re: media: i2c: add OV02A10 image sensor driver

re: media: i2c: add OV02A10 image sensor driver

[Colin Ian King]

Hi,

Static analysis on linux-next with Coverity has detected an issue with
the following commit:

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;
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;
559        mutex_unlock(&ov02a10->mutex);
560
561        return 0;
562
563 err_rpm_put:
564        pm_runtime_put(&client->dev);
565 unlock_and_return:
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.

Colin

Re: media: i2c: add OV02A10 image sensor driver

[Andy Shevchenko]

On Thu, Dec 3, 2020 at 8:03 PM Colin Ian King <colin.king@canonical.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.

-- 
With Best Regards,
Andy Shevchenko

Re: media: i2c: add OV02A10 image sensor driver

[Colin Ian King]

On 03/12/2020 18:10, Andy Shevchenko wrote:
> On Thu, Dec 3, 2020 at 8:03 PM Colin Ian King <colin.king@canonical.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. 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).

Colin

Re: media: i2c: add OV02A10 image sensor driver

[Andy Shevchenko]

On Thu, Dec 3, 2020 at 8:24 PM Colin Ian King <colin.king@canonical.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@canonical.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

Re: media: i2c: add OV02A10 image sensor driver

[Dongchun Zhu]

Hi Andy,

On Thu, 2020-12-03 at 20:10 +0200, Andy Shevchenko wrote:
> On Thu, Dec 3, 2020 at 8:03 PM Colin Ian King <colin.king@canonical.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:

From the document, pm_runtime_put_noidle is to decrease the runtime PM
usage counter of a device unless it is 0 already; while pm_runtime_put
would additionally run pm_request_idle to turn off the power if usage
counter is zero.

So here maybe we can really use pm_runtime_put instead of
pm_runtime_put_noidle, although it seems that 'pm_runtime_get_sync' and
'pm_runtime_put_noidle' often appear in pairs.

>                        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.
> 

Re: media: i2c: add OV02A10 image sensor driver

[Tomasz Figa]

On Fri, Dec 4, 2020 at 11:47 AM Dongchun Zhu <dongchun.zhu@mediatek.com> wrote:
>
> Hi Andy,
>
> On Thu, 2020-12-03 at 20:10 +0200, Andy Shevchenko wrote:
> > On Thu, Dec 3, 2020 at 8:03 PM Colin Ian King <colin.king@canonical.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:
>
> From the document, pm_runtime_put_noidle is to decrease the runtime PM
> usage counter of a device unless it is 0 already; while pm_runtime_put
> would additionally run pm_request_idle to turn off the power if usage
> counter is zero.
>
> So here maybe we can really use pm_runtime_put instead of
> pm_runtime_put_noidle, although it seems that 'pm_runtime_get_sync' and
> 'pm_runtime_put_noidle' often appear in pairs.
>

In an error state (e.g. if pm_runtime_get_sync() fails),
pm_runtime_put() would decrement the usage counter and call rpm_idle()
which would instantly return an error code. The end result would be
the same, except that pm_runtime_put() would return a non-zero error
code, but we ignore it anyway. However strange it looks, this seems to
be an API guarantee, so Andy's suggestion is correct.

Best regards,
Tomasz

> >                        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.
> >
>

Re: media: i2c: add OV02A10 image sensor driver

[Sakari Ailus]

On Thu, Dec 03, 2020 at 08:30:03PM +0200, Andy Shevchenko wrote:
> On Thu, Dec 3, 2020 at 8:24 PM Colin Ian King <colin.king@canonical.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@canonical.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.

Arnd sent a patch to address this:

<URL:https://patchwork.linuxtv.org/project/linux-media/patch/20201204082037.1658297-1-arnd@kernel.org/>

-- 
Sakari Ailus