Re: [PATCH] Fix edit on screens with more than 200 columns

["Witt, Sebastian" <sebastian.witt@siemens.com>]

Only performance. But I haven't measured if there is a big difference between static buffer and AllocateZeroPool. I wouldn't use a fixed value. There may be a display device with more than 400 columns. Otherwise one can always allocate the [LastCol + 1] buffer.

-----Original Message-----
From: Carsey, Jaben [mailto:jaben.carsey@intel.com] 
Sent: Dienstag, 24. Januar 2017 17:27
To: Witt, Sebastian (DF FA AS DH KHE 1); edk2-devel@lists.01.org
Cc: Carsey, Jaben
Subject: RE: [PATCH] Fix edit on screens with more than 200 columns

Is there a reason to not just always start with allocating the 400 and then we don't need to complicate the end to conditionally free the buffer?

> -----Original Message-----
> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of 
> Witt, Sebastian
> Sent: Tuesday, January 24, 2017 5:14 AM
> To: edk2-devel@lists.01.org
> Subject: [edk2] [PATCH] Fix edit on screens with more than 200 columns
> Importance: High
> 
> If the shell edit command is used on a screen with more than
> 200 columns, we get a buffer overflow. This increases the default 
> buffer size to
> 400 columns and allocates a pool when this is not enough.
> 
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Sebastian Witt <sebastian.witt@siemens.com>
> 
> ---
>  .../UefiShellDebug1CommandsLib.c                          | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git
> a/ShellPkg/Library/UefiShellDebug1CommandsLib/UefiShellDebug1CommandsL
> i
> b.c
> b/ShellPkg/Library/UefiShellDebug1CommandsLib/UefiShellDebug1CommandsL
> i
> b.c
> index 6ebf002..d81dd01 100644
> ---
> a/ShellPkg/Library/UefiShellDebug1CommandsLib/UefiShellDebug1CommandsL
> i
> b.c
> +++
> b/ShellPkg/Library/UefiShellDebug1CommandsLib/UefiShellDebug1Command
> +++ sLib.c
> @@ -302,12 +302,21 @@ EditorClearLine (
>    IN UINTN LastRow
>    )
>  {
> -  CHAR16 Line[200];
> +  CHAR16 Buffer[400];
> +  CHAR16 *Line = Buffer;
> 
>    if (Row == 0) {
>      Row = 1;
>    }
> 
> +  // If there are more columns than our buffer can contain, allocate 
> + new buffer  if (LastCol >= (sizeof (Buffer) / sizeof (CHAR16))) {
> +    Line = AllocateZeroPool (LastCol*(sizeof(CHAR16) + 1));
> +    if (Line == NULL) {
> +      return;
> +    }
> +  }
> +
>    //
>    // prepare a blank line
>    //
> @@ -326,6 +335,10 @@ EditorClearLine (
>    // print out the blank line
>    //
>    ShellPrintEx (0, ((INT32)Row) - 1, Line);
> +
> +  // Free if allocated
> +  if (Line != Buffer)
> +    FreePool (Line);
>  }
> 
>  /**
> --
> 2.1.4
> 
> With best regards,
> Sebastian Witt
> 
> Siemens AG
> Digital Factory Division
> Factory Automation
> Automation Products and Systems
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> Tel.: +49 721 595-5326
> mailto:sebastian.witt@siemens.com
> 
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> 
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