linux-kernel - Re: [PATCH 1/2] media: i2c: ds90ub9x3: Fix use of uninitialized variables

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Date:   Fri, 4 Aug 2023 00:46:46 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Hans Verkuil <hverkuil@...all.nl>, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] media: i2c: ds90ub9x3: Fix use of uninitialized
 variables

Hi Tomi,

Thank you for the patch.

On Thu, Aug 03, 2023 at 11:41:38AM +0300, Tomi Valkeinen wrote:
> smatch reports some uninitialized variables:
> 
> drivers/media/i2c/ds90ub913.c:481 ub913_log_status() error: uninitialized symbol 'v1'.
> drivers/media/i2c/ds90ub913.c:481 ub913_log_status() error: uninitialized symbol 'v2'.
> drivers/media/i2c/ds90ub953.c:655 ub953_log_status() error: uninitialized symbol 'gpio_local_data'.
> drivers/media/i2c/ds90ub953.c:655 ub953_log_status() error: uninitialized symbol 'gpio_input_ctrl'.
> drivers/media/i2c/ds90ub953.c:655 ub953_log_status() error: uninitialized symbol 'gpio_pin_sts'.
> 
> These are used only for printing debug information, and the use of an
> uninitialized variable only happens if an i2c transaction has failed,
> which will print an error. Thus, fix the errors just by initializing the
> variables to 0.
> 
> Fixes: 6363db1c9d45 ("media: i2c: add DS90UB953 driver")
> Fixes: c158d0d4ff15 ("media: i2c: add DS90UB913 driver")
> Reported-by: Hans Verkuil <hverkuil@...all.nl>
> Closes: https://lore.kernel.org/all/8d6daeb1-b62a-bbb2-b840-8759c84f2085@xs4all.nl/
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
> ---
>  drivers/media/i2c/ds90ub913.c | 2 +-
>  drivers/media/i2c/ds90ub953.c | 6 +++---
>  2 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/media/i2c/ds90ub913.c b/drivers/media/i2c/ds90ub913.c
> index 80d9cf6dd945..b2115e3519e2 100644
> --- a/drivers/media/i2c/ds90ub913.c
> +++ b/drivers/media/i2c/ds90ub913.c
> @@ -469,7 +469,7 @@ static int ub913_log_status(struct v4l2_subdev *sd)
>  {
>  	struct ub913_data *priv = sd_to_ub913(sd);
>  	struct device *dev = &priv->client->dev;
> -	u8 v = 0, v1, v2;
> +	u8 v = 0, v1 = 0, v2 = 0;

This seems to work around the lack of error checking when calling
ub913_read(). Wouldn't it be better to check for errors there ? Or,
because this is ub913_log_status(), do you consider that we can print an
invalid CRC errors count, given that the ub913_read() function will have
printed an error message before ?

>  
>  	ub913_read(priv, UB913_REG_MODE_SEL, &v);
>  	dev_info(dev, "MODE_SEL %#02x\n", v);
> diff --git a/drivers/media/i2c/ds90ub953.c b/drivers/media/i2c/ds90ub953.c
> index cadf75eb0773..27471249a62a 100644
> --- a/drivers/media/i2c/ds90ub953.c
> +++ b/drivers/media/i2c/ds90ub953.c
> @@ -593,9 +593,9 @@ static int ub953_log_status(struct v4l2_subdev *sd)
>  	u8 v = 0, v1 = 0, v2 = 0;
>  	unsigned int i;
>  	char id[UB953_REG_FPD3_RX_ID_LEN];
> -	u8 gpio_local_data;
> -	u8 gpio_input_ctrl;
> -	u8 gpio_pin_sts;
> +	u8 gpio_local_data = 0;
> +	u8 gpio_input_ctrl = 0;
> +	u8 gpio_pin_sts = 0;
>  
>  	for (i = 0; i < sizeof(id); i++)
>  		ub953_read(priv, UB953_REG_FPD3_RX_ID(i), &id[i]);
> 

-- 
Regards,

Laurent Pinchart