drm/uapi: Validate the mode flags/type

Currently userspace is allowed to feed in any king of garbage in the
high bits of the mode flags/type, as are drivers when probing modes.
Reject any mode with bogus flags/type.

Hopefully this won't break any current userspace...

v2: Split the type and flags checks to separates ifs (Chris)

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jose Abreu <Jose.Abreu@synopsys.com>
Cc: Adam Jackson <ajax@redhat.com>
Cc: Keith Packard <keithp@keithp.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171115154913.23827-1-ville.syrjala@linux.intel.com
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/drm_modes.c

@@ -1036,6 +1036,12 @@ EXPORT_SYMBOL(drm_mode_equal_no_clocks_no_stereo);
 enum drm_mode_status
 drm_mode_validate_basic(const struct drm_display_mode *mode)
 {
+	if (mode->type & ~DRM_MODE_TYPE_ALL)
+		return MODE_BAD;
+
+	if (mode->flags & ~DRM_MODE_FLAG_ALL)
+		return MODE_BAD;
+
 	if ((mode->flags & DRM_MODE_FLAG_3D_MASK) > DRM_MODE_FLAG_3D_MAX)
 		return MODE_BAD;
 

include/uapi/drm/drm_mode.h

@@ -46,6 +46,14 @@ extern "C" {
 #define DRM_MODE_TYPE_USERDEF	(1<<5)
 #define DRM_MODE_TYPE_DRIVER	(1<<6)
 
+#define DRM_MODE_TYPE_ALL	(DRM_MODE_TYPE_BUILTIN |	\
+				 DRM_MODE_TYPE_CLOCK_C |	\
+				 DRM_MODE_TYPE_CRTC_C |		\
+				 DRM_MODE_TYPE_PREFERRED |	\
+				 DRM_MODE_TYPE_DEFAULT |	\
+				 DRM_MODE_TYPE_USERDEF |	\
+				 DRM_MODE_TYPE_DRIVER)
+
 /* Video mode flags */
 /* bit compatible with the xrandr RR_ definitions (bits 0-13)
  *
@@ -99,6 +107,22 @@ extern "C" {
 #define  DRM_MODE_FLAG_PIC_AR_16_9 \
 			(DRM_MODE_PICTURE_ASPECT_16_9<<19)
 
+#define  DRM_MODE_FLAG_ALL	(DRM_MODE_FLAG_PHSYNC |		\
+				 DRM_MODE_FLAG_NHSYNC |		\
+				 DRM_MODE_FLAG_PVSYNC |		\
+				 DRM_MODE_FLAG_NVSYNC |		\
+				 DRM_MODE_FLAG_INTERLACE |	\
+				 DRM_MODE_FLAG_DBLSCAN |	\
+				 DRM_MODE_FLAG_CSYNC |		\
+				 DRM_MODE_FLAG_PCSYNC |		\
+				 DRM_MODE_FLAG_NCSYNC |		\
+				 DRM_MODE_FLAG_HSKEW |		\
+				 DRM_MODE_FLAG_BCAST |		\
+				 DRM_MODE_FLAG_PIXMUX |		\
+				 DRM_MODE_FLAG_DBLCLK |		\
+				 DRM_MODE_FLAG_CLKDIV2 |	\
+				 DRM_MODE_FLAG_3D_MASK)
+
 /* DPMS flags */
 /* bit compatible with the xorg definitions. */
 #define DRM_MODE_DPMS_ON	0