From mboxrd@z Thu Jan  1 00:00:00 1970
Reply-To: kernel-hardening@lists.openwall.com
Sender: Vasiliy Kulikov <segooon@gmail.com>
Date: Mon, 22 Aug 2011 13:45:58 +0400
From: Vasiliy Kulikov <segoon@openwall.com>
Message-ID: <20110822094558.GA2620@albatros>
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In-Reply-To: <20110822093819.GA13665@openwall.com>
Subject: Re: [kernel-hardening] kmalloc() nofail allocations
To: kernel-hardening@lists.openwall.com
List-ID: <kernel-hardening.lists.openwall.com>

Solar,

On Mon, Aug 22, 2011 at 13:38 +0400, Solar Designer wrote:
> On Mon, Aug 22, 2011 at 01:24:29PM +0400, Vasiliy Kulikov wrote:
> > Major problem with the idea in general:
> ...
> > Unlikely, but fully possible case - we want some memory and the OOM killer
> > kills us for our wish.
> 
> How/why is this a major problem with the idea in general?  I am probably
> missing something.

Initially I wanted to "wrap" kmalloc calls, which cannot fail in any
case.  This would not change any mm code, but the caller (its
expectation).

Now I see that it's impossible without any mm code changes.  It needs at
least __GFP_NOFAIL flag addition, which is explicitly marked as "no new
uses".  Such kmalloc_nofail() wouldn't differ much from kmalloc(size,
flags | __GFP_NOFAIL).


Thanks,

-- 
Vasiliy