OSError: Bad file descriptor in madbg/debugger.py, sometimes, when connecting to running process

[DavidAntliff]

Not sure if this is expected or a known issue. Please take the following program, loop.py:

import time

i = 0
while True:
    i = i + 1
    print(i)
    time.sleep(0.001)

Run it: python loop.py and it will start outputting sequential numbers.

In another shell, run madbg (1.3.2):

$ madbg attach $(pgrep -f loop.py)

The shell running loop.py will typically stop with something like:

Waiting for debugger client on 127.0.0.1:3513
Debugger client connected from ('127.0.0.1', 46754)

And the madbg shell will show an ipdb> prompt - so far so good. Hit 'Q' + Enter to quit ipdb and the loop.py count will continue.

Repeat running madbg attach a few times, eventually the following will occur as loop.py terminates:

5380
5381
5382
Traceback (most recent call last):
  File loop.py, line 5, in <module>
    while True:
  File loop.py, line 5, in <module>
    while True:
  File venv/lib/python3.10/site-packages/madbg/debugger.py, line 64, in trace_dispatch
    return super().trace_dispatch(frame, event, arg)
  File /usr/lib/python3.10/bdb.py, line 90, in trace_dispatch
    return self.dispatch_line(frame)
  File /usr/lib/python3.10/bdb.py, line 114, in dispatch_line
    self.user_line(frame)
  File /usr/lib/python3.10/pdb.py, line 262, in user_line
    self.interaction(frame, None)
  File venv/lib/python3.10/site-packages/IPython/core/debugger.py, line 337, in interaction
    OldPdb.interaction(self, frame, traceback)
  File /usr/lib/python3.10/pdb.py, line 356, in interaction
    self.print_stack_entry(self.stack[self.curindex])
  File venv/lib/python3.10/site-packages/IPython/core/debugger.py, line 411, in print_stack_entry
    print(self.format_stack_entry(frame_lineno, '', context), file=self.stdout)
OSError: [Errno 9] Bad file descriptor
Exception ignored in: <module 'threading' from '/usr/lib/python3.10/threading.py'>
Traceback (most recent call last):
  File /usr/lib/python3.10/threading.py, line 1537, in _shutdown
    atexit_call()
  File /usr/lib/python3.10/contextlib.py, line 584, in close
    self.__exit__(None, None, None)
  File /usr/lib/python3.10/contextlib.py, line 576, in __exit__
    raise exc_details[1]
  File /usr/lib/python3.10/contextlib.py, line 561, in __exit__
    if cb(*exc_details):
  File /usr/lib/python3.10/contextlib.py, line 142, in __exit__
    next(self.gen)
  File venv/lib/python3.10/site-packages/madbg/debugger.py, line 170, in start_from_new_connection
    with cls.start(sock.fileno()) as debugger:
  File /usr/lib/python3.10/contextlib.py, line 142, in __exit__
    next(self.gen)
  File venv/lib/python3.10/site-packages/madbg/debugger.py, line 147, in start
    print('Closing connection', file=slave_writer, flush=True)
OSError: [Errno 9] Bad file descriptor

The madbg instance will have simply terminated with no output, error code 0.

My environment:

$ python --version
3.10.6

$ pip list  | grep hypno
hypno                  1.0.3

$ pip list | grep pyinjector
pyinjector             1.3.0

$ pip list | grep ipython
ipython                8.3.0

$ lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 22.04.2 LTS
Release:	22.04
Codename:	jammy

[kmaork]

Thank you for all the details! I'm working on a new version for madbg, in which a lot of the code is changed. I think I'll wait to see if it happens in the new version as well.