Ersek (cherry picked from commit 7c115e775b439661b06e84edda0670098c81d354) --- MdeModulePkg/Bus/Scsi/ScsiDiskDxe/ScsiDisk.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'MdeModulePkg') 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.
+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 @@ -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; -- cgit v1.2.3