linux-kernel - Re: [PATCH] mtd: check parts pointer before using it

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Date:	Wed, 24 Aug 2011 19:12:05 +0800
From:	Jason Liu <liu.h.jason@...il.com>
To:	Jamie Iles <jamie@...ieiles.com>
Cc:	Jason Liu <jason.hui@...aro.org>,
	linux-arm-kernel@...ts.infradead.org, dedekind1@...il.com,
	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
	patches@...aro.org, David.Woodhouse@...el.com
Subject: Re: [PATCH] mtd: check parts pointer before using it

2011/8/24 Jamie Iles <jamie@...ieiles.com>:
> Hi Jason,
>
> On Wed, Aug 24, 2011 at 06:53:01PM +0800, Jason Liu wrote:
>> The code has the check for parts but it called after kmemdup,
>> kmemdup(parts, sizeof(*parts) * nr_parts,...)
>> if (!parts)
>>       return -ENOMEM
>>
>> In fact, we need check parts before safely using it.
>>
>> Signed-off-by: Jason Liu <jason.hui@...aro.org>
>> Cc: Dmitry Eremin-Solenikov <dbaryshkov@...il.com>
>> Cc: Artem Bityutskiy <artem.bityutskiy@...el.com>
>>
>> ---
>> This patch is based on git://git.infradead.org/users/dedekind/l2-mtd-2.6.git
>> ---
>>  drivers/mtd/mtdcore.c |    4 +---
>>  1 files changed, 1 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
>> index 09bdbac..ce59ff5 100644
>> --- a/drivers/mtd/mtdcore.c
>> +++ b/drivers/mtd/mtdcore.c
>> @@ -465,12 +465,10 @@ int mtd_device_parse_register(struct mtd_info *mtd, const char **types,
>>       struct mtd_partition *real_parts;
>>
>>       err = parse_mtd_partitions(mtd, types, &real_parts, parser_data);
>> -     if (err <= 0 && nr_parts) {
>> +     if (err <= 0 && nr_parts && !parts) {
>
> I don't think this is right.  Don't we want to check that parts is !=
> NULL?  So
>
>        if (err <= 0 && nr_parts && parts)
>
> instead?  We don't want to kmemdup() NULL.

My bad,  I type it error. Thanks for it.

>
>>               real_parts = kmemdup(parts, sizeof(*parts) * nr_parts,
>>                                    GFP_KERNEL);
>>               err = nr_parts;
>> -             if (!parts)
>> -                     err = -ENOMEM;
>
> I think this hunk should be changed to:
>
>                if (!real_parts)
>                        err = -ENOMEM;
>
> and keep the check so that we're checking kmemdup()'s allocation is
> successful.

Yes, correct. Thanks,

>
> Jamie
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