Dungeongen: Fix out-of-voxelmanip access segfault

My recent dungeon commit allowed stairs to be placed across the full width of corridors, but some of the new node positions accessed were missing checks for being within the voxelmanip, causing occasional segfaults near dungeons with corridors wider than 1 node. Add 'vm->m_area.contains(pos)' checks just before stair position voxelmanip access. This allows an earlier check to be removed as it is now redundant.
minetest · Jan 25, 2017 · 9f108b5 · 9f108b5
1 parent 0891116
commit 9f108b5
Showing 1 changed file with 6 additions and 4 deletions.
diff --git a/src/dungeongen.cpp b/src/dungeongen.cpp
@@ -415,8 +415,8 @@ void DungeonGen::makeCorridor(v3s16 doorplace, v3s16 doordir,
 		if (partcount != 0)
 			p.Y += make_stairs;
 
-		if (vm->m_area.contains(p) && vm->m_area.contains(p + v3s16(0, 1, 0)) &&
-				vm->m_area.contains(v3s16(p.X - dir.X, p.Y - 1, p.Z - dir.Z))) {
+		// Check segment of minimum size corridor is in voxelmanip
+		if (vm->m_area.contains(p) && vm->m_area.contains(p + v3s16(0, 1, 0))) {
 			if (make_stairs) {
 				makeFill(p + v3s16(-1, -1, -1),
 					dp.holesize + v3s16(2, 3, 2),
@@ -444,11 +444,13 @@ void DungeonGen::makeCorridor(v3s16 doorplace, v3s16 doordir,
 
 					for (u16 st = 0; st < stair_width; st++) {
 						u32 vi = vm->m_area.index(ps.X - dir.X, ps.Y - 1, ps.Z - dir.Z);
-						if (vm->m_data[vi].getContent() == dp.c_wall)
+						if (vm->m_area.contains(ps + v3s16(-dir.X, -1, -dir.Z)) &&
+								vm->m_data[vi].getContent() == dp.c_wall)
 							vm->m_data[vi] = MapNode(dp.c_stair, 0, facedir);
 
 						vi = vm->m_area.index(ps.X, ps.Y, ps.Z);
-						if (vm->m_data[vi].getContent() == dp.c_wall)
+						if (vm->m_area.contains(ps) &&
+								vm->m_data[vi].getContent() == dp.c_wall)
 							vm->m_data[vi] = MapNode(dp.c_stair, 0, facedir);
 
 						ps += swv;