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

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Message-ID: <20101120110546.GA2940@amd.home.annexia.org>
Date:	Sat, 20 Nov 2010 11:05:46 +0000
From:	"Richard W.M. Jones" <rjones@...hat.com>
To:	Marcus Meissner <meissner@...e.de>
Cc:	torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
	tj@...nel.org, akpm@...l.org, hpa@...or.com, mingo@...e.hu,
	w@....eu, alan@...rguk.ukuu.org.uk
Subject: Re: [PATCH] kernel: make /proc/kallsyms mode 400 to reduce ease of
 attacking

Sorry for being late to join this thread.

I thought I'd also mention that if you can insert a small amount of
shell code into the kernel, it's trivial to search kernel memory for
the symbol table and derive anything else you want from that.

I wrote some proof of concept code to do this a few years ago[1].  I'm
pretty sure you could compress this down to a few bytes of assembler.

(Plus I don't think that removing pointers is a good idea anyway -- it
just breaks userspace tools, and any real world system is going to be
running a well-known kernel that can be downloaded from some mirror
somewhere)

Rich.

[1] It's a poor example, but in here is code that searched for ksyms
and kallsyms in 32 bit i386 kernels (files virt_mem_ksyms.ml and
virt_mem_kallsyms.ml).
http://git.annexia.org/?p=virt-mem.git;a=tree;f=lib;hb=HEAD

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