[PATCH] GcovData.cc: Fix out-of-bounds access errors

[Ryan Long]

Would you need to check if length < sizeof(gcov_preamble) since length is assigned that value? 

-----Original Message-----
From: Gedare Bloom <gedare at rtems.org> 
Sent: Wednesday, August 11, 2021 11:13 AM
To: Ryan Long <ryan.long at oarcorp.com>
Cc: devel at rtems.org
Subject: Re: [PATCH] GcovData.cc: Fix out-of-bounds access errors

On Wed, Aug 11, 2021 at 8:06 AM Ryan Long <ryan.long at oarcorp.com> wrote:
>
> Adjusted number of bytes to be read
>
> CID 1506208: Out-of-bounds access
> CID 1506209: Out-of-bounds access
>
> Closes #4485
> ---
>  tester/covoar/GcovData.cc | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/tester/covoar/GcovData.cc b/tester/covoar/GcovData.cc 
> index 02e7489..da0cc2a 100644
> --- a/tester/covoar/GcovData.cc
> +++ b/tester/covoar/GcovData.cc
> @@ -129,7 +129,7 @@ namespace Gcov {
>      preamble.timestamp = gcnoPreamble.timestamp;
>
>      //Write preamble
> -    gcdaFile.write( (char *) &preamble , 4 * sizeof( preamble ) );
> +    gcdaFile.write( (char *) &preamble , sizeof( preamble ) );
>      if ( gcdaFile.fail() ) {
>        std::cerr << "Error while writing gcda preamble to a file "
>                  << gcdaFileName << std::endl; @@ -402,8 +402,8 @@ 
> namespace Gcov {
>      int length;
>
>      length = sizeof( gcov_preamble );
> -    gcovFile.read( (char *) &preamble, 4 * sizeof( gcov_preamble ) );
> -    if ( gcovFile.gcount() != 4 * sizeof( gcov_preamble ) ) {
> +    gcovFile.read( (char *) &preamble, length );
Does something ensure that sizeof(preamble) < length?

regardless, the patch looks like an improvement, go ahead.

> +    if ( gcovFile.gcount() != length ) {
>        std::cerr << "Error while reading file preamble" << std::endl;
>        return -1;
>      }
> --
> 1.8.3.1
>
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