linux-kernel - Re: [PATCH v4] scripts: add leaking

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Message-ID: <20171107155129.GE2652@pathway.suse.cz>
Date:   Tue, 7 Nov 2017 16:51:29 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     "Tobin C. Harding" <me@...in.cc>
Cc:     kernel-hardening@...ts.openwall.com,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Theodore Ts'o <tytso@....edu>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Tycho Andersen <tycho@...ker.com>,
        "Roberts, William C" <william.c.roberts@...el.com>,
        Tejun Heo <tj@...nel.org>,
        Jordan Glover <Golden_Miller83@...tonmail.ch>,
        Greg KH <gregkh@...uxfoundation.org>,
        Joe Perches <joe@...ches.com>,
        Ian Campbell <ijc@...lion.org.uk>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <wilal.deacon@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Chris Fries <cfries@...gle.com>,
        Dave Weinstein <olorin@...gle.com>,
        Daniel Micay <danielmicay@...il.com>,
        Djalal Harouni <tixxdz@...il.com>,
        linux-kernel@...r.kernel.org,
        Network Development <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>
Subject: Re: [PATCH v4] scripts: add leaking_addresses.pl

On Tue 2017-11-07 21:32:11, Tobin C. Harding wrote:
> Currently we are leaking addresses from the kernel to user space. This
> script is an attempt to find some of those leakages. Script parses
> `dmesg` output and /proc and /sys files for hex strings that look like
> kernel addresses.
> 
> Only works for 64 bit kernels, the reason being that kernel addresses
> on 64 bit kernels have 'ffff' as the leading bit pattern making greping
> possible. On 32 kernels we don't have this luxury.
> 
> Scripts is _slightly_ smarter than a straight grep, we check for false
> positives (all 0's or all 1's, and vsyscall start/finish addresses).
> 
> Output is saved to file to expedite repeated formatting/viewing of
> output.
> 
> diff --git a/scripts/leaking_addresses.pl b/scripts/leaking_addresses.pl
> new file mode 100755
> index 000000000000..282c0cc2bdea
> --- /dev/null
> +++ b/scripts/leaking_addresses.pl
> +sub help
> +{
> +	my ($exitcode) = @_;
> +
> +	print << "EOM";
> +Usage: $P COMMAND [OPTIONS]
> +Version: $V
> +
> +Commands:
> +
> +	scan	Scan the kernel (savesg raw results to file and runs `format`).
> +	format	Parse results file and format output.
> +
> +Options:
> +	-o, --output=<path>	 Accepts absolute or relative filename or directory name.

IMHO, this is pretty non-standard. I would support only -o file. Then you do
not need to solve problems with replacing an existing file. The user
would know exactly what file will be generated.


> +	    --suppress-dmesg	 Don't show dmesg results.

The apostrophe breaks highlighting of the rest of the code ;-)


> +	    --squash-by-path	 Show one result per unique path.
> +	    --raw	 	 Show raw results.
> +	    --send-report	 Submit raw results for someone else to worry about.
> +	-d, --debug              Display debugging output.
> +	-h, --help, --version    Display this help and exit.
> +
> +Scans the running (64 bit) kernel for potential leaking addresses.
> +}

This bracket should not be here. The help text is limited
by "EOM" below.


> +
> +EOM
> +	exit($exitcode);
> +}

[...]

> +sub cache_path
> +{
> +        my ($paths, $line) = @_;
> +
> +        my $index = index($line, ':');

There are paths with the double dot, for example:
/sys/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.6/2-1.6:1.0/input/input4/uevent
Then the file name is wrongly detected, in my example as "pci0000"

It seems that searching for ": " sub-string works rather well.
I mean using:

	my $index = index($line, ': ');

> +        my $path = substr($line, 0, $index);
> +
> +        if (!$paths->{$path}) {
> +                $paths->{$path} = ();
> +        }
> +        push @{$paths->{$path}}, $line;

It would make sense to use the same trick from cache_filename
and remove path from the cached text. I mean:

	$index += 2;            # skip ': '
	push @{$paths->{$path}}, substr($line, $index);

> +}
> +
> +sub cache_filename
> +{
> +        my ($files, $line) = @_;
> +
> +        my $index = index($line, ':');

Same problem with the double dot in the path name.
The following helped me:

	my $index = index($line, ': ');

> +        my $path = substr($line, 0, $index);
> +        my $filename = basename($path);
> +        if (!$files->{$filename}) {
> +                $files->{$filename} = ();
> +        }
> +        $index += 2;            # skip ': '
> +        push @{$files->{$filename}}, substr($line, $index);
> +}

This is what caught my eye when trying the script.

Best Regards,
Petr