Message-ID: <4C72D1E1.1040709@goop.org>
Date: Mon, 23 Aug 2010 12:54:09 -0700
From: Jeremy Fitzhardinge <jeremy@goop.org>
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To: Peter Zijlstra <peterz@infradead.org>
CC: Linus Torvalds <torvalds@linux-foundation.org>,
        Ian Jackson <ijackson@chiark.greenend.org.uk>,
        Greg KH <gregkh@suse.de>, Ian Campbell <ijc@hellion.org.uk>,
        linux-kernel@vger.kernel.org, stable@kernel.org,
        stable-review@kernel.org, akpm@linux-foundation.org,
        alan@lxorguk.ukuu.org.uk
Subject: Re: [RFC] mlock/stack guard interaction fixup
References: <AANLkTimuP9cFvd4pfqy6=vixSMdagrSEv1-VLNAEuWgr@mail.gmail.com>	 <1282391770.29609.1223.camel@localhost.localdomain>	 <AANLkTimYnfewBCDNYXZHxbcX=TRE__Cu07_FFK_kAK2h@mail.gmail.com>	 <1282460275.11348.865.camel@localhost.localdomain>	 <1282462386.11348.871.camel@localhost.localdomain>	 <1282470917.11348.891.camel@localhost.localdomain>	 <20100822172548.GB8957@suse.de>	 <AANLkTi=wWcAg8MdWy4O-0au3m6mH+9xWDOKVCJ_x5G_v@mail.gmail.com>	 <19570.38608.79434.179797@chiark.greenend.org.uk>	 <1282580751.2605.1997.camel@laptop>	 <19570.44367.719276.128881@chiark.greenend.org.uk>	 <AANLkTi=+O8wKZV6XT5wGJbfZdgC9kxTxvtEZMD+M+pZn@mail.gmail.com>	 <4C72C2E9.3070408@goop.org> <1282590457.2605.2200.camel@laptop>	 <4C72CAA7.5070202@goop.org> <1282591592.2605.2221.camel@laptop>
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 On 08/23/2010 12:26 PM, Peter Zijlstra wrote:
> On Mon, 2010-08-23 at 12:23 -0700, Jeremy Fitzhardinge wrote:
>> On 08/23/2010 12:07 PM, Peter Zijlstra wrote:
>>> mlock() simply avoids major faults, nothing more.
>>>
>>> I think both page migration and page-out for shared pages where some
>>> maps are !mlocked can cause unmaps and thus minor faults.
>>>
>>> mlock and dirty do not interact, they will still be cleaned/written out
>>> as normal.
>> So mlock is useless for preventing secret stuff from being written to disk.
> Well, if you put your sekrit in a file map, sure.
>
> Use a mmap(MAP_ANONYMOUS|MAP_LOCK) and madvise(MADV_DONTFORK) for your
> sekrits.

Won't dirty anonymous pages also get written to swap?

    J
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