On Fri, Aug 21, 2020 at 12:12:28PM +0200, Hans Verkuil wrote:
> Arrgh! I know what this is. /dev/video6 corresponds to the Metadata output
> device of vivid, and that metadata format sets brightness, contrast,
> saturation and hue:
>
> struct vivid_meta_out_buf {
> u16 brightness;
> u16 contrast;
> u16 saturation;
> s16 hue;
> };
>
> vivid_meta_out_process() calls tpg_s_* functions to set these values. But
> this is wrong, it should set the corresponding V4L2 controls instead since
> calling these tpg_s_* functions bypasses all range checks. It also will
> not update the controls themselves, so they are out-of-sync with the actual
> values. I.e. the test pattern generator uses different values compared to
> the values in the controls.
>
> So two patches are needed:
>
> 1) a patch for include/media/tpg/v4l2-tpg.h where tpg_s_hue will clamp the
> hue value to the valid range. This to prevent anyone else from setting invalid
> hue values in the tpg.
>
> 2) a patch for drivers/media/test-drivers/vivid/vivid-meta-out.c where,
> instead of calling the tpg_s_* functions in vivid_meta_out_process(), it
> calls instead:
>
> v4l2_ctrl_s_ctrl(dev->brightness, meta->brightness);
> v4l2_ctrl_s_ctrl(dev->contrast, meta->contrast);
> etc.
>
> Do patch 2 first and test with syzkaller to check that by going through the
> controls this issue is resolved. Since with that approach the tpg should
> always get valid hue values.
Ah, now it all makes sense! Thank you! I will do them now.
Peilin
