Reviewed-by: Jian J Wang <jian.j.w...@intel.com> > -----Original Message----- > From: Ni, Ruiyu > Sent: Friday, February 02, 2018 6:48 PM > To: edk2-devel@lists.01.org > Cc: Yao, Jiewen <jiewen....@intel.com>; Gao, Liming <liming....@intel.com>; > Wang, Jian J <jian.j.w...@intel.com> > Subject: [PATCH] MdePkg/SafeString: Directly return when length of source > string is 0 > > Today's implementation of [Ascii]StrnCpyS/[Ascii]StrnCatS doesn't > directly return the the length of source string is 0. > > When length of source string is 0, it means the Source points to > a memory that shouldn't be deferenced at all. > So it's not proper to call StrnLenS() in such situation. > In a pool guard enabled environment, when using shell to edit an > existing file which contains empty line, the page fault is met. > > The patch fixes the four library functions to align to the behavior > of non-safe version: directly return when length of source string > is 0. > > Contributed-under: TianoCore Contribution Agreement 1.1 > Signed-off-by: Ruiyu Ni <ruiyu...@intel.com> > Cc: Jiewen Yao <jiewen....@intel.com> > Cc: Liming Gao <liming....@intel.com> > Cc: Jian J Wang <jian.j.w...@intel.com> > --- > MdePkg/Library/BaseLib/SafeString.c | 18 +++++++++++++++++- > 1 file changed, 17 insertions(+), 1 deletion(-) > > diff --git a/MdePkg/Library/BaseLib/SafeString.c > b/MdePkg/Library/BaseLib/SafeString.c > index 68c33e9b7b..fed818ef33 100644 > --- a/MdePkg/Library/BaseLib/SafeString.c > +++ b/MdePkg/Library/BaseLib/SafeString.c > @@ -1,7 +1,7 @@ > /** @file > Safe String functions. > > - Copyright (c) 2014 - 2017, Intel Corporation. All rights reserved.<BR> > + Copyright (c) 2014 - 2018, 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 > @@ -317,6 +317,10 @@ StrnCpyS ( > { > UINTN SourceLen; > > + if (Length == 0) { > + return RETURN_SUCCESS; > + } > + > ASSERT (((UINTN) Destination & BIT0) == 0); > ASSERT (((UINTN) Source & BIT0) == 0); > > @@ -515,6 +519,10 @@ StrnCatS ( > UINTN CopyLen; > UINTN SourceLen; > > + if (Length == 0) { > + return RETURN_SUCCESS; > + } > + > ASSERT (((UINTN) Destination & BIT0) == 0); > ASSERT (((UINTN) Source & BIT0) == 0); > > @@ -1894,6 +1902,10 @@ AsciiStrnCpyS ( > { > UINTN SourceLen; > > + if (Length == 0) { > + return RETURN_SUCCESS; > + } > + > // > // 1. Neither Destination nor Source shall be a null pointer. > // > @@ -2082,6 +2094,10 @@ AsciiStrnCatS ( > UINTN CopyLen; > UINTN SourceLen; > > + if (Length == 0) { > + return RETURN_SUCCESS; > + } > + > // > // Let CopyLen denote the value DestMax - AsciiStrnLenS(Destination, > DestMax) upon entry to AsciiStrnCatS. > // > -- > 2.16.1.windows.1
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