Re: [PATCH v2 5/6] MdeModulePkg/Crc32: Fix possible out of range left shift

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

Got it. I will send a new series to drop this patch.


Best Regards,
Hao Wu

> -----Original Message-----
> From: Gao, Liming
> Sent: Thursday, September 28, 2017 11:54 AM
> To: Wu, Hao A; edk2-devel@lists.01.org
> Cc: Wu, Hao A; Paolo Bonzini; Dong, Eric; Zeng, Star
> Subject: RE: [edk2] [PATCH v2 5/6] MdeModulePkg/Crc32: Fix possible out of
> range left shift
> 
> Hao:
>   I sent another patch to introduce CacluateCrc32() API in BaseLib. It will update
> MdeModulePkg Crc32 to depend on BaseLib. And, BaseLib CacluateCrc32() has
> no such logic. So, I think this patch is not necessary.
> 
> Thanks
> Liming
> >-----Original Message-----
> >From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Hao
> >Wu
> >Sent: Thursday, September 21, 2017 2:46 PM
> >To: edk2-devel@lists.01.org
> >Cc: Wu, Hao A <hao.a.wu@intel.com>; Paolo Bonzini <pbonzini@redhat.com>;
> >Dong, Eric <eric.dong@intel.com>; Zeng, Star <star.zeng@intel.com>
> >Subject: [edk2] [PATCH v2 5/6] MdeModulePkg/Crc32: Fix possible out of
> >range left shift
> >
> >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 uses '1U' instead of '1' 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>
> >Cc: Paolo Bonzini <pbonzini@redhat.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..2cd234b562 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 & (1U << Index)) != 0) {
> >+      NewValue = NewValue | (1U << (31 - Index));
> >     }
> >   }
> >
> >--
> >2.12.0.windows.1
> >
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