[media] s5k6aa: Fix possible NULL pointer dereference

Make sure __s5k6aa_get_crop_rect() always returns valid pointer,
as it is assumed at the callers.
crop->which is already validated when subdev set_crop and get_crop
callbacks are called from within the v4l2-core. If it ever happens
the crop operations are called directly for some reason in kernel
space, with incorrect crop->which argument, just log it with WARN
and return reference to the TRY crop.

Reported-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Acked-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/i2c/s5k6aa.c

@@ -1061,10 +1061,9 @@ __s5k6aa_get_crop_rect(struct s5k6aa *s5k6aa, struct v4l2_subdev_fh *fh,
 {
 	if (which == V4L2_SUBDEV_FORMAT_ACTIVE)
 		return &s5k6aa->ccd_rect;
-	if (which == V4L2_SUBDEV_FORMAT_TRY)
-		return v4l2_subdev_get_try_crop(fh, 0);
 
-	return NULL;
+	WARN_ON(which != V4L2_SUBDEV_FORMAT_TRY);
+	return v4l2_subdev_get_try_crop(fh, 0);
 }
 
 static void s5k6aa_try_format(struct s5k6aa *s5k6aa,
@@ -1169,12 +1168,10 @@ static int s5k6aa_get_crop(struct v4l2_subdev *sd, struct v4l2_subdev_fh *fh,
 	struct v4l2_rect *rect;
 
 	memset(crop->reserved, 0, sizeof(crop->reserved));
-	mutex_lock(&s5k6aa->lock);
 
+	mutex_lock(&s5k6aa->lock);
 	rect = __s5k6aa_get_crop_rect(s5k6aa, fh, crop->which);
-	if (rect)
-		crop->rect = *rect;
-
+	crop->rect = *rect;
 	mutex_unlock(&s5k6aa->lock);
 
 	v4l2_dbg(1, debug, sd, "Current crop rectangle: (%d,%d)/%dx%d\n",