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

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Date:   Sun, 12 Nov 2017 10:02:55 -0800
From:   Frank Rowand <frowand.list@...il.com>
To:     Michael Ellerman <mpe@...erman.id.au>,
        "Tobin C. Harding" <me@...in.cc>,
        kernel-hardening@...ts.openwall.com
Cc:     "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

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.
> 
> Remember FDT comes from DT which comes from OF - in which case the
> information is definitely not in the kernel source! :)
> 
> On our bare metal machines the device tree comes from skiboot
> (firmware), with some of the content provided by hostboot (other
> firmware), both of which are open source, so in theory most of the
> information is available in *some* source tree. But there's still
> information about runtime allocations etc. that is not available in the
> source anywhere.

Thanks for the additional information. 

Can you explain a little bit what "runtime allocations" are?  Are you
referring to the memory reservation block, the memory node(s) and the
chosen node?  Or other information?