ko1	2018-10-19 14:26:35 +0900 (Fri, 19 Oct 2018)

  New Revision: 65162

  https://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=65162

  Log:
    check before access.
    
    * vm_insnhelper.c (vm_push_frame): validate prev_frame because
      prev_frame can be the end of frame.

  Modified files:
    trunk/vm_insnhelper.c
Index: vm_insnhelper.c
===================================================================
--- vm_insnhelper.c	(revision 65161)
+++ vm_insnhelper.c	(revision 65162)
@@ -271,9 +271,10 @@ vm_push_frame(rb_execution_context_t *ec https://github.com/ruby/ruby/blob/trunk/vm_insnhelper.c#L271
     }
     {
         rb_control_frame_t *prev_cfp = RUBY_VM_PREVIOUS_CONTROL_FRAME(cfp);
-        int cur_ruby_frame = VM_FRAME_RUBYFRAME_P(cfp);
-        int pre_ruby_frame = VM_FRAME_RUBYFRAME_P(prev_cfp);
         if (RUBY_VM_END_CONTROL_FRAME(ec) != prev_cfp) {
+            int cur_ruby_frame = VM_FRAME_RUBYFRAME_P(cfp);
+            int pre_ruby_frame = VM_FRAME_RUBYFRAME_P(prev_cfp);
+
             pre_ruby_frame ? (cur_ruby_frame ? RB_DEBUG_COUNTER_INC(frame_R2R) :
                                                RB_DEBUG_COUNTER_INC(frame_R2C)):
                              (cur_ruby_frame ? RB_DEBUG_COUNTER_INC(frame_C2R) :

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