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

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Message-ID: <CAPDLWs-yd13yh4NKpB4msAxcG6BeXMSohfpU_Vv2RJFc5ApddA@mail.gmail.com>
Date:   Thu, 9 Nov 2017 10:24:32 +0530
From:   Kaiwan N Billimoria <kaiwan.billimoria@...il.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Laura Abbott <labbott@...hat.com>,
        "Tobin C. Harding" <me@...in.cc>,
        "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        "Theodore Ts'o" <tytso@....edu>, 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 Mailing List <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 Thu, Nov 9, 2017 at 10:13 AM, Kaiwan N Billimoria
<kaiwan.billimoria@...il.com> wrote:
>> But I don't know if there is anything else than the profiling code
>> that _really_ wants access to /proc/kallsyms in user space as a
>> regular user.
>

Front-ends to ftrace, like trace-cmd?
[from the trace-cmd git repo (Steve Rostedt, pl stand up, pl stand up :-)
Documentation/trace-cmd-restore.1.txt :
...
*-k* kallsyms::
    Used with *-c*, it overrides where to read the kallsyms file from.
    By default, /proc/kallsyms is used. *-k* will override the file to
    read the kallsyms from. This can be useful if the trace.dat file
    to create is from another machine. Just copy the /proc/kallsyms
    file locally, and use *-k* to point to that file.
...
]

> Am unsure about this, but kprobes? (/jprobes/kretprobes), and by
> extension, wrappers over this infra (like SystemTap)?
> I (hazily) recollect a script I once wrote (years back though) that
> collects kernel virtual addresses off of kallsyms for the purpose of
> passing them to a 'helper' kernel module that uses kprobes. I realize
> that 'modern' kprobes exposes APIs that just require the symbolic name
> & that they're anyway at kernel privilege... but the point is, a
> usermode script was picking up and passing the kernel addresses.
>
> Also, what about kernel addresses exposed via System.map?
> Oh, just checked, it's root rw only.. pl ignore.