Re: [gnugo-devel] 3.3.12: array bound violation in surround.c

[Gunnar Farneback]

Teun wrote:
> Array bounds checking revealed an array bound violation in surround.c
> line 265
> It is fixed by this patch
> 
> - enlarge mn array in surround.c to avoid array bound violation.

Unfortunately the patch trades a (mostly) harmless array bound
violation for a definitive memory corruption on line 382.

The patch below should be safer.

/Gunnar

Index: engine/surround.c
===================================================================
RCS file: /cvsroot/gnugo/gnugo/engine/surround.c,v
retrieving revision 1.3
diff -u -r1.3 surround.c
--- engine/surround.c   18 Nov 2002 06:03:52 -0000      1.3
+++ engine/surround.c   22 Nov 2002 17:49:12 -0000
@@ -261,10 +261,10 @@
   /* mark the expanded region */
 
   for (dpos = BOARDMIN; dpos < BOARDMAX; dpos++)
-    if (ON_BOARD(dpos) && !mn[dpos] && 
-       ((mn[NORTH(dpos)]==1) || (mn[SOUTH(dpos)]==1)
-        || (mn[EAST(dpos)]==1) || (mn[WEST(dpos)]==1)))
-      mn[dpos] = 2;
+    if (ON_BOARD(dpos) && mn[dpos] == 1)
+      for (k = 0; k < 4; k++)
+       if (ON_BOARD(dpos + delta[k]) && !mn[dpos + delta[k]])
+         mn[dpos + delta[k]] = 2;
       
   /* Mark allied dragons that intersect the (unexpanded) hull.
    * These must all lie entirely within the hull for the