drm/tilcdc: fix leak & null ref in panel_connector_get_modes

BugLink: https://bugs.launchpad.net/bugs/1892822

[ Upstream commit 3f9c1c87 ]

If videomode_from_timings() returns true, the mode allocated with
drm_mode_create will be leaked.

Also, the return value of drm_mode_create() is never checked, and thus
could cause NULL deref.

Fix these two issues.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200429104234.18910-1-tomi.valkeinen@ti.comReviewed-by: Jyri Sarha <jsarha@ti.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
Signed-off-by: Ian May <ian.may@canonical.com>
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>

drivers/gpu/drm/tilcdc/tilcdc_panel.c

@@ -177,12 +177,16 @@ static int panel_connector_get_modes(struct drm_connector *connector)
 	int i;
 
 	for (i = 0; i < timings->num_timings; i++) {
-		struct drm_display_mode *mode = drm_mode_create(dev);
+		struct drm_display_mode *mode;
 		struct videomode vm;
 
 		if (videomode_from_timings(timings, &vm, i))
 			break;
 
+		mode = drm_mode_create(dev);
+		if (!mode)
+			break;
+
 		drm_display_mode_from_videomode(&vm, mode);
 
 		mode->type = DRM_MODE_TYPE_DRIVER;