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Message-ID: <86802c440804151900t3357eb52w4cf2339b38ce2c17@mail.gmail.com>
Date: Tue, 15 Apr 2008 19:00:18 -0700
From: "Yinghai Lu" <yhlu.kernel@gmail.com>
To: "Ingo Molnar" <mingo@elte.hu>
Subject: Re: [patch] mm: sparsemem memory_present() memory corruption fix
Cc: "Christoph Lameter" <clameter@sgi.com>,
       "Linus Torvalds" <torvalds@linux-foundation.org>,
       "Pekka Enberg" <penberg@cs.helsinki.fi>, linux-kernel@vger.kernel.org,
       "Mel Gorman" <mel@csn.ul.ie>, "Nick Piggin" <npiggin@suse.de>,
       "Andrew Morton" <akpm@linux-foundation.org>,
       "Rafael J. Wysocki" <rjw@sisk.pl>, apw@shadowen.org,
       "KAMEZAWA Hiroyuki" <kamezawa.hiroyu@jp.fujitsu.com>
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On Tue, Apr 15, 2008 at 6:30 PM, Yinghai Lu <yhlu.kernel@gmail.com> wrote:
>
> On Tue, Apr 15, 2008 at 6:17 PM, Ingo Molnar <mingo@elte.hu> wrote:
>  >
>  >  * Ingo Molnar <mingo@elte.hu> wrote:
>  >
>  >  > > > this is the only call to memory_present() we do in 32-bit arch
>  >  > > > setup, so it's required.
>  >  > >
>  >  > > We could clip there if SPARSEMEM is configured. I wonder if this
>  >  > > affects other platforms that need HIGHMEM support?
>  >  >
>  >  > clip where and what?
>  >
>  >  i.e. as per my previous argument i'd consider the need to sanitize the
>  >  calls in the architecture fundamentally wrong.
>  >
>  >  whether the core code emits a warning or allows the call is an
>  >  additional question i mention in the changelog - but the core sparse
>  >  memory code should _definitely_ not silently overflow a key internal
>  >  array ... (of which data structure the architecture code is not even
>  >  aware of)
>
>  or you can move that check into find_max_pfn for x86_32? so it will
>  not affect other platform regarding Christoph's concern?
>
the patch doesn't have side effects on x86_64.

YH