linux-kernel - Re: [PATCH 0/5] add printk specifier %px, unique identifier

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Message-ID: <CA+55aFx+bMOT-DDp3EYuio0aJDGzWa3PzQxVbM3Rz+GdZKaaFQ@mail.gmail.com>
Date:   Tue, 28 Nov 2017 09:33:19 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     "Tobin C. Harding" <me@...in.cc>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        "Theodore Ts'o" <tytso@....edu>, Kees Cook <keescook@...omium.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Tycho Andersen <tycho@...ho.ws>,
        "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>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        KVM list <kvm@...r.kernel.org>,
        "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH 0/5] add printk specifier %px, unique identifier

On Mon, Nov 27, 2017 at 10:26 PM, Eric W. Biederman
<ebiederm@...ssion.com> wrote:
>>
>> Oh well, I just did /proc/<pid>/stack by making it just print 0
>> unconditionally rather than the hex number.
>
> Patch?

Oh, apparently I never pushed out yesterday.

The patch literally just affects the (useless) hex number. So:

    cat /proc/self/stack

now prints out

    [<0>] proc_pid_stack+0xaa/0x100
    [<0>] proc_single_show+0x48/0x80
    [<0>] seq_read+0xd2/0x410
    ...

instead of putting some randomized kernel address there.

I considered getting rid of the whole "[<>]" thing, but that's where
"maybe there are tools that parse this" came in.

I doubt there are any, though. If proc-ps doesn't look at this, I
don't know what could. But the format change might as well be a
separate thing if somebody cares deeply.

                     Linus