From 4e3578f47082c3b28be4b0065fc97e4916046d8f Mon Sep 17 00:00:00 2001
From: Sergey Sharybin <sergey.vfx@gmail.com>
Date: Fri, 23 Sep 2016 15:57:39 +0200
Subject: [PATCH] Cycles: Prevent crash in special cases when object has less
 slots than mesh

This is something what was guaranteed in give_current_material(), just
copied some range checking logic from there.

Not sure what would be a proper fix here tho.
---
 source/blender/blenkernel/intern/mesh.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/source/blender/blenkernel/intern/mesh.c b/source/blender/blenkernel/intern/mesh.c
index 7714c71681a..1cc8d8c381c 100644
--- a/source/blender/blenkernel/intern/mesh.c
+++ b/source/blender/blenkernel/intern/mesh.c
@@ -2368,8 +2368,12 @@ Mesh *BKE_mesh_new_from_object(
 			if (tmpcu->mat) {
 				for (i = tmpcu->totcol; i-- > 0; ) {
 					/* are we an object material or data based? */
-
-					tmpmesh->mat[i] = ob->matbits[i] ? ob->mat[i] : tmpcu->mat[i];
+					if (ob->matbits[i] && i >= ob->totcol) {
+						tmpmesh->mat[i] = NULL;
+					}
+					else {
+						tmpmesh->mat[i] = ob->matbits[i] ? ob->mat[i] : tmpcu->mat[i];
+					}
 
 					if (do_mat_id_us && tmpmesh->mat[i]) {
 						id_us_plus(&tmpmesh->mat[i]->id);
@@ -2388,7 +2392,12 @@ Mesh *BKE_mesh_new_from_object(
 			if (tmpmb->mat) {
 				for (i = tmpmb->totcol; i-- > 0; ) {
 					/* are we an object material or data based? */
-					tmpmesh->mat[i] = ob->matbits[i] ? ob->mat[i] : tmpmb->mat[i];
+					if (ob->matbits[i] && i >= ob->totcol) {
+						tmpmesh->mat[i] = NULL;
+					}
+					else {
+						tmpmesh->mat[i] = ob->matbits[i] ? ob->mat[i] : tmpmb->mat[i];
+					}
 
 					if (do_mat_id_us && tmpmesh->mat[i]) {
 						id_us_plus(&tmpmesh->mat[i]->id);
@@ -2408,7 +2417,12 @@ Mesh *BKE_mesh_new_from_object(
 				if (origmesh->mat) {
 					for (i = origmesh->totcol; i-- > 0; ) {
 						/* are we an object material or data based? */
-						tmpmesh->mat[i] = ob->matbits[i] ? ob->mat[i] : origmesh->mat[i];
+						if (ob->matbits[i] && i >= ob->totcol) {
+							tmpmesh->mat[i] = NULL;
+						}
+						else {
+							tmpmesh->mat[i] = ob->matbits[i] ? ob->mat[i] : origmesh->mat[i];
+						}
 
 						if (do_mat_id_us && tmpmesh->mat[i]) {
 							id_us_plus(&tmpmesh->mat[i]->id);