Openwall GNU/*/Linux - a small security-enhanced Linux distro for servers
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Date: Fri, 4 Oct 2013 10:05:38 +0100
From: Djalal Harouni <tixxdz@...ndz.org>
To: Ingo Molnar <mingo@...nel.org>
Cc: Kees Cook <keescook@...omium.org>,
	Andy Lutomirski <luto@...capital.net>,
	"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>,
	"Serge E. Hallyn" <serge.hallyn@...ntu.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	David Rientjes <rientjes@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>,
	"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>,
	Djalal Harouni <tixxdz@...il.com>
Subject: Re: [PATCH v2 0/9] procfs: protect /proc/<pid>/* files with
 file->f_cred

On Thu, Oct 03, 2013 at 08:12:44AM +0200, Ingo Molnar wrote:
> So please first get consensus on this fundamental design question before 
> spreading your solution to more areas.
Check file_ns_capable() added in commit 935d8aabd4331 by Linus
Add file_ns_capable() helper function for open-time capability checking

commit 6708075f104c3c9b0 by Eric,
userns: Don't let unprivileged users trick privileged users into setting
the id_map

So they add file_ns_capable() to inspect file->f_cred during ->write()

The difference between the function I've added proc_allow_access() and
file_ns_capable() is that proc_allow_access() will check if it's
absolutely the same user, otherwise fallback to security_capable() which
is the heart of file_ns_capable()

So it's already been done and proposed! this is an easy solution to
detect if current's cred have changed.


> Thanks,
> 
> 	Ingo

-- 
Djalal Harouni
http://opendz.org

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