[PATCH] media: i2c: fix an uninitialized error code

[PATCH] media: i2c: fix an uninitialized error code

[Arnd Bergmann]

From: Arnd Bergmann <arnd@arndb.de>

Clang points out that the error handling in ov02a10_s_stream() is
broken, and just returns a random error code:

drivers/media/i2c/ov02a10.c:537:6: warning: variable 'ret' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
        if (ov02a10->streaming == on)
            ^~~~~~~~~~~~~~~~~~~~~~~~
drivers/media/i2c/ov02a10.c:568:9: note: uninitialized use occurs here
        return ret;
               ^~~
drivers/media/i2c/ov02a10.c:537:2: note: remove the 'if' if its condition is always false
        if (ov02a10->streaming == on)
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/media/i2c/ov02a10.c:533:9: note: initialize the variable 'ret' to silence this warning
        int ret;

I assume that -EBUSY is the intended error code, so use that.

Fixes: 91807efbe8ec ("media: i2c: add OV02A10 image sensor driver")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/media/i2c/ov02a10.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/media/i2c/ov02a10.c b/drivers/media/i2c/ov02a10.c
index 391718136ade..7ee9c904d9b5 100644
--- a/drivers/media/i2c/ov02a10.c
+++ b/drivers/media/i2c/ov02a10.c
@@ -534,8 +534,10 @@ static int ov02a10_s_stream(struct v4l2_subdev *sd, int on)
 
 	mutex_lock(&ov02a10->mutex);
 
-	if (ov02a10->streaming == on)
+	if (ov02a10->streaming == on) {
+		ret = -EBUSY;
 		goto unlock_and_return;
+	}
 
 	if (on) {
 		ret = pm_runtime_get_sync(&client->dev);
-- 
2.27.0

Re: [PATCH] media: i2c: fix an uninitialized error code

[Dongchun Zhu]

Hi Arnd,

Thanks for the patch.

On Thu, 2020-12-03 at 23:29 +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> Clang points out that the error handling in ov02a10_s_stream() is
> broken, and just returns a random error code:
> 
> drivers/media/i2c/ov02a10.c:537:6: warning: variable 'ret' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
>         if (ov02a10->streaming == on)
>             ^~~~~~~~~~~~~~~~~~~~~~~~
> drivers/media/i2c/ov02a10.c:568:9: note: uninitialized use occurs here
>         return ret;
>                ^~~
> drivers/media/i2c/ov02a10.c:537:2: note: remove the 'if' if its condition is always false
>         if (ov02a10->streaming == on)
>         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/media/i2c/ov02a10.c:533:9: note: initialize the variable 'ret' to silence this warning
>         int ret;
> 
> I assume that -EBUSY is the intended error code, so use that.
> 
> Fixes: 91807efbe8ec ("media: i2c: add OV02A10 image sensor driver")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  drivers/media/i2c/ov02a10.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/i2c/ov02a10.c b/drivers/media/i2c/ov02a10.c
> index 391718136ade..7ee9c904d9b5 100644
> --- a/drivers/media/i2c/ov02a10.c
> +++ b/drivers/media/i2c/ov02a10.c
> @@ -534,8 +534,10 @@ static int ov02a10_s_stream(struct v4l2_subdev *sd, int on)
>  
>  	mutex_lock(&ov02a10->mutex);
>  
> -	if (ov02a10->streaming == on)
> +	if (ov02a10->streaming == on) {
> +		ret = -EBUSY;
>  		goto unlock_and_return;
> +	}
>  
>  	if (on) {
>  		ret = pm_runtime_get_sync(&client->dev);

Only if sensor fails to stream on, ret can return a negative error code.
Thus ret above needs to be initialized to '0'.
Also you could fix the clang error like this.

static int ov02a10_s_stream(struct v4l2_subdev *sd, int on)
{
	struct ov02a10 *ov02a10 = to_ov02a10(sd);
	...
	int ret = 0;

	...
	if (ov02a10->streaming == on)
		goto unlock_and_return;

	...
}

Re: [PATCH] media: i2c: fix an uninitialized error code

[Arnd Bergmann]

On Fri, Dec 4, 2020 at 3:10 AM Dongchun Zhu <dongchun.zhu@mediatek.com> wrote:
>
> Hi Arnd,
>
> Thanks for the patch.
>
> On Thu, 2020-12-03 at 23:29 +0100, Arnd Bergmann wrote:
> > From: Arnd Bergmann <arnd@arndb.de>
> >
> > Clang points out that the error handling in ov02a10_s_stream() is
> > broken, and just returns a random error code:
> >
> > drivers/media/i2c/ov02a10.c:537:6: warning: variable 'ret' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
> >         if (ov02a10->streaming == on)
> >             ^~~~~~~~~~~~~~~~~~~~~~~~
> > drivers/media/i2c/ov02a10.c:568:9: note: uninitialized use occurs here
> >         return ret;
> >                ^~~
> > drivers/media/i2c/ov02a10.c:537:2: note: remove the 'if' if its condition is always false
> >         if (ov02a10->streaming == on)
> >         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > drivers/media/i2c/ov02a10.c:533:9: note: initialize the variable 'ret' to silence this warning
> >         int ret;
> >
> > I assume that -EBUSY is the intended error code, so use that.
> >
> > Fixes: 91807efbe8ec ("media: i2c: add OV02A10 image sensor driver")
> > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> > ---
> >  drivers/media/i2c/ov02a10.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/media/i2c/ov02a10.c b/drivers/media/i2c/ov02a10.c
> > index 391718136ade..7ee9c904d9b5 100644
> > --- a/drivers/media/i2c/ov02a10.c
> > +++ b/drivers/media/i2c/ov02a10.c
> > @@ -534,8 +534,10 @@ static int ov02a10_s_stream(struct v4l2_subdev *sd, int on)
> >
> >       mutex_lock(&ov02a10->mutex);
> >
> > -     if (ov02a10->streaming == on)
> > +     if (ov02a10->streaming == on) {
> > +             ret = -EBUSY;
> >               goto unlock_and_return;
> > +     }
> >
> >       if (on) {
> >               ret = pm_runtime_get_sync(&client->dev);
>
> Only if sensor fails to stream on, ret can return a negative error code.
> Thus ret above needs to be initialized to '0'.

Ok, I sent a version 2.

> Also you could fix the clang error like this.
>
> static int ov02a10_s_stream(struct v4l2_subdev *sd, int on)
> {
>         struct ov02a10 *ov02a10 = to_ov02a10(sd);
>         ...
>         int ret = 0;
>
>         ...
>         if (ov02a10->streaming == on)
>                 goto unlock_and_return;
>
>         ...
> }

Sorry, I should have removed the last line of the output from
clang that suggested doing that. Initializing a local variable
in the declaration is generally a bad idea precisely because it
prevents the compiler from warning about a case like this where
the author forgot to set the correct error value.

We should really fix clang to not propagate that nonsense.

        Arnd