[ruby-core:113044] [Ruby master Bug#19554] Invalid memory access detected by Valgrind when using Fibers

Issue #19554 has been updated by ioquatix (Samuel Williams).


> I haven't looked too much into ASAN, I'll look into it further. My main concern with ASAN is the need for Ruby to be compiled with it turned on and that additional code may need to be added into native extensions to support it. Both of these are barriers to entry compared to Valgrind.


It's unlikely that Valgrind will work with CRuby out of the box without Valgrind specific code e.g. for marking stacks, poisoning dead code, etc. I am okay to help you try it. Just don't underestimate how complicated it can be to get all the right feedback. e.g. ASAN poison is used for GC to mark regions of the memory that should not be accessed. The same is true for fibers. It already all works.

----------------------------------------
Bug #19554: Invalid memory access detected by Valgrind when using Fibers
https://bugs.ruby-lang.org/issues/19554#change-102583

* Author: peterzhu2118 (Peter Zhu)
* Status: Open
* Priority: Normal
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN
----------------------------------------
This issue was originally reported here: https://github.com/Shopify/ruby_memcheck/issues/14

Running the script shown below using `valgrind --trace-children=yes --num-callers=500 ruby test.rb` outputs a lot of invalid memory access errors. I've shown a few sample errors below.

I am able to reproduce this issue on the master branch (commit [1e9a218ade](https://github.com/ruby/ruby/commit/1e9a218ade3af90c18f42e3fea08e2fcea81222a)), 3.2, 3.1, 3.0.


```ruby
require "bundler/inline"
gemfile do
  source "https://rubygems.org"
  gem "graphql"
end

module Example
  class FooType < GraphQL::Schema::Object
    field :id, ID, null: false
  end

  class FooSource < GraphQL::Dataloader::Source
    def fetch(ids)
      ids
    end
  end

  class QueryType < GraphQL::Schema::Object
    field :foo, Example::FooType do
      argument :foo_id, GraphQL::Types::ID, required: false, loads: Example::FooType
    end

    def foo(foo: nil); end
  end

  class Schema < GraphQL::Schema
    query Example::QueryType
    use GraphQL::Dataloader

    def self.object_from_id(id, ctx)
      ctx.dataloader.with(Example::FooSource).request(id)
    end
  end
end

Example::Schema.execute(<<-GRAPHQL)
{
  foo(fooId: "Other") {
    id
  }
}
GRAPHQL
```

```
==203957== Use of uninitialised value of size 8
==203957==    at 0x3453FD: vm_exec_core (vm.inc:4411)
==203957==    by 0x357EFB: rb_vm_exec (vm.c:2366)
==203957==    by 0x354E44: invoke_block (vm.c:1384)
==203957==    by 0x355759: invoke_iseq_block_from_c (vm.c:1440)
==203957==    by 0x355759: invoke_block_from_c_proc (vm.c:1538)
==203957==    by 0x355759: vm_invoke_proc (vm.c:1568)
==203957==    by 0x355DF4: rb_vm_invoke_proc (vm.c:1589)
==203957==    by 0x48F695: rb_fiber_start (cont.c:2513)
==203957==    by 0x48CCF8: fiber_entry (cont.c:831)
==203957==
==203957== Invalid write of size 8
==203957==    at 0x48C407: fiber_pool_stack_reset (cont.c:325)
==203957==    by 0x48C4E9: fiber_pool_vacancy_reset (cont.c:364)
==203957==    by 0x48CBB0: fiber_pool_stack_release (cont.c:752)
==203957==    by 0x48CECF: fiber_stack_release (cont.c:874)
==203957==    by 0x48FC9F: fiber_switch (cont.c:2726)
==203957==    by 0x4901F9: fiber_resume_kw (cont.c:2906)
==203957==    by 0x490235: rb_fiber_resume_kw (cont.c:2912)
==203957==    by 0x4903B7: rb_fiber_m_resume (cont.c:2973)
==203957==    by 0x3337D6: ractor_safe_call_cfunc_m1 (vm_insnhelper.c:3166)
==203957==    by 0x33440A: vm_call_cfunc_with_frame_ (vm_insnhelper.c:3357)
==203957==    by 0x3345E1: vm_call_cfunc_with_frame (vm_insnhelper.c:3385)
==203957==    by 0x3398E5: vm_sendish (vm_insnhelper.c:5225)
==203957==    by 0x341203: vm_exec_core (insns.def:835)
==203957==    by 0x357EFB: rb_vm_exec (vm.c:2366)
==203957==    by 0x354E44: invoke_block (vm.c:1384)
==203957==    by 0x355759: invoke_iseq_block_from_c (vm.c:1440)
==203957==    by 0x355759: invoke_block_from_c_proc (vm.c:1538)
==203957==    by 0x355759: vm_invoke_proc (vm.c:1568)
==203957==    by 0x355DF4: rb_vm_invoke_proc (vm.c:1589)
==203957==    by 0x48F695: rb_fiber_start (cont.c:2513)
==203957==    by 0x48CCF8: fiber_entry (cont.c:831)
==203957==  Address 0x9bad008 is in a rw- anonymous segment
```




-- 
https://bugs.ruby-lang.org/
 ______________________________________________
 ruby-core mailing list -- [e-mail]
 To unsubscribe send an email to [e-mail]
 ruby-core info -- https://ml.ruby-lang.org/mailman3/postorius/lists/ruby-core.ml.ruby-lang.org/