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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