Re: [PATCH] staging: atomisp: move null check to earlier point

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On July 30, 2020 11:48:06 Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:

On Wed, Jul 29, 2020 at 06:13:44PM +0300, Andy Shevchenko wrote:
On Wed, Jul 29, 2020 at 5:00 PM Cengiz Can <cengiz@xxxxxxxxxx> wrote:

`find_gmin_subdev` function 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. ie:

```
/* Acquired here --------v */
struct gmin_subdev *gs = find_gmin_subdev(subdev);
int ret;
int value;

/*  v------Dereferenced here */
if (gs->v2p8_gpio >= 0) {
 pr_info("atomisp_gmin_platform: 2.8v power on GPIO %d\n",
         gs->v2p8_gpio);
 ret = gpio_request(gs->v2p8_gpio, "camera_v2p8");
 if (!ret)
         ret = gpio_direction_output(gs->v2p8_gpio, 0);
 if (ret)
         pr_err("V2P8 GPIO initialization failed\n");
}
```

I have moved the NULL check before deref point.

"Move the NULL check..."
See Submitting Patches documentation how to avoid "This patch", "I", "we", etc.

Noted. Sorry. I'm not a native English speaker.



I always feel like this is a pointless requirement.  We're turning into
bureaucracts.


diff --git a/drivers/staging/media/atomisp/pci/atomisp_gmin_platform.c b/drivers/staging/media/atomisp/pci/atomisp_gmin_platform.c
index 0df46a1af5f0..8e9c5016f299 100644
--- a/drivers/staging/media/atomisp/pci/atomisp_gmin_platform.c
+++ b/drivers/staging/media/atomisp/pci/atomisp_gmin_platform.c
@@ -871,6 +871,11 @@ static int gmin_v2p8_ctrl(struct v4l2_subdev *subdev, int on)
 int ret;
 int value;

+       if (!gs) {
+               pr_err("Unable to find gmin subdevice\n");

+               return -EINVAL;

And here is a change of semantics...

Yeah.  The change of semantics should be documented in the commit
message, but it's actually correct.  I discussed this with Mauro earlier
but my bug reporting script didn't CC a mailing list and I didn't
catch it.  Mauro suggested:

   53  > Yet, it could make sense to have something like:
   54  >
   55  >       if (WARN_ON(!gs))
   56  >               return -ENODEV;
   57  >
   58  > at the beginning of the functions that call find_gmin_subdev().

I will be updating v2 according to this.


regards,
dan carpenter



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