Em Mon, 9 Oct 2017 23:23:56 +0300
Sakari Ailus <sakari.ailus@xxxxxx> escreveu:
> Hi Mauro,
>
> On Mon, Oct 09, 2017 at 07:19:21AM -0300, Mauro Carvalho Chehab wrote:
> > The __V4L2_SUBDEV_MK_GET_TRY() macro is used to define
> > 3 functions that have the same arguments. The code of those
> > functions is simple enough to just declare them, de-obfuscating
> > the code.
> >
> > While here, replace BUG_ON() by WARN_ON() as there's no reason
> > why to panic the Kernel if this fails.
>
> BUG_ON() might actually be a better idea as this will lead to memory
> corruption. I presume it's not been hit often.
Well, let's then change the code to:
if (WARN_ON(pad >= sd->entity.num_pads))
return -EINVAL;
This way, it won't try to use an invalid value. As those are default
handlers for ioctls, userspace should be able to handle it.
>
> That said, I, too, favour WARN_ON() in this case. In case pad exceeds the
> number of pads, then zero could be used, for instance. The only real
> problem comes if there were no pads to begin with. The callers of these
> functions also don't expect to receive NULL. Another option would be to
> define a static, dummy variable for the purpose that would be at least safe
> to access. Or we could just use the dummy entry whenever the pad isn't
> valid.
>
> This will make the functions more complex and I might just keep the
> original macro. Even grep works on it nowadays.
>
> >
> > Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxxx>
> > ---
> > include/media/v4l2-subdev.h | 37 +++++++++++++++++++++++++------------
> > 1 file changed, 25 insertions(+), 12 deletions(-)
> >
> > diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
> > index 1f34045f07ce..35c4476c56ee 100644
> > --- a/include/media/v4l2-subdev.h
> > +++ b/include/media/v4l2-subdev.h
> > @@ -897,19 +897,32 @@ struct v4l2_subdev_fh {
> > container_of(fh, struct v4l2_subdev_fh, vfh)
> >
> > #if defined(CONFIG_VIDEO_V4L2_SUBDEV_API)
> > -#define __V4L2_SUBDEV_MK_GET_TRY(rtype, fun_name, field_name) \
> > - static inline struct rtype * \
> > - fun_name(struct v4l2_subdev *sd, \
> > - struct v4l2_subdev_pad_config *cfg, \
> > - unsigned int pad) \
> > - { \
> > - BUG_ON(pad >= sd->entity.num_pads); \
> > - return &cfg[pad].field_name; \
> > - }
> > +static inline struct v4l2_mbus_framefmt
> > +*v4l2_subdev_get_try_format(struct v4l2_subdev *sd,
> > + struct v4l2_subdev_pad_config *cfg,
> > + unsigned int pad)
> > +{
> > + WARN_ON(pad >= sd->entity.num_pads);
> > + return &cfg[pad].try_fmt;
> > +}
> >
> > -__V4L2_SUBDEV_MK_GET_TRY(v4l2_mbus_framefmt, v4l2_subdev_get_try_format, try_fmt)
> > -__V4L2_SUBDEV_MK_GET_TRY(v4l2_rect, v4l2_subdev_get_try_crop, try_crop)
> > -__V4L2_SUBDEV_MK_GET_TRY(v4l2_rect, v4l2_subdev_get_try_compose, try_compose)
> > +static inline struct v4l2_rect
> > +*v4l2_subdev_get_try_crop(struct v4l2_subdev *sd,
> > + struct v4l2_subdev_pad_config *cfg,
> > + unsigned int pad)
> > +{
> > + WARN_ON(pad >= sd->entity.num_pads);
> > + return &cfg[pad].try_crop;
> > +}
> > +
> > +static inline struct v4l2_rect
> > +*v4l2_subdev_get_try_compose(struct v4l2_subdev *sd,
> > + struct v4l2_subdev_pad_config *cfg,
> > + unsigned int pad)
> > +{
> > + WARN_ON(pad >= sd->entity.num_pads);
> > + return &cfg[pad].try_compose;
> > +}
> > #endif
> >
> > extern const struct v4l2_file_operations v4l2_subdev_fops;
>
Thanks,
Mauro
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