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

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Date:	Wed, 24 Aug 2011 12:08:26 +0100
From:	Jamie Iles <jamie@...ieiles.com>
To:	Jason Liu <jason.hui@...aro.org>
Cc:	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

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.

>  		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.

Jamie
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