linux-kernel - Re: [PATCH v6] staging: atomisp: move null check to earlier point

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Date:   Thu, 06 Aug 2020 21:34:22 +0300
From:   Cengiz Can <cengiz@...nel.wtf>
To:     <andy.shevchenko@...il.com>
CC:     <dan.carpenter@...cle.com>, <devel@...verdev.osuosl.org>,
        <gregkh@...uxfoundation.org>, <linux-kernel@...r.kernel.org>,
        <linux-media@...r.kernel.org>, <mchehab@...nel.org>,
        <sakari.ailus@...ux.intel.com>, Cengiz Can <cengiz@...nel.wtf>
Subject: Re: [PATCH v6] staging: atomisp: move null check to earlier point

Hello Andy,

Can I get some feedback on v6 please?

I hope it suits your standards this time.

Thank you

On August 2, 2020 01:02:22 Cengiz Can <cengiz@...nel.wtf> wrote:

> `find_gmin_subdev()` that returns a pointer to `struct
> gmin_subdev` can return NULL.
>
> In `gmin_v2p8_ctrl()` there's a call to this function but the
> possibility of a NULL was not checked before its being dereferenced,
> i.e.:
>
>  /* Acquired here --------v */
>  struct gmin_subdev *gs = find_gmin_subdev(subdev);
>
>  /*  v------Dereferenced here */
>  if (gs->v2p8_gpio >= 0) {
>      ...
>  }
>
> With this change we're null checking `find_gmin_subdev()` result
> and we return an error if that's the case. We also WARN()
> for the sake of debugging.
>
> Signed-off-by: Cengiz Can <cengiz@...nel.wtf>
> Reported-by: Coverity Static Analyzer CID 1465536
> Suggested-by: Mauro Carvalho Chehab <mchehab@...nel.org>
> ---
>
> Please do note that this change introduces a new return value to
> `gmin_v2p8_ctrl()`.
>
> [NEW] - raise a WARN and return -ENODEV if there are no subdevices.
>       - return result of `gpio_request` or `gpio_direction_output`.
>       - return 0 if GPIO is ON.
>       - return results of `regulator_enable` or `regulator_disable`.
>       - according to PMIC type, return result of `axp_regulator_set`
>         or `gmin_i2c_write`.
>       - return -EINVAL if unknown PMIC type.
>
> Patch Changelog:
>   v4: Fix minor typo in commit message
>   v5: Remove typo from email subject
>   v6: Remove duplicate Signed-off-by tag
>
> drivers/staging/media/atomisp/pci/atomisp_gmin_platform.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/staging/media/atomisp/pci/atomisp_gmin_platform.c 
> b/drivers/staging/media/atomisp/pci/atomisp_gmin_platform.c
> index 0df46a1af5f0..1ad0246764a6 100644
> --- a/drivers/staging/media/atomisp/pci/atomisp_gmin_platform.c
> +++ b/drivers/staging/media/atomisp/pci/atomisp_gmin_platform.c
> @@ -871,6 +871,9 @@ static int gmin_v2p8_ctrl(struct v4l2_subdev *subdev, 
> int on)
> 	int ret;
> 	int value;
>
> +	if (WARN_ON(!gs))
> +		return -ENODEV;
> +
> 	if (gs->v2p8_gpio >= 0) {
> 		pr_info("atomisp_gmin_platform: 2.8v power on GPIO %d\n",
> 			gs->v2p8_gpio);
> @@ -881,7 +884,7 @@ static int gmin_v2p8_ctrl(struct v4l2_subdev *subdev, 
> int on)
> 			pr_err("V2P8 GPIO initialization failed\n");
> 	}
>
> -	if (!gs || gs->v2p8_on == on)
> +	if (gs->v2p8_on == on)
> 		return 0;
> 	gs->v2p8_on = on;
>
> --
> 2.27.0