Re: [PATCH] mm: __nr_to_section - make it safe against overflow v2

[KAMEZAWA Hiroyuki]

On Tue, 6 Jan 2009 14:57:41 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:

> On Mon, 5 Jan 2009 16:37:42 -0800
> Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
> 
> > On Mon, 5 Jan 2009 13:31:32 +0300
> > Cyrill Gorcunov <gorcunov@xxxxxxxxx> wrote:
> > 
> > > __nr_to_section should check for array bound overflow.
> > > We should better get NULL dereference then silently
> > > pass some memory snippet out of bounds to a caller.
> > > 
> > 
> > Are there actually any known problems here?
> > 
> 
> IIRC, I never saw any problem. (But I may see in memory-hotplug development.)

I digged mails and seems this patch is from this thread.

=
http://lkml.org/lkml/2009/1/4/61
=

He seems to want to hunt boot time failure.
(Finally, BIOS-update was necessary for original problem of this thread.)

Cyrill, could you modify this WARN_ON() works works when __nr_to_section()
is called directly by sparse.c and memhotplug.c ?

Adding WARN_ON() in pfn_to_page() is overkill.

Thanks,
-Kame

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