kernel-hardening - Re: [PATCH v2 2/9] procfs: add proc_allow_access() to check if file's opener may access task

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Date: Mon, 7 Oct 2013 14:41:33 -0700
From: Andy Lutomirski <luto@...capital.net>
To: Djalal Harouni <tixxdz@...ndz.org>
Cc: "Eric W. Biederman" <ebiederm@...ssion.com>, Kees Cook <keescook@...omium.org>, 
	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>, 
	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 2/9] procfs: add proc_allow_access() to check if file's
 opener may access task

On Sat, Oct 5, 2013 at 6:23 AM, Djalal Harouni <tixxdz@...ndz.org> wrote:
> On Fri, Oct 04, 2013 at 03:17:08PM -0700, Andy Lutomirski wrote:
>>
>> Exactly.  Hence the NAK.
> But Having two LSM Hooks there is really not practical!

It'd doable *if* it turns out that it's the right solution.

But revoke seems much more likely to be simple, comprehensible, and
obviously correct to me.

--Andy

>
> Note to mention some of these redundancy checks...
>
>> >
>> > Is there some mechanism to check what you describe?
>> >
>>
>> No.  You could try to add one, but getting it to be compatible with
>> YAMA might be really messy.
> LSM is limitted in this situation, and it can't work with YAMA, or
> perhaps YAMA will just return -EPERM
>
> So this LSM protections are currently vulnerable too!
>
>
>> Or you could see if destroying and recreating all the inodes on exec
>> or some other revoke-like approach would work.
>>
>> --Andy
>
> --
> Djalal Harouni
> http://opendz.org



-- 
Andy Lutomirski
AMA Capital Management, LLC

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