From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S932896AbcIAQaw (ORCPT <rfc822;w@1wt.eu>);
        Thu, 1 Sep 2016 12:30:52 -0400
Received: from mail-oi0-f48.google.com ([209.85.218.48]:33447 "EHLO
        mail-oi0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1754997AbcIAQau (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Thu, 1 Sep 2016 12:30:50 -0400
MIME-Version: 1.0
In-Reply-To: <20160901130920.e7ac4jff6swqqbfc@treble>
References: <cover.1472057064.git.jpoimboe@redhat.com> <9fbe0db05bacf66d337c162edbf61450d0cff1e2.1472057064.git.jpoimboe@redhat.com>
 <CA+55aFyaLgbocKa4Ec1J4Z12p4-N66MQGOj-HLaxP8RSW8NOrw@mail.gmail.com>
 <20160824182220.GB10153@twins.programming.kicks-ass.net> <CA+55aFzAqoxqzN3eG96qAAMF-qsHe=MWOqi1wK+7Vpq9=-Un1Q@mail.gmail.com>
 <20160831165303.tvcudt7wkpechuqt@treble> <CA+55aFwpLR-z1ywSpjSc5XQp4WZFAVV989JDwgoieJMuSPWvRw@mail.gmail.com>
 <20160901130920.e7ac4jff6swqqbfc@treble>
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Thu, 1 Sep 2016 09:30:48 -0700
X-Google-Sender-Auth: aOs8VsDg9upJSIZqAMnrdu2uLjE
Message-ID: <CA+55aFwipyNLDGqosAMZqvibTUCjrNKZ9shhdMwgcLw2CzdLwg@mail.gmail.com>
Subject: Re: [PATCH 3/6] x86/dumpstack: make printk_stack_address() more
 generally useful
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@kernel.org>,
        "H . Peter Anvin" <hpa@zytor.com>,
        "the arch/x86 maintainers" <x86@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Andy Lutomirski <luto@amacapital.net>,
        Steven Rostedt <rostedt@goodmis.org>, Brian Gerst <brgerst@gmail.com>,
        Kees Cook <keescook@chromium.org>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Byungchul Park <byungchul.park@lge.com>,
        Nilay Vaish <nilayvaish@gmail.com>
Content-Type: text/plain; charset=UTF-8
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Thu, Sep 1, 2016 at 6:09 AM, Josh Poimboeuf <jpoimboe@redhat.com> wrote:
>
> I'm wonder if it might be useful to encode the addresses somehow; they
> could conceivably be used to debug use-after-free issues.  Or we could
> just remove them.

I suspect we should just remove them. I'm sure they are useful in
theory, but I suspect they were more useful back when the whole "free
init memory" was originally done.

These days, if we have a use-after-free, I suspect the init-mem
situation is the easiest situation by far. Compared to all the dynamic
allocations which are much more likely to show it anyway. So having
debug output for that case is likely not all that productive.

              Linus