[Bf-blender-cvs] [b00822e] blender-v2.77-release: Fix T47644: crash (use-after-free) regression from rB7a74738914a66e.

[Bastien Montagne]

Commit: b00822e42dc822b90ccb7c44ca263af294f68944
Author: Bastien Montagne
Date:   Thu Mar 3 14:44:05 2016 +0100
Branches: blender-v2.77-release
https://developer.blender.org/rBb00822e42dc822b90ccb7c44ca263af294f68944

Fix T47644: crash (use-after-free) regression from rB7a74738914a66e.

Handling `me` data here is not good idea anyway, we override it completly with data
from `tmp` (crash came from freeing already existing bb from me, while pointer still existed in tmp).

(rediscovered it while working on T47676...).

To be backported to 2.77.

===================================================================

M	source/blender/blenkernel/intern/DerivedMesh.c

===================================================================

diff --git a/source/blender/blenkernel/intern/DerivedMesh.c b/source/blender/blenkernel/intern/DerivedMesh.c
index fa9875e..423e897 100644
--- a/source/blender/blenkernel/intern/DerivedMesh.c
+++ b/source/blender/blenkernel/intern/DerivedMesh.c
@@ -808,13 +808,12 @@ void DM_to_mesh(DerivedMesh *dm, Mesh *me, Object *ob, CustomDataMask mask, bool
 	}
 
 	/* Clear selection history */
-	tmp.mselect = NULL;
+	MEM_SAFE_FREE(tmp.mselect);
 	tmp.totselect = 0;
-	if (me->mselect) {
-		MEM_freeN(me->mselect);
-	}
+	BLI_assert(ELEM(tmp.bb, NULL, me->bb));
 	if (me->bb) {
 		MEM_freeN(me->bb);
+		tmp.bb = NULL;
 	}
 
 	/* skip the listbase */