linux-kernel - Re: [PATCH v4] mm/memblock: fix overlapping allocation when doubling reserved array

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Date:	Tue, 19 Jun 2012 22:35:08 +0000
From:	"Pearson, Greg" <greg.pearson@...com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	"tj@...nel.org" <tj@...nel.org>,
	"hpa@...ux.intel.com" <hpa@...ux.intel.com>,
	"shangw@...ux.vnet.ibm.com" <shangw@...ux.vnet.ibm.com>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"yinghai@...nel.org" <yinghai@...nel.org>,
	"benh@...nel.crashing.org" <benh@...nel.crashing.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] mm/memblock: fix overlapping allocation when
 doubling reserved array

On 06/19/2012 04:14 PM, Andrew Morton wrote:
> On Mon, 18 Jun 2012 17:47:58 -0600
> Greg Pearson <greg.pearson@...com> wrote:
>
>> The __alloc_memory_core_early() routine will ask memblock for a range
>> of memory then try to reserve it. If the reserved region array lacks
>> space for the new range, memblock_double_array() is called to allocate
>> more space for the array. If memblock is used to allocate memory for
>> the new array it can end up using a range that overlaps with the range
>> originally allocated in __alloc_memory_core_early(), leading to possible
>> data corruption.
> OK, but we have no information about whether it *does* lead to data
> corruption.  Are there workloads which trigger this?  End users who are
> experiencing problems?
>
> See, I (and others) need to work out whether this patch should be
> included in 3.5 or even earlier kernels.  To do that we often need the
> developer to tell us what the impact of the bug is upon users.  Please
> always include this info when fixing bugs.

Andrew,

I'm currently working on a prototype system that exhibits the data 
corruption problem when doubling the reserved array while booting the 
system. This system will be a released product in the future. I'll 
remember to include this information in the patch next time.

Thanks

--
Greg--
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