Merge pull request #2728 from govm/fix-dereference-invalid-argv

fix pointer dereference after realloc

src/vm.c

@@ -340,6 +340,7 @@ mrb_funcall_with_block(mrb_state *mrb, mrb_value self, mrb_sym mid, mrb_int argc
     mrb_sym undef = 0;
     mrb_callinfo *ci;
     int n;
+    ptrdiff_t voff = -1;
 
     if (!mrb->c->stack) {
       stack_init(mrb);
@@ -363,6 +364,9 @@ mrb_funcall_with_block(mrb_state *mrb, mrb_value self, mrb_sym mid, mrb_int argc
     ci->argc = argc;
     ci->target_class = c;
     mrb->c->stack = mrb->c->stack + n;
+    if (mrb->c->stbase <= argv && argv < mrb->c->stend) {
+      voff = argv - mrb->c->stbase;
+    }
     if (MRB_PROC_CFUNC_P(p)) {
       ci->nregs = argc + 2;
       stack_extend(mrb, ci->nregs, 0);
@@ -371,6 +375,9 @@ mrb_funcall_with_block(mrb_state *mrb, mrb_value self, mrb_sym mid, mrb_int argc
       ci->nregs = p->body.irep->nregs + n;
       stack_extend(mrb, ci->nregs, argc+2);
     }
+    if (voff >= 0) {
+      argv = mrb->c->stbase + voff;
+    }
     mrb->c->stack[0] = self;
     if (undef) {
       mrb->c->stack[1] = mrb_symbol_value(undef);