linux-kernel - Re: [patch] mm: sparsemem memory_present() memory corruption fix

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Date:	Wed, 16 Apr 2008 02:34:49 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Pekka Enberg <penberg@...helsinki.fi>,
	Christoph Lameter <clameter@....com>,
	linux-kernel@...r.kernel.org, Mel Gorman <mel@....ul.ie>,
	Nick Piggin <npiggin@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Yinghai.Lu@....com,
	apw@...dowen.org,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [patch] mm: sparsemem memory_present() memory corruption fix


small addendum to the changelog:

>                 if (!ms->section_mem_map)
>                         ms->section_mem_map = sparse_encode_early_nid(nid) |
+                                            | SECTION_MARKED_PRESENT
> 
> 'ms' will be out of bounds and we'll corrupt a small amount of memory by
> encoding the node ID. Depending on what that memory is, we might crash, 
> misbehave or just not notice the bug.

the corruption might happen when encoding a non-zero node ID, or due to 
the SECTION_MARKED_PRESENT which is 0x1:

mmzone.h:#define        SECTION_MARKED_PRESENT  (1UL<<0)

	Ingo
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