From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <owner-linux-mm@kvack.org>
Received: from mail-lf0-f69.google.com (mail-lf0-f69.google.com [209.85.215.69])
	by kanga.kvack.org (Postfix) with ESMTP id E2AA96B04C9
	for <linux-mm@kvack.org>; Mon, 31 Jul 2017 16:17:23 -0400 (EDT)
Received: by mail-lf0-f69.google.com with SMTP id w199so64726559lff.2
        for <linux-mm@kvack.org>; Mon, 31 Jul 2017 13:17:23 -0700 (PDT)
Received: from mail-lf0-f68.google.com (mail-lf0-f68.google.com. [209.85.215.68])
        by mx.google.com with ESMTPS id i15si11570730ljd.25.2017.07.31.13.17.22
        for <linux-mm@kvack.org>
        (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128);
        Mon, 31 Jul 2017 13:17:22 -0700 (PDT)
Received: by mail-lf0-f68.google.com with SMTP id t128so15217040lff.3
        for <linux-mm@kvack.org>; Mon, 31 Jul 2017 13:17:22 -0700 (PDT)
Reply-To: alex.popov@linux.com
Subject: Re: [v3] mm: Add SLUB free list pointer obfuscation
References: <20170706002718.GA102852@beast>
 <cdd42a1b-ce15-df8c-6bd1-b0943275986f@linux.com>
 <CAGXu5jKRDhvqj0TU10W10hsdixN2P+hHzpYfSVvOFZy=hW72Mg@mail.gmail.com>
 <alpine.DEB.2.20.1707260906230.6341@nuc-kabylake>
 <CAGXu5jLkOjDKSZ48jOyh2voP17xXMeEnqzV_=8dGSvFmqdCZCA@mail.gmail.com>
 <alpine.DEB.2.20.1707261154140.9167@nuc-kabylake>
 <515333f5-1815-8591-503e-c0cf6941670e@linux.com>
 <alpine.DEB.2.20.1707271851390.17228@nuc-kabylake>
From: Alexander Popov <alex.popov@linux.com>
Message-ID: <4a6c0105-b084-aa87-6a2b-0650613df6ac@linux.com>
Date: Mon, 31 Jul 2017 23:17:19 +0300
MIME-Version: 1.0
In-Reply-To: <alpine.DEB.2.20.1707271851390.17228@nuc-kabylake>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: owner-linux-mm@kvack.org
List-ID: <linux-mm.kvack.org>
To: Christopher Lameter <cl@linux.com>, Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>, Pekka Enberg <penberg@kernel.org>, David Rientjes <rientjes@google.com>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>, Ingo Molnar <mingo@kernel.org>, Josh Triplett <josh@joshtriplett.org>, Andy Lutomirski <luto@kernel.org>, Nicolas Pitre <nicolas.pitre@linaro.org>, Tejun Heo <tj@kernel.org>, Daniel Mack <daniel@zonque.org>, Sebastian Andrzej Siewior <bigeasy@linutronix.de>, Sergey Senozhatsky <sergey.senozhatsky@gmail.com>, Helge Deller <deller@gmx.de>, Rik van Riel <riel@redhat.com>, Linux-MM <linux-mm@kvack.org>, Tycho Andersen <tycho@docker.com>, LKML <linux-kernel@vger.kernel.org>, "kernel-hardening@lists.openwall.com" <kernel-hardening@lists.openwall.com>

Hello Christopher and Kees,

Excuse me for the delayed reply.

On 28.07.2017 02:53, Christopher Lameter wrote:
> On Fri, 28 Jul 2017, Alexander Popov wrote:
> 
>> I don't really like ignoring double-free. I think, that:
>>   - it will hide dangerous bugs in the kernel,
>>   - it can make some kernel exploits more stable.
>> I would rather add BUG_ON to set_freepointer() behind SLAB_FREELIST_HARDENED. Is
>> it fine?
> 
> I think Kees already added some logging output.

Hm, I don't see anything like that in v4 of "SLUB free list pointer
obfuscation": https://patchwork.kernel.org/patch/9864165/

>> At the same time avoiding the consequences of some double-free errors is better
>> than not doing that. It may be considered as kernel "self-healing", I don't
>> know. I can prepare a second patch for do_slab_free(), as you described. Would
>> you like it?
> 
> The SLUB allocator is already self healing if you enable the option to do
> so on bootup (covers more than just the double free case). What you
> propose here is no different than that and just another way of having
> similar functionality. In the best case it would work the same way.

Ok, I see. Thanks.

Best regards,
Alexander

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>