Re: [edk2-devel] [PATCH v1 1/1] ShellPkg: acpiview: Validate ACPI table 'Length' field

["Gao, Zhichao" <zhichao.gao@intel.com>]

> -----Original Message-----
> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Krzysztof
> Koch
> Sent: Friday, January 31, 2020 12:20 AM
> To: devel@edk2.groups.io
> Cc: Ni, Ray <ray.ni@intel.com>; Gao, Zhichao <zhichao.gao@intel.com>;
> Matteo.Carlini@arm.com; sami.mujawar@arm.com; nd@arm.com
> Subject: [edk2-devel] [PATCH v1 1/1] ShellPkg: acpiview: Validate ACPI table
> 'Length' field
> 
> Check if the ACPI table length, as reported in the ACPI table header, is big
> enough to fit at least the header itself.
> 
> If not, report an error to the user and stop parsing the table in order to prevent
> buffer overruns.
> 
> Signed-off-by: Krzysztof Koch <krzysztof.koch@arm.com>
> ---
> 
> Changes can be seet at:
> https://github.com/KrzysztofKoch1/edk2/pull/new/650_add_checks_process_a
> cpi_table_v1
> 
> Notes:
>     v1:
>     - Validate ACPI table length [Krzysztof]
> 
>  ShellPkg/Library/UefiShellAcpiViewCommandLib/AcpiTableParser.c | 22
> +++++++++++++++++++-
>  1 file changed, 21 insertions(+), 1 deletion(-)
> 
> diff --git a/ShellPkg/Library/UefiShellAcpiViewCommandLib/AcpiTableParser.c
> b/ShellPkg/Library/UefiShellAcpiViewCommandLib/AcpiTableParser.c
> index
> d5500bcb2b4a55c7a69f45444aa49d36d2c1694f..0c93bca4fc0f7d2f105a765425
> 8e00f714fc1519 100644
> --- a/ShellPkg/Library/UefiShellAcpiViewCommandLib/AcpiTableParser.c
> +++ b/ShellPkg/Library/UefiShellAcpiViewCommandLib/AcpiTableParser.c
> @@ -1,7 +1,7 @@
>  /** @file
>    ACPI table parser
> 
> -  Copyright (c) 2016 - 2019, ARM Limited. All rights reserved.
> +  Copyright (c) 2016 - 2020, ARM Limited. All rights reserved.
>    SPDX-License-Identifier: BSD-2-Clause-Patent  **/
> 
> @@ -176,6 +176,7 @@ ProcessAcpiTable (
>    CONST UINT32* AcpiTableSignature;
>    CONST UINT32* AcpiTableLength;
>    CONST UINT8*  AcpiTableRevision;
> +  CONST UINT8*  SignaturePtr;
>    PARSE_ACPI_TABLE_PROC ParserProc;
> 
>    ParseAcpiHeader (
> @@ -193,6 +194,25 @@ ProcessAcpiTable (
> 
>    if (Trace) {
>      DumpRaw (Ptr, *AcpiTableLength);
> +
> +    /*
> +      Do not process the ACPI table any further if the table length read
> +      is invalid. The ACPI table should at least contain the table header.
> +    */

The internal comment is suggested to use C++ style, refer to CSS 2.1 section 6.5.2.1:
For internal code comments, use C++ style (//) comment lines.

Thanks,
Zhichao

> +    if (*AcpiTableLength < sizeof (EFI_ACPI_DESCRIPTION_HEADER)) {
> +      SignaturePtr = (CONST UINT8*)AcpiTableSignature;
> +      IncrementErrorCount ();
> +      Print (
> +        L"ERROR: Invalid %c%c%c%c table length. Length = %d\n",
> +        SignaturePtr[0],
> +        SignaturePtr[1],
> +        SignaturePtr[2],
> +        SignaturePtr[3],
> +        *AcpiTableLength
> +        );
> +      return;
> +    }
> +
>      if (GetConsistencyChecking ()) {
>        VerifyChecksum (TRUE, Ptr, *AcpiTableLength);
>      }
> --
> 'Guid(CE165669-3EF3-493F-B85D-6190EE5B9759)'
> 
> 
> 
>