ipu3-imgu: Fix NULL pointer dereference in imgu_subdev_set_selection()

Calling v4l2_subdev_get_try_crop() and v4l2_subdev_get_try_compose()
with a subdev state of NULL leads to a NULL pointer dereference. This
can currently happen in imgu_subdev_set_selection() when the state
passed in is NULL, as this method first gets pointers to both the "try"
and "active" states and only then decides which to use.

The same issue has been addressed for imgu_subdev_get_selection() with
commit 30d03a0de650 ("ipu3-imgu: Fix NULL pointer dereference in active
selection access"). However the issue still persists in
imgu_subdev_set_selection().

Therefore, apply a similar fix as done in the aforementioned commit to
imgu_subdev_set_selection(). To keep things a bit cleaner, introduce
helper functions for "crop" and "compose" access and use them in both
imgu_subdev_set_selection() and imgu_subdev_get_selection().

Fixes: 0d346d2a ("media: v4l2-subdev: add subdev-wide state struct")
Cc: stable@vger.kernel.org # for v5.14 and later
Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>

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

@@ -188,6 +188,28 @@ static int imgu_subdev_set_fmt(struct v4l2_subdev *sd,
 	return 0;
 }
 
+static struct v4l2_rect *
+imgu_subdev_get_crop(struct imgu_v4l2_subdev *sd,
+		     struct v4l2_subdev_state *sd_state, unsigned int pad,
+		     enum v4l2_subdev_format_whence which)
+{
+	if (which == V4L2_SUBDEV_FORMAT_TRY)
+		return v4l2_subdev_get_try_crop(&sd->subdev, sd_state, pad);
+	else
+		return &sd->rect.eff;
+}
+
+static struct v4l2_rect *
+imgu_subdev_get_compose(struct imgu_v4l2_subdev *sd,
+			struct v4l2_subdev_state *sd_state, unsigned int pad,
+			enum v4l2_subdev_format_whence which)
+{
+	if (which == V4L2_SUBDEV_FORMAT_TRY)
+		return v4l2_subdev_get_try_compose(&sd->subdev, sd_state, pad);
+	else
+		return &sd->rect.bds;
+}
+
 static int imgu_subdev_get_selection(struct v4l2_subdev *sd,
 				     struct v4l2_subdev_state *sd_state,
 				     struct v4l2_subdev_selection *sel)
@@ -200,18 +222,12 @@ static int imgu_subdev_get_selection(struct v4l2_subdev *sd,
 
 	switch (sel->target) {
 	case V4L2_SEL_TGT_CROP:
-		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;
+		sel->r = *imgu_subdev_get_crop(imgu_sd, sd_state, sel->pad,
+					       sel->which);
 		return 0;
 	case V4L2_SEL_TGT_COMPOSE:
-		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;
+		sel->r = *imgu_subdev_get_compose(imgu_sd, sd_state, sel->pad,
+						  sel->which);
 		return 0;
 	default:
 		return -EINVAL;
@@ -223,10 +239,9 @@ static int imgu_subdev_set_selection(struct v4l2_subdev *sd,
 				     struct v4l2_subdev_selection *sel)
 {
 	struct imgu_device *imgu = v4l2_get_subdevdata(sd);
-	struct imgu_v4l2_subdev *imgu_sd = container_of(sd,
-							struct imgu_v4l2_subdev,
-							subdev);
-	struct v4l2_rect *rect, *try_sel;
+	struct imgu_v4l2_subdev *imgu_sd =
+		container_of(sd, struct imgu_v4l2_subdev, subdev);
+	struct v4l2_rect *rect;
 
 	dev_dbg(&imgu->pci_dev->dev,
 		 "set subdev %u sel which %u target 0x%4x rect [%ux%u]",
@@ -238,22 +253,18 @@ static int imgu_subdev_set_selection(struct v4l2_subdev *sd,
 
 	switch (sel->target) {
 	case V4L2_SEL_TGT_CROP:
-		try_sel = v4l2_subdev_get_try_crop(sd, sd_state, sel->pad);
-		rect = &imgu_sd->rect.eff;
+		rect = imgu_subdev_get_crop(imgu_sd, sd_state, sel->pad,
+					    sel->which);
 		break;
 	case V4L2_SEL_TGT_COMPOSE:
-		try_sel = v4l2_subdev_get_try_compose(sd, sd_state, sel->pad);
-		rect = &imgu_sd->rect.bds;
+		rect = imgu_subdev_get_compose(imgu_sd, sd_state, sel->pad,
+					       sel->which);
 		break;
 	default:
 		return -EINVAL;
 	}
 
-	if (sel->which == V4L2_SUBDEV_FORMAT_TRY)
-		*try_sel = sel->r;
-	else
-		*rect = sel->r;
-
+	*rect = sel->r;
 	return 0;
 }