linux-kernel - Re: media: i2c: add OV02A10 image sensor driver

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Date:   Thu, 3 Dec 2020 20:30:03 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Colin Ian King <colin.king@...onical.com>
Cc:     Dongchun Zhu <dongchun.zhu@...iatek.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-media <linux-media@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: media: i2c: add OV02A10 image sensor driver

On Thu, Dec 3, 2020 at 8:24 PM Colin Ian King <colin.king@...onical.com> wrote:
> On 03/12/2020 18:10, Andy Shevchenko wrote:
> > On Thu, Dec 3, 2020 at 8:03 PM Colin Ian King <colin.king@...onical.com> wrote:
> >
> >> Static analysis on linux-next with Coverity has detected an issue with
> >> the following commit:
> >
> > If you want to fix it properly, see my comments below...
> >
> >> 529 static int ov02a10_s_stream(struct v4l2_subdev *sd, int on)
> >> 530 {
> >> 531        struct ov02a10 *ov02a10 = to_ov02a10(sd);
> >> 532        struct i2c_client *client =
> >> v4l2_get_subdevdata(&ov02a10->subdev);
> >>
> >>    1. var_decl: Declaring variable ret without initializer.
> >>
> >> 533        int ret;
> >> 534
> >> 535        mutex_lock(&ov02a10->mutex);
> >> 536
> >>
> >>    2. Condition ov02a10->streaming == on, taking true branch.
> >>
> >> 537        if (ov02a10->streaming == on)
> >>
> >>    3. Jumping to label unlock_and_return.
> >>
> >> 538                goto unlock_and_return;
> >> 539
> >> 540        if (on) {
> >> 541                ret = pm_runtime_get_sync(&client->dev);
> >> 542                if (ret < 0) {
> >
> >> 543                        pm_runtime_put_noidle(&client->dev);
> >> 544                        goto unlock_and_return;
> >
> > Instead of two above:
> >                        goto err_rpm_put;
> >
> >> 545                }
> >> 546
> >> 547                ret = __ov02a10_start_stream(ov02a10);
> >> 548                if (ret) {
> >> 549                        __ov02a10_stop_stream(ov02a10);
> >> 550                        ov02a10->streaming = !on;
> >> 551                        goto err_rpm_put;
> >> 552                }
> >> 553        } else {
> >> 554                __ov02a10_stop_stream(ov02a10);
> >> 555                pm_runtime_put(&client->dev);
> >> 556        }
> >> 557
> >> 558        ov02a10->streaming = on;
> >
> > (1)
> >
> >> 559        mutex_unlock(&ov02a10->mutex);
> >> 560
> >> 561        return 0;
> >> 562
> >> 563 err_rpm_put:
> >> 564        pm_runtime_put(&client->dev);
> >
> >> 565 unlock_and_return:
> >
> > Should be moved to (1).
> >
> >> 566        mutex_unlock(&ov02a10->mutex);
> >> 567
> >>
> >> Uninitialized scalar variable (UNINIT)
> >>     4. uninit_use: Using uninitialized value ret.
> >>
> >> 568        return ret;
> >> 569 }
> >>
> >> Variable ret has not been initialized, so the error return value is a
> >> garbage value. It should be initialized with some appropriate negative
> >> error code, or ret could be removed and the return should return a
> >> literal value of a error code.
> >>
> >> I was unsure what value is appropriate to fix this, so instead I'm
> >> reporting this issue.
> >
> Not sure I fully understand how that fixes it.

If you are not sure and have no means to test, then don't bother. This
is not the priority driver anyway.

>  Given that ret is
> currently not initialized when we hit:
>
>          if (ov02a10->streaming == on)
>                 goto unlock_and_return;
>
> either we initialize ret to 0 at the start of the function, or do:
>
>          if (ov02a10->streaming == on) {
>                 ret = 0;
>                 goto unlock_and_return;
>         }
>
> (assuming the intention is to return zero for this specific case).

No, please read my message again.

-- 
With Best Regards,
Andy Shevchenko