linux-kernel - Re: [PATCH V3] iio: gp2ap020a00f: Fix signedness bug

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Date:   Thu, 28 Apr 2022 19:41:32 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Haowen Bai <baihaowen@...zu.com>
Cc:     Lars-Peter Clausen <lars@...afoo.de>, <linux-iio@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V3] iio: gp2ap020a00f: Fix signedness bug

On Mon, 18 Apr 2022 10:19:35 +0800
Haowen Bai <baihaowen@...zu.com> wrote:

> function gp2ap020a00f_get_thresh_reg() is unsigned but returning -EINVAL
> errcode, and thresh_reg_l is unsigned but receiving -EINVAL errcode. so
> we have to change u8 -> int. Also we need to do index bound check at
> gp2ap020a00f_read_event_val().
> 
> Signed-off-by: Haowen Bai <baihaowen@...zu.com>

Please add a Fixes tag if possible.

> ---
> V1->V2: s8 is not enough to hold an (arbitrary) error code. To be on the safe
> side we need to use int.
> V2->V3: add bound check at gp2ap020a00f_read_event_val().
> 
> 
>  drivers/iio/light/gp2ap020a00f.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iio/light/gp2ap020a00f.c b/drivers/iio/light/gp2ap020a00f.c
> index b820041159f7..f80d30786035 100644
> --- a/drivers/iio/light/gp2ap020a00f.c
> +++ b/drivers/iio/light/gp2ap020a00f.c
> @@ -994,7 +994,7 @@ static irqreturn_t gp2ap020a00f_trigger_handler(int irq, void *data)
>  	return IRQ_HANDLED;
>  }
>  
> -static u8 gp2ap020a00f_get_thresh_reg(const struct iio_chan_spec *chan,
> +static int gp2ap020a00f_get_thresh_reg(const struct iio_chan_spec *chan,
>  					     enum iio_event_direction event_dir)
>  {
>  	switch (chan->type) {
> @@ -1025,7 +1025,7 @@ static int gp2ap020a00f_write_event_val(struct iio_dev *indio_dev,
>  	struct gp2ap020a00f_data *data = iio_priv(indio_dev);
>  	bool event_en = false;
>  	u8 thresh_val_id;
> -	u8 thresh_reg_l;
> +	int thresh_reg_l;

You need to check this val after the function call, but before it is used.


>  	int err = 0;
>  
>  	mutex_lock(&data->lock);
> @@ -1082,14 +1082,14 @@ static int gp2ap020a00f_read_event_val(struct iio_dev *indio_dev,
>  				       int *val, int *val2)
>  {
>  	struct gp2ap020a00f_data *data = iio_priv(indio_dev);
> -	u8 thresh_reg_l;
> +	int thresh_reg_l;
>  	int err = IIO_VAL_INT;
>  
>  	mutex_lock(&data->lock);
>  
>  	thresh_reg_l = gp2ap020a00f_get_thresh_reg(chan, dir);
>  
> -	if (thresh_reg_l > GP2AP020A00F_PH_L_REG) {
> +	if (thresh_reg_l < 0 || thresh_reg_l > GP2AP020A00F_PH_L_REG) {
>  		err = -EINVAL;
If a function returns an error we should pass that on unchanged 
Here the value is the same, but none the less we should have this look something
like.

	if (thresh_reg_l < 0)
		return thresh_reg_l;
	if (thresh_reg_l > GP2AP020A00F_PH_L_REG)
	...

>  		goto error_unlock;
>  	}