linux-kernel - Re: [PATCH V4] iio: gp2ap020a00f: Fix signedness bug

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Message-ID: <20220501160317.62d4737c@jic23-huawei>
Date:   Sun, 1 May 2022 16:03:17 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Haowen Bai <baihaowen@...zu.com>
Cc:     <lars@...afoo.de>, <linux-iio@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V4] iio: gp2ap020a00f: Fix signedness bug

On Fri, 29 Apr 2022 09:36:54 +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>
Hi Haowen Bai,

Please add a fixes tag.  Also, this thread is getting rather deep
and illustrates why I tend to ask for each new version of IIO patches
to be posted without replying to previous thread (so start a new thread).

One issue below with locking.

Thanks,

Jonathan

> ---
> 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().
> V3->V4: 
> 1. add fix tag.
> 2. add check before use at gp2ap020a00f_write_event_val().
> 3. returns an error we should pass that on unchanged at
> gp2ap020a00f_read_event_val()
> 
>  drivers/iio/light/gp2ap020a00f.c | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iio/light/gp2ap020a00f.c b/drivers/iio/light/gp2ap020a00f.c
> index b820041159f7..13583e1191d4 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) {
> @@ -1025,12 +1025,18 @@ 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;
>  	int err = 0;
>  
>  	mutex_lock(&data->lock);
>  
>  	thresh_reg_l = gp2ap020a00f_get_thresh_reg(chan, dir);
> +
> +	if (thresh_reg_l < 0){
> +		err = thresh_reg_l;
> +		goto error_unlock;
> +	}
> +
>  	thresh_val_id = GP2AP020A00F_THRESH_VAL_ID(thresh_reg_l);
>  
>  	if (thresh_val_id > GP2AP020A00F_THRESH_PH) {
> @@ -1082,13 +1088,16 @@ 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 < 0)
mutex_unlock() ?

I'd expect something like
	if (thresh_reg_l < 0) {
		err = thresh_reg_l;
		goto error_unlock;
	}

> +		return thresh_reg_l;
> +
>  	if (thresh_reg_l > GP2AP020A00F_PH_L_REG) {
>  		err = -EINVAL;
>  		goto error_unlock;