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Date: Sat, 28 Sep 2013 15:35:23 +0100
From: Djalal Harouni <tixxdz@...ndz.org>
To: Kees Cook <keescook@...omium.org>
Cc: "Eric W. Biederman" <ebiederm@...ssion.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	"Serge E. Hallyn" <serge.hallyn@...ntu.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>,
	tixxdz@...il.com
Subject: Re: [PATCH 06/12] procfs: make /proc/*/stack 0400

On Thu, Sep 26, 2013 at 03:43:24PM -0500, Kees Cook wrote:
> On Wed, Sep 25, 2013 at 3:14 PM, Djalal Harouni <tixxdz@...ndz.org> wrote:
> > The /proc/*/stack contains sensitive information and currently its mode
> > is 0444. Change this to 0400 so the VFS will be able to block
> > unprivileged processes to get file descriptors on arbitrary privileged
> > /proc/*/stack files.
> >
> > The /proc/*/stack is a /procfs ONE file that shares the same ->open()
> > file operation with other ONE files. Doing a ptrace_may_access() check
> > during open() might break userspace from accessing other ONE files
> > like /proc/*/stat and /proc/*/statm.
> >
> > Therfore make it 0400 for now, and improve its check during ->read()
> > in the next following patch.
> >
> > Cc: Kees Cook <keescook@...omium.org>
> > Cc: Eric W. Biederman <ebiederm@...ssion.com>
> > Signed-off-by: Djalal Harouni <tixxdz@...ndz.org>
> 
> While the rest of the series is being discussed, I think it would be
> nice to at least get this into the tree. Fixing this reduces which
> processes are exposed to ASLR leaks. The rest of the series closes the
> remaining holes.
> 
> I would if it would be valuable adding a test for the identified leak
> conditions to some test suite? LTP perhaps?
I'm not familiar with LTP, but I guess a small program that perform I/O
redirection and execve a suid-exec will do it?

I'll try to add code comment in fs/proc/base.c


> -Kees
> 
> -- 
> Kees Cook
> Chrome OS Security

-- 
Djalal Harouni
http://opendz.org

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