linux-kernel - Re: [PATCH] iio: ad5755: fix off-by-one on devnr limit check

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Date:   Sun, 21 Aug 2016 20:30:35 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Colin King <colin.king@...onical.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Hartmut Knaack <knaack.h@....de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        linux-iio@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: ad5755: fix off-by-one on devnr limit check

On 25/07/16 23:40, Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
> 
> The comparison for devnr limits is off-by-one, the current check
> allows 0 to AD5755_NUM_CHANNELS and the limit should be in fact
> 0 to AD5755_NUM_CHANNELS - 1.  This can lead to an out of bounds
> write to pdata->dac[devnr]. Fix this by replacing > with >= on the
> comparison.
> 
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
Lars? 

Looks correct to me.

I'd also like a fixes tag for this if possible.  Guessing it
might well be the original driver introduction but best to be
sure ;)

Jonathan
> ---
>  drivers/iio/dac/ad5755.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/dac/ad5755.c b/drivers/iio/dac/ad5755.c
> index 0fde593..5f79682 100644
> --- a/drivers/iio/dac/ad5755.c
> +++ b/drivers/iio/dac/ad5755.c
> @@ -655,7 +655,7 @@ static struct ad5755_platform_data *ad5755_parse_dt(struct device *dev)
>  
>  	devnr = 0;
>  	for_each_child_of_node(np, pp) {
> -		if (devnr > AD5755_NUM_CHANNELS) {
> +		if (devnr >= AD5755_NUM_CHANNELS) {
>  			dev_err(dev,
>  				"There is to many channels defined in DT\n");
>  			goto error_out;
>