[cff] Check rcurveline and rlinecurve arguments

Make sure the number of arguments is not too many or too few, otherwise
skip the command.

src/hb-cff-interp-cs-common.hh

@@ -551,8 +551,13 @@ struct path_procs_t
 
   static void rcurveline (ENV &env, PARAM& param)
   {
+    unsigned int arg_count = env.argStack.get_count ();
+    if (unlikely (arg_count < 8))
+      return;
+
     unsigned int i = 0;
-    for (; i + 6 <= env.argStack.get_count (); i += 6)
+    unsigned int curve_limit = arg_count - 2;
+    for (; i + 6 <= curve_limit; i += 6)
     {
       point_t pt1 = env.get_pt ();
       pt1.move (env.eval_arg (i), env.eval_arg (i+1));
@@ -562,34 +567,34 @@ struct path_procs_t
       pt3.move (env.eval_arg (i+4), env.eval_arg (i+5));
       PATH::curve (env, param, pt1, pt2, pt3);
     }
-    for (; i + 2 <= env.argStack.get_count (); i += 2)
-    {
-      point_t pt1 = env.get_pt ();
-      pt1.move (env.eval_arg (i), env.eval_arg (i+1));
-      PATH::line (env, param, pt1);
-    }
+
+    point_t pt1 = env.get_pt ();
+    pt1.move (env.eval_arg (i), env.eval_arg (i+1));
+    PATH::line (env, param, pt1);
   }
 
   static void rlinecurve (ENV &env, PARAM& param)
   {
+    unsigned int arg_count = env.argStack.get_count ();
+    if (unlikely (arg_count < 8))
+      return;
+
     unsigned int i = 0;
-    unsigned int line_limit = (env.argStack.get_count () - 6);
+    unsigned int line_limit = arg_count - 6;
     for (; i + 2 <= line_limit; i += 2)
     {
       point_t pt1 = env.get_pt ();
       pt1.move (env.eval_arg (i), env.eval_arg (i+1));
       PATH::line (env, param, pt1);
     }
-    for (; i + 6 <= env.argStack.get_count (); i += 6)
-    {
-      point_t pt1 = env.get_pt ();
-      pt1.move (env.eval_arg (i), env.eval_arg (i+1));
-      point_t pt2 = pt1;
-      pt2.move (env.eval_arg (i+2), env.eval_arg (i+3));
-      point_t pt3 = pt2;
-      pt3.move (env.eval_arg (i+4), env.eval_arg (i+5));
-      PATH::curve (env, param, pt1, pt2, pt3);
-    }
+
+    point_t pt1 = env.get_pt ();
+    pt1.move (env.eval_arg (i), env.eval_arg (i+1));
+    point_t pt2 = pt1;
+    pt2.move (env.eval_arg (i+2), env.eval_arg (i+3));
+    point_t pt3 = pt2;
+    pt3.move (env.eval_arg (i+4), env.eval_arg (i+5));
+    PATH::curve (env, param, pt1, pt2, pt3);
   }
 
   static void vvcurveto (ENV &env, PARAM& param)