linux-kernel - Re: [PATCH] iio/adjd_s311: Fix potential memory leak in adjd_s311_update_scan

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Date:	Wed, 8 Aug 2012 09:17:09 +0200 (CEST)
From:	Peter Meerwald <pmeerw@...erw.net>
To:	Alexey Khoroshilov <khoroshilov@...ras.ru>
cc:	Jonathan Cameron <jic23@....ac.uk>, linux-iio@...r.kernel.org,
	linux-kernel@...r.kernel.org, ldv-project@...ras.ru,
	Lars-Peter Clausen <lars@...afoo.de>
Subject: Re: [PATCH] iio/adjd_s311: Fix potential memory leak in
 adjd_s311_update_scan_mode()


> Do not leak memory by updating pointer with potentially
> NULL realloc return value.

I agree

use of krealloc() was suggested in driver review (see 
http://www.spinics.net/lists/linux-iio/msg05930.html) to shorten the code; 
unfortunately, I misunderstood the semantics of krealloc() in case 
allocation fails

this is the original code:

	kfree(data->buffer);
	data->buffer = kmalloc(indio_dev->scan_bytes, GFP_KERNEL);
	if (!data->buffer)
		return -ENOMEM;

I suggest to switch back to that original code, there is no need preserve 
the data in the buffer as krealloc does

thanks, p.

> Found by Linux Driver Verification project (linuxtesting.org).
> 
> Signed-off-by: Alexey Khoroshilov <khoroshilov@...ras.ru>
> ---
>  drivers/iio/light/adjd_s311.c |   14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iio/light/adjd_s311.c b/drivers/iio/light/adjd_s311.c
> index 1cbb449..0adda5b 100644
> --- a/drivers/iio/light/adjd_s311.c
> +++ b/drivers/iio/light/adjd_s311.c
> @@ -271,12 +271,18 @@ static int adjd_s311_update_scan_mode(struct iio_dev *indio_dev,
>  	const unsigned long *scan_mask)
>  {
>  	struct adjd_s311_data *data = iio_priv(indio_dev);
> -	data->buffer = krealloc(data->buffer, indio_dev->scan_bytes,
> +	u16 *new_buffer;
> +	int ret = 0;
> +
> +	new_buffer = krealloc(data->buffer, indio_dev->scan_bytes,
>  				GFP_KERNEL);
> -	if (!data->buffer)
> -		return -ENOMEM;
> +	if (new_buffer == NULL) {
> +		kfree(data->buffer);
> +		ret = -ENOMEM;
> +	}
> +	data->buffer = new_buffer;
>  
> -	return 0;
> +	return ret;
>  }
>  
>  static const struct iio_info adjd_s311_info = {
> 

-- 

Peter Meerwald
+43-664-2444418 (mobile)
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