linux-kernel - Re: [PATCH] leaking_addresses: add support for 32-bit kernel addresses

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Message-ID: <20171204045522.GE27780@eros>
Date:   Mon, 4 Dec 2017 15:55:22 +1100
From:   "Tobin C. Harding" <me@...in.cc>
To:     kaiwan.billimoria@...il.com
Cc:     Alexander Kapshuk <alexander.kapshuk@...il.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH] leaking_addresses: add support for 32-bit kernel
 addresses

On Mon, Dec 04, 2017 at 10:11:21AM +0530, kaiwan.billimoria@...il.com wrote:
> On Mon, 2017-12-04 at 11:11 +1100, Tobin C. Harding wrote:
> > On Fri, Dec 01, 2017 at 06:39:07PM +0530, kaiwan.billimoria@...il.com wrote:
> 
> > > @@ -267,7 +266,7 @@ sub is_false_positive
> > >  sub is_false_positive_ix86_32
> > >  {
> > >  	my ($match) = @_;
> > > -	state $page_offset = get_page_offset(); # only gets called once
> > > +	state $page_offset = eval get_page_offset(); # only gets called once
> > 
> > Why do you use 'eval' here?
> > 
> Without the eval:
> i.e.
>   state $page_offset = get_page_offset(); # only gets called once
> 
> $ ./leaking_addresses.pl  |head -200
> Argument "0x80000000" isn't numeric in numeric lt (<) at ./leaking_addresses.pl line 277.
> ...
> 
> With the 'eval', no warning, it's fine.

Why not use hex()?

> Additional Comments:
> 
> a) When running in debug mode, print the arch we're currently running on
> b) Also, while checking, I found another bug; requires the fix below (strip the filename of LF).
> 
> Patch follows:
> 
> ---
> diff --git a/scripts/leaking_addresses.pl b/scripts/leaking_addresses.pl
> index 3a8691a642c8..9906dcf8b807 100755
> --- a/scripts/leaking_addresses.pl
> +++ b/scripts/leaking_addresses.pl
> @@ -158,8 +158,8 @@ if (!$input_raw and ($squash_by_path or $squash_by_filename)) {
>         exit(128);
>  }
>  
> +show_detected_architecture() if $debug;
>  if (!is_supported_architecture()) {
> -       show_detected_architecture() if $debug;
>         printf "\nScript does not support your architecture, sorry.\n";
>         printf "\nCurrently we support: \n\n";
>         foreach(@SUPPORTED_ARCHITECTURES) {
> @@ -313,6 +313,7 @@ sub get_page_offset
>         }
>  
>         foreach my $config_file (@config_files) {
> +               $config_file =~ s/\R*//g;

Is there some reason you don't use chomp()?

thanks,
Tobin.