drm/exynos: added validation of edid for vidi connection

If edid of vidi from user is invalid, size calculated from a number
of cea extensions can be wrong. So, validation should be checked.

Changelog v2:
- just code cleanup
  . declare raw_edid only if vidi->connection is enabled.

Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>

drivers/gpu/drm/exynos/exynos_drm_vidi.c

@@ -521,7 +521,6 @@ int vidi_connection_ioctl(struct drm_device *drm_dev, void *data,
 	struct exynos_drm_manager *manager;
 	struct exynos_drm_display_ops *display_ops;
 	struct drm_exynos_vidi_connection *vidi = data;
-	struct edid *raw_edid;
 	int edid_len;
 
 	DRM_DEBUG_KMS("%s\n", __FILE__);
@@ -558,11 +557,11 @@ int vidi_connection_ioctl(struct drm_device *drm_dev, void *data,
 	}
 
 	if (vidi->connection) {
-		if (!vidi->edid) {
-			DRM_DEBUG_KMS("edid data is null.\n");
+		struct edid *raw_edid  = (struct edid *)(uint32_t)vidi->edid;
+		if (!drm_edid_is_valid(raw_edid)) {
+			DRM_DEBUG_KMS("edid data is invalid.\n");
 			return -EINVAL;
 		}
-		raw_edid = (struct edid *)(uint32_t)vidi->edid;
 		edid_len = (1 + raw_edid->extensions) * EDID_LENGTH;
 		ctx->raw_edid = kzalloc(edid_len, GFP_KERNEL);
 		if (!ctx->raw_edid) {