From bec074e6a31fd7a577e2c0e726167da8dc44c4c6 Mon Sep 17 00:00:00 2001
From: "Yukihiro \"Matz\" Matsumoto" <matz@ruby.or.jp>
Date: Fri, 8 Oct 2021 15:31:37 +0900
Subject: [PATCH] vm.c: check call stack depth before pushing the frame.

Existing call stack depth checks are unified into this check in
`cipush()`. The maximum depth is now specified by `MRB_CALL_LEVEL_MAX`
(the default is 512).  The older `MRB_FUNCALL_DEPTH_MAX` is no longer
used.
---
 src/vm.c | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/src/vm.c b/src/vm.c
index f3332353b6..69a8732813 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -39,9 +39,9 @@ void abort(void);
 #define MRB_STACK_GROWTH 128
 #endif
 
-/* Maximum mrb_funcall() depth. Should be set lower on memory constrained systems. */
-#ifndef MRB_FUNCALL_DEPTH_MAX
-#define MRB_FUNCALL_DEPTH_MAX 512
+/* Maximum recursive depth. Should be set lower on memory constrained systems. */
+#ifndef MRB_CALL_LEVEL_MAX
+#define MRB_CALL_LEVEL_MAX 512
 #endif
 
 /* Maximum stack depth. Should be set lower on memory constrained systems.
@@ -251,6 +251,9 @@ cipush(mrb_state *mrb, mrb_int push_stacks, uint8_t cci,
   if (ci + 1 == c->ciend) {
     ptrdiff_t size = ci - c->cibase;
 
+    if (size > MRB_CALL_LEVEL_MAX) {
+      mrb_exc_raise(mrb, mrb_obj_value(mrb->stack_err));
+    }
     c->cibase = (mrb_callinfo *)mrb_realloc(mrb, c->cibase, sizeof(mrb_callinfo)*size*2);
     c->ci = c->cibase + size;
     c->ciend = c->cibase + size * 2;
@@ -464,9 +467,6 @@ mrb_funcall_with_block(mrb_state *mrb, mrb_value self, mrb_sym mid, mrb_int argc
       mrb->c->ci->stack[n+1] = args;
       argc = -1;
     }
-    if (mrb->c->ci - mrb->c->cibase > MRB_FUNCALL_DEPTH_MAX) {
-      mrb_exc_raise(mrb, mrb_obj_value(mrb->stack_err));
-    }
     ci = cipush(mrb, n, 0, c, NULL, mid, argc);
     if (argc < 0) argc = 1;
     if (mrb->c->stbase <= argv && argv < mrb->c->stend) {
@@ -740,9 +740,6 @@ mrb_yield_with_class(mrb_state *mrb, mrb_value b, mrb_int argc, const mrb_value
   }
   ci = mrb->c->ci;
   n = ci_nregs(ci);
-  if (ci - mrb->c->cibase > MRB_FUNCALL_DEPTH_MAX) {
-    mrb_exc_raise(mrb, mrb_obj_value(mrb->stack_err));
-  }
   p = mrb_proc_ptr(b);
   ci = cipush(mrb, n, CINFO_SKIP, c, p, mid, 0 /* dummy */);
   if (argc >= CALL_MAXARGS) {