From: "toy (Ivan Kuchin) via ruby-core" <ruby-core@...>
Date: 2023-10-10T12:17:45+00:00
Subject: [ruby-core:114992] [Ruby master Bug#19917] Segmentation fault or lost objects when using Ractor.select with moved exceptions

Issue #19917 has been reported by toy (Ivan Kuchin).



----------------------------------------

Bug #19917: Segmentation fault or lost objects when using Ractor.select with moved exceptions

https://bugs.ruby-lang.org/issues/19917



* Author: toy (Ivan Kuchin)

* Status: Open

* Priority: Normal

* ruby -v: ruby 3.2.2 (2023-03-30 revision e51014f9c0) [x86_64-linux]

* Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN

----------------------------------------

I stumbled upon loss of messages with exceptions or even Segmentation fault during transfer of exception from Ractor when moving the exception. In versions 3.0 and 3.1 I saw only loss of messages, in 3.2 also Segmentation fault. Loss of messages happens only when using `Ractor.select` (not `Ractor#take`), but segmentation fault happens also using `Ractor#take`.



```ruby

100.times do

  ractor_count = 10



  ractors = Array.new(ractor_count) do |i|

    Ractor.new do

      begin

        raise 'foo'

      rescue => e

        # It is not possible to move exception without duplicating, but also

        # without it showing bactrace errors in 3.0 and is empty in 3.1+

        e = Marshal.load(Marshal.dump(e))

        Ractor.yield e, move: true

      end

      'message got lost'

    end

  end



  ractor_count.times do

    ractor, result = Ractor.select(*ractors)

    p result

    ractors.delete(ractor)

  end

end

```



In 3.0 and 3.1 will contain mix of `#<RuntimeError: foo>` and `"message got lost"`, in 3.2 may contain both and cause Segmentation fault. Excerpt of output (full output attached) from container running ruby:3.2 (`ruby 3.2.2 (2023-03-30 revision e51014f9c0) [x86_64-linux]`):

```

���

#<RuntimeError: RuntimeError>

"message got lost"

#<RuntimeError: RuntimeError>

#<RuntimeError: RuntimeError>

#<RuntimeError: RuntimeError>

#<RuntimeError: RuntimeError>

#<RuntimeError: RuntimeError>

#<RuntimeError: RuntimeError>

#<RuntimeError: RuntimeError>

#<RuntimeError: RuntimeError>

#<RuntimeError: RuntimeError>

#<RuntimeError: RuntimeError>

#<RuntimeError: RuntimeError>

#<RuntimeError: RuntimeError>

#<RuntimeError: RuntimeError>

#<RuntimeError: RuntimeError>

#<RuntimeError: RuntimeError>

#<RuntimeError: RuntimeError>

#<RuntimeError: RuntimeError>

#<RuntimeError: RuntimeError>

<internal:marshal>:34: [BUG] Segmentation fault at 0x0000000000000000

ruby 3.2.2 (2023-03-30 revision e51014f9c0) [x86_64-linux]



-- Control frame information -----------------------------------------------

c:0004 p:0006 s:0019 e:000018 METHOD <internal:marshal>:34

c:0003 p:0022 s:0011 e:000010 RESCUE (irb):11

c:0002 p:0007 s:0007 e:000006 BLOCK  (irb):6 [FINISH]

c:0001 p:---- s:0003 e:000002 DUMMY  [FINISH]



-- Ruby level backtrace information ----------------------------------------

(irb):6:in `block (3 levels) in <top (required)>'

(irb):11:in `rescue in block (3 levels) in <top (required)>'

<internal:marshal>:34:in `load'



-- Machine register context ------------------------------------------------

 RIP: 0x00007fabc1d64490 RBP: 0x0000000000000000 RSP: 0x00007fabbc71b0c0

 RAX: 0x0000000000000003 RBX: 0x00007fabbcebee88 RCX: 0x000000000000015f

 RDX: 0x0000556127db90f0 RDI: 0x000000000000015f RSI: 0x00007fabc2068628

  R8: 0x0000000000000001  R9: 0x0000000000000020 R10: 0x00005561285633d0

 R11: 0x0000000000000001 R12: 0x0000556127dbb710 R13: 0x00007fabc0601be0

 R14: 0x0000000000000018 R15: 0x0000000000000000 EFL: 0x0000000000010206

���

```



---Files--------------------------------

segmentation-fault.txt (27.8 KB)





-- 

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