Re: [PATCH 03/14] media: ov6650: Fix unverified arguments used in .set_fmt()

Janusz Krzysztofik
2019-05-07T23:33:30Z

Hi Sakari,

Sorry for late answer, I've just found your message in Gmail spam folder.

On Tuesday, April 30, 2019 3:58:09 PM CEST Sakari Ailus wrote:
> Hi Janusz,
>
> On Mon, Apr 08, 2019 at 11:42:31PM +0200, Janusz Krzysztofik wrote:
> > Commit 717fd5b4907ad ("[media] v4l2: replace try_mbus_fmt by set_fmt")
> > converted a former ov6650_try_fmt() video operation callback to an
> > ov6650_set_fmt() pad operation callback. However, the function does not
> > verify correctness of user provided format->which flag and pad config
> > pointer arguments. Fix it.
> >
> > Fixes: 717fd5b4907ad ("[media] v4l2: replace try_mbus_fmt by set_fmt")
> > Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>
> > Cc: stable@vger.kernel.org
> > ---
> > drivers/media/i2c/ov6650.c | 11 +++++++++++
> > 1 file changed, 11 insertions(+)
> >
> > diff --git a/drivers/media/i2c/ov6650.c b/drivers/media/i2c/ov6650.c
> > index 007f0ca24913..3062c9a6c57b 100644
> > --- a/drivers/media/i2c/ov6650.c
> > +++ b/drivers/media/i2c/ov6650.c
> > @@ -679,6 +679,17 @@ static int ov6650_set_fmt(struct v4l2_subdev *sd,
> > if (format->pad)
> > return -EINVAL;
> >
> > + switch (format->which) {
> > + case V4L2_SUBDEV_FORMAT_ACTIVE:
> > + break;
> > + case V4L2_SUBDEV_FORMAT_TRY:
> > + if (cfg)
> > + break;
> > + /* fall through */
> > + default:
> > + return -EINVAL;
> > + }
>
> For this to return an error, there would need to be a problem on the
> caller's side. In other words, this isn't supposed to happen.

How about raising a bug if that happens nevertheless?

@@ -677,10 +677,20 @@ static int ov6650_set_fmt(struct v4l2_subdev *sd,
struct ov6650 *priv = to_ov6650(client);

if (format->pad)
return -EINVAL;

+ switch (format->which) {
+ case V4L2_SUBDEV_FORMAT_TRY:
+ BUG_ON(!cfg);
+ /* fall through */
+ case V4L2_SUBDEV_FORMAT_ACTIVE:
+ break;
+ default:
+ BUG();
+ }
+
if (is_unscaled_ok(mf->width, mf->height, &priv->rect))
v4l_bound_align_image(&mf->width, 2, W_CIF, 1,
&mf->height, 2, H_CIF, 1, 0);

mf->field = V4L2_FIELD_NONE;

Thanks,
Janusz

>
> Instead of adding such checks to all drivers, I think they instead should
> be added to the caller's side. The checks already exist for uAPI, but not
> for other drivers.
>
> The same applies to patches until 7th (including).
>
> > +
> > if (is_unscaled_ok(mf->width, mf->height, &priv->rect))
> > v4l_bound_align_image(&mf->width, 2, W_CIF, 1,
> > &mf->height, 2, H_CIF, 1, 0);
>
>