diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index 2ce80ed55b083051d83c0888f09867b3a34f6057..d7a8370e3cdc4a5881e3c1b28ba74d089f18a8fc 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -1319,6 +1319,9 @@ static int drm_crtc_convert_umode(struct drm_display_mode *out,
 	if (in->clock > INT_MAX || in->vrefresh > INT_MAX)
 		return -ERANGE;
 
+	if ((in->flags & DRM_MODE_FLAG_3D_MASK) > DRM_MODE_FLAG_3D_MAX)
+		return -EINVAL;
+
 	out->clock = in->clock;
 	out->hdisplay = in->hdisplay;
 	out->hsync_start = in->hsync_start;
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index eb6b8dc971d9519ba250be88b26d7399a6ec1afe..50cedadc9fcc05c33a209ffd19be4be440233c23 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -128,6 +128,8 @@ enum drm_mode_status {
 #define CRTC_INTERLACE_HALVE_V	(1 << 0) /* halve V values for interlacing */
 #define CRTC_STEREO_DOUBLE	(1 << 1) /* adjust timings for stereo modes */
 
+#define DRM_MODE_FLAG_3D_MAX	DRM_MODE_FLAG_3D_SIDE_BY_SIDE_HALF
+
 struct drm_display_mode {
 	/* Header */
 	struct list_head head;
diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
index 7980f89940700b190df28f147ed8d03d58263a08..c2c4ace3db610abc481240031a396ca76eabcaec 100644
--- a/include/uapi/drm/drm_mode.h
+++ b/include/uapi/drm/drm_mode.h
@@ -58,6 +58,10 @@
 #define DRM_MODE_FLAG_PIXMUX			(1<<11)
 #define DRM_MODE_FLAG_DBLCLK			(1<<12)
 #define DRM_MODE_FLAG_CLKDIV2			(1<<13)
+ /*
+  * When adding a new stereo mode don't forget to adjust DRM_MODE_FLAGS_3D_MAX
+  * (define not exposed to user space).
+  */
 #define DRM_MODE_FLAG_3D_MASK			(0x1f<<14)
 #define  DRM_MODE_FLAG_3D_NONE			(0<<14)
 #define  DRM_MODE_FLAG_3D_FRAME_PACKING		(1<<14)