linux-kernel - Re: [PATCH] staging:iio: Use kcalloc instead of kzalloc to allocate array

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Date:	Wed, 30 Nov 2011 09:35:23 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Thomas Meyer <thomas@...3r.de>
Cc:	gregkh@...e.de, linux-iio@...r.kernel.org,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging:iio: Use kcalloc instead of kzalloc to allocate
 array

On Tue, Nov 29, 2011 at 10:08:00PM +0100, Thomas Meyer wrote:
> The advantage of kcalloc is, that will prevent integer overflows which could
> result from the multiplication of number of elements and size and it is also
> a bit nicer to read.
> 
> The semantic patch that makes this change is available
> in https://lkml.org/lkml/2011/11/25/107
> 
> Signed-off-by: Thomas Meyer <thomas@...3r.de>
> ---
> 
> diff -u -p a/drivers/staging/iio/accel/lis3l02dq_ring.c b/drivers/staging/iio/accel/lis3l02dq_ring.c
> --- a/drivers/staging/iio/accel/lis3l02dq_ring.c 2011-11-13 11:07:47.933826988 +0100
> +++ b/drivers/staging/iio/accel/lis3l02dq_ring.c 2011-11-28 20:00:44.704446880 +0100
> @@ -93,8 +93,7 @@ static int lis3l02dq_read_all(struct iio
>  	struct spi_message msg;
>  	int ret, i, j = 0;
>  
> -	xfers = kzalloc((buffer->scan_count) * 2
> -			* sizeof(*xfers), GFP_KERNEL);
> +	xfers = kcalloc((buffer->scan_count) * 2, sizeof(*xfers), GFP_KERNEL);

I've looked at these and none of them can actually overflow.

But if they could then there would still be the potential for
overflow here.  If buffer->scan_count were a negative number then
the first for loop could cause memory corruption.

Still it's a cleanup and the patch is fine.

regards,
dan carpenter

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