[PATCH 4.8 105/138] drm/imx: ipuv3-plane: Access old u/vbo properly in ->atomic_check for YU12/YV12

[Greg Kroah-Hartman]

4.8-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Liu Ying <gnuiyl@xxxxxxxxx>

commit e73aca5184ad9fc948ba22b4d35dce11db35bb25 upstream.

Before accessing the u/v offset(aka, u/vbo for IPUv3) of the old plane state's
relevant fb, we should make sure the fb is in YU12 or YV12 pixel format(which
are the two YUV pixel formats we support only), otherwise, we are likely to
trigger BUG_ON() in drm_plane_state_to_u/vbo() since the fb's pixel format is
probably not YU12 or YV12.

Link: https://bugs.freedesktop.org/show_bug.cgi?id=98150
Fixes: c6c1f9bc798b ("drm/imx: Add active plane reconfiguration support")
Signed-off-by: Liu Ying <gnuiyl@xxxxxxxxx>
Signed-off-by: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/gpu/drm/imx/ipuv3-plane.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/imx/ipuv3-plane.c
+++ b/drivers/gpu/drm/imx/ipuv3-plane.c
@@ -360,7 +360,9 @@ static int ipu_plane_atomic_check(struct
 		if ((ubo > 0xfffff8) || (vbo > 0xfffff8))
 			return -EINVAL;
 
-		if (old_fb) {
+		if (old_fb &&
+		    (old_fb->pixel_format == DRM_FORMAT_YUV420 ||
+		     old_fb->pixel_format == DRM_FORMAT_YVU420)) {
 			old_ubo = drm_plane_state_to_ubo(old_state);
 			old_vbo = drm_plane_state_to_vbo(old_state);
 			if (ubo != old_ubo || vbo != old_vbo)