linux-kernel - Re: [PATCH] Fix potentially derefencing uninitialized 'r'.

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Date:	Mon, 20 Feb 2012 16:57:35 +0900
From:	Geunsik Lim <geunsik.lim@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Yinghai Lu <yinghai@...nel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>
Subject: Re: [PATCH] Fix potentially derefencing uninitialized 'r'.

On Sat, Feb 18, 2012 at 7:28 AM, Andrew Morton
<akpm@...ux-foundation.org> wrote:
> On Fri,  3 Feb 2012 17:20:56 +0900
> Geunsik Lim <geunsik.lim@...il.com> wrote:
>
>> struct memblock_region 'r' will not be initialized potentially
>> because of while statement's condition in __next_mem_pfn_range()function.
>> Initialize struct memblock_region data structure by default.
>>
>> Signed-off-by: Geunsik Lim <geunsik.lim@...sung.com>
>> ---
>>  mm/memblock.c |    2 +-
>>  1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/mm/memblock.c b/mm/memblock.c
>> index 77b5f22..867f5a2 100644
>> --- a/mm/memblock.c
>> +++ b/mm/memblock.c
>> @@ -671,7 +671,7 @@ void __init_memblock __next_mem_pfn_range(int *idx, int nid,
>>                               unsigned long *out_end_pfn, int *out_nid)
>>  {
>>       struct memblock_type *type = &memblock.memory;
>> -     struct memblock_region *r;
>> +     struct memblock_region *r = &type->regions[*idx];
>>
>>       while (++*idx < type->cnt) {
>>               r = &type->regions[*idx];
>
> The following `if' test prevents any such dereference.
>
> Maybe you saw a compilation warning (I didn't).  If so,
> unintialized_var() is one way of suppressing it.
Yepp. This patch is  for solving compilation warning as you commented.
>
> A better way is to reorganise the code (nicely).  Often that option
> isn't available.
I will post patch again after reorganizing the code with better way.
Thanks.
>
>



-- 
----
Best regards,
Geunsik Lim, Samsung Electronics
http://leemgs.fedorapeople.org
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