netdev - Re: [kernel-hardening] [PATCH v4] scripts: add leaking

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Message-ID: <20171112211823.GJ19752@eros>
Date:   Mon, 13 Nov 2017 08:18:23 +1100
From:   "Tobin C. Harding" <me@...in.cc>
To:     Frank Rowand <frowand.list@...il.com>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        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>,
        Petr Mladek <pmladek@...e.com>, 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: [kernel-hardening] [PATCH v4] scripts: add leaking_addresses.pl

On Sun, Nov 12, 2017 at 10:02:55AM -0800, Frank Rowand wrote:
> Hi Michael,
> 
> On 11/12/17 03:49, Michael Ellerman wrote:
> > Hi Frank,
> > 
> > Frank Rowand <frowand.list@...il.com> writes:
> >> Hi Michael, Tobin,
> >>
> >> On 11/08/17 04:10, Michael Ellerman wrote:
> >>> "Tobin C. Harding" <me@...in.cc> writes:
> >>>> 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.
> >>>
> >>> That doesn't work super well on other architectures :D
> >>>
> >>> I don't speak perl but presumably you can check the arch somehow and
> >>> customise the regex?
> >>>
> >>> ...
> >>>> +# Return _all_ non false positive addresses from $line.
> >>>> +sub extract_addresses
> >>>> +{
> >>>> +        my ($line) = @_;
> >>>> +        my $address = '\b(0x)?ffff[[:xdigit:]]{12}\b';
> >>>
> >>> On 64-bit powerpc (ppc64/ppc64le) we'd want:
> >>>
> >>> +        my $address = '\b(0x)?[89abcdef]00[[:xdigit:]]{13}\b';
> >>>
> >>>
> >>>> +# Do not parse these files (absolute path).
> >>>> +my @skip_parse_files_abs = ('/proc/kmsg',
> >>>> +			    '/proc/kcore',
> >>>> +			    '/proc/fs/ext4/sdb1/mb_groups',
> >>>> +			    '/proc/1/fd/3',
> >>>> +			    '/sys/kernel/debug/tracing/trace_pipe',
> >>>> +			    '/sys/kernel/security/apparmor/revision');
> >>>
> >>> Can you add:
> >>>
> >>>   /sys/firmware/devicetree
> >>>
> >>> and/or /proc/device-tree (which is a symlink to the above).
> >>
> >> /proc/device-tree is a symlink to /sys/firmware/devicetree/base
> > 
> > Oh yep, forgot about the base part.
> > 
> >> /sys/firmware contains
> >>    fdt              -- the flattened device tree that was passed to the
> >>                        kernel on boot
> >>    devicetree/base/ -- the data that is currently in the live device tree.
> >>                        This live device tree is represented as directories
> >>                        and files beneath base/
> >>
> >> The information in fdt is directly available in the kernel source tree
> > 
> > On ARM that might be true, but not on powerpc.

Looks like we should be considering architecture specific lists for
files/directories to skip.

thanks,
Tobin.