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Message-ID: <20171107203933.GV18478@eros>
Date: Wed, 8 Nov 2017 07:39:33 +1100
From: "Tobin C. Harding" <me@...in.cc>
To: Petr Mladek <pmladek@...e.com>
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, Nov 07, 2017 at 04:51:29PM +0100, Petr Mladek wrote:
> 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.
Awesome. Thank you very much. All comments will be addressed for the
next spin.
thanks,
Tobin.
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