media: ipu3-imgu: Fix NULL pointer dereference in active selection access

What the IMGU driver did was that it first acquired the pointers to active
and try V4L2 subdev state, and only then figured out which one to use.

The problem with that approach and a later patch (see Fixes: tag) is that
as sd_state argument to v4l2_subdev_get_try_crop() et al is NULL, there is
now an attempt to dereference that.

Fix this.

Also rewrap lines a little.

Fixes: 0d346d2a ("media: v4l2-subdev: add subdev-wide state struct")
Cc: stable@vger.kernel.org # for v5.14 and later
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: Bingbu Cao <bingbu.cao@intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

drivers/staging/media/ipu3/ipu3-v4l2.c

@@ -192,33 +192,30 @@ static int imgu_subdev_get_selection(struct v4l2_subdev *sd,
 				     struct v4l2_subdev_state *sd_state,
 				     struct v4l2_subdev_selection *sel)
 {
-	struct v4l2_rect *try_sel, *r;
-	struct imgu_v4l2_subdev *imgu_sd = container_of(sd,
-							struct imgu_v4l2_subdev,
-							subdev);
+	struct imgu_v4l2_subdev *imgu_sd =
+		container_of(sd, struct imgu_v4l2_subdev, subdev);
 
 	if (sel->pad != IMGU_NODE_IN)
 		return -EINVAL;
 
 	switch (sel->target) {
 	case V4L2_SEL_TGT_CROP:
-		try_sel = v4l2_subdev_get_try_crop(sd, sd_state, sel->pad);
-		r = &imgu_sd->rect.eff;
-		break;
+		if (sel->which == V4L2_SUBDEV_FORMAT_TRY)
+			sel->r = *v4l2_subdev_get_try_crop(sd, sd_state,
+							   sel->pad);
+		else
+			sel->r = imgu_sd->rect.eff;
+		return 0;
 	case V4L2_SEL_TGT_COMPOSE:
-		try_sel = v4l2_subdev_get_try_compose(sd, sd_state, sel->pad);
-		r = &imgu_sd->rect.bds;
-		break;
+		if (sel->which == V4L2_SUBDEV_FORMAT_TRY)
+			sel->r = *v4l2_subdev_get_try_compose(sd, sd_state,
+							      sel->pad);
+		else
+			sel->r = imgu_sd->rect.bds;
+		return 0;
 	default:
 		return -EINVAL;
 	}
-
-	if (sel->which == V4L2_SUBDEV_FORMAT_TRY)
-		sel->r = *try_sel;
-	else
-		sel->r = *r;
-
-	return 0;
 }
 
 static int imgu_subdev_set_selection(struct v4l2_subdev *sd,