linux-kernel - Re: [PATCH] kernel: make /proc/kallsyms mode 400 to reduce ease of attacking

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Message-ID: <20101119201614.GB19329@1wt.eu>
Date:	Fri, 19 Nov 2010 21:16:14 +0100
From:	Willy Tarreau <w@....eu>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	david@...g.hm, Sarah Sharp <sarah.a.sharp@...ux.intel.com>,
	Marcus Meissner <meissner@...e.de>,
	linux-kernel@...r.kernel.org, tj@...nel.org,
	akpm@...ux-foundation.org, hpa@...or.com, mingo@...e.hu,
	alan@...rguk.ukuu.org.uk
Subject: Re: [PATCH] kernel: make /proc/kallsyms mode 400 to reduce ease of attacking

On Fri, Nov 19, 2010 at 12:04:47PM -0800, Linus Torvalds wrote:
> On Fri, Nov 19, 2010 at 11:58 AM,  <david@...g.hm> wrote:
> >
> > how far back do we need to maintain compatibility with userspace?
> >
> > Is this something that we can revisit in a few years and lock it down then?
> 
> The rule is basically "we never break user space".
> 
> But the "out" to that rule is that "if nobody notices, it's not
> broken". In a few years? Who knows?
> 
> So breaking user space is a bit like trees falling in the forest. If
> there's nobody around to see it, did it really break?

FWIW, I appreciate a lot that non-breaking rule. I have some testing
machines which boot from PXE or USB on a file-system with some old
tools and libc, that are both 2.4 and 2.6 compatible. Everything works
like a charm, the only point of care was to have both module-init-tools
and modutils (obviously) but even that integrates smoothly.

I know quite a lot of people who never replace user-space but only
kernels on their systems, so this non-breaking rule is much welcome !

Willy

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