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Crash after calling Kernel.initialize #3397

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clayton-shopify opened this Issue Jan 11, 2017 · 0 comments

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clayton-shopify commented Jan 11, 2017

The following input demonstrates a crash:

loop do
  Kernel.initialize
  [0].to_s
end

This issue was reported by https://hackerone.com/icanthack

I did some digging, and it appears the problem occurs because Kernel.initialize invokes mrb_mod_initialize, which calls boot_initmod. Then boot_initmod overwrites mod->mt if it already exists, which I suspect is causing a failure later on:

mod->mt = kh_init(mt, mrb);

The following patch checks whether mod->mt is already initialized, which appears to resolve the problem:

diff --git a/src/class.c b/src/class.c
index cb7bdfd..45827f5 100644
--- a/src/class.c
+++ b/src/class.c
@@ -915,7 +915,9 @@ boot_defclass(mrb_state *mrb, struct RClass *super)
 static void
 boot_initmod(mrb_state *mrb, struct RClass *mod)
 {
-  mod->mt = kh_init(mt, mrb);
+  if (!mod->mt) {
+    mod->mt = kh_init(mt, mrb);
+  }
 }

 static struct RClass*

@matz matz closed this in 38acb9e Jan 12, 2017

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