Re: [PATCH V2 3/3] DuetPkg FsVariable: Update GetNextVariableName to follow UEFI 2.7

["Ni, Ruiyu" <ruiyu.ni@intel.com>]

Star,
What's the benefit of this check "VariableName[MaxLen - 1] != 0"?
I think this check "StrnLenS (VariableName, MaxLen) == MaxLen" should be enough.

Thanks/Ray

> -----Original Message-----
> From: Zeng, Star
> Sent: Friday, June 23, 2017 4:08 PM
> To: edk2-devel@lists.01.org
> Cc: Zeng, Star <star.zeng@intel.com>; Gao, Liming <liming.gao@intel.com>;
> Ni, Ruiyu <ruiyu.ni@intel.com>
> Subject: [PATCH V2 3/3] DuetPkg FsVariable: Update GetNextVariableName
> to follow UEFI 2.7
> 
> "The size must be large enough to fit input string supplied in
> VariableName buffer" is added in the description for VariableNameSize.
> And two cases of EFI_INVALID_PARAMETER are added.
> 1. The input values of VariableName and VendorGuid are not a name and
>    GUID of an existing variable.
> 2. Null-terminator is not found in the first VariableNameSize bytes of
>    the input VariableName buffer.
> 
> This patch is to update code to follow them.
> 
> Cc: Liming Gao <liming.gao@intel.com>
> Cc: Ruiyu Ni <ruiyu.ni@intel.com>
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Star Zeng <star.zeng@intel.com>
> ---
>  DuetPkg/FSVariable/FSVariable.c | 21 ++++++++++++++++++++-
>  1 file changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/DuetPkg/FSVariable/FSVariable.c
> b/DuetPkg/FSVariable/FSVariable.c
> index 34b79305c871..6069cfa8fb98 100644
> --- a/DuetPkg/FSVariable/FSVariable.c
> +++ b/DuetPkg/FSVariable/FSVariable.c
> @@ -6,7 +6,7 @@ disk. They can be changed by user. BIOS is not able to
> protoect those.
>  Duet trusts all meta data from disk. If variable code, variable metadata and
> variable
>  data is modified in inproper way, the behavior is undefined.
> 
> -Copyright (c) 2006 - 2016, 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
> @@ -1400,14 +1400,33 @@ Returns:
>    VARIABLE_POINTER_TRACK  Variable;
>    UINTN                   VarNameSize;
>    EFI_STATUS              Status;
> +  UINTN                   MaxLen;
> 
>    if (VariableNameSize == NULL || VariableName == NULL || VendorGuid ==
> NULL) {
>      return EFI_INVALID_PARAMETER;
>    }
> 
> +  //
> +  // Calculate the possible maximum length of name string, including the Null
> terminator.
> +  //
> +  MaxLen = *VariableNameSize / sizeof (CHAR16);
> +  if ((MaxLen == 0) ||
> +      ((VariableName[MaxLen - 1] != 0) && (StrnLenS (VariableName, MaxLen)
> == MaxLen))) {
> +    //
> +    // Null-terminator is not found in the first VariableNameSize bytes of the
> input VariableName buffer.
> +    //
> +    return EFI_INVALID_PARAMETER;
> +  }
> +
>    Status = FindVariable (VariableName, VendorGuid, &Variable);
> 
>    if (Variable.CurrPtr == NULL || EFI_ERROR (Status)) {
> +    if (VariableName[0] != 0) {
> +      //
> +      // The input values of VariableName and VendorGuid are not a name
> and GUID of an existing variable.
> +      //
> +      Status = EFI_INVALID_PARAMETER;
> +    }
>      return Status;
>    }
> 
> --
> 2.7.0.windows.1