Possible race condition in signal handling #102397

kumaraditya303 · 2023-03-03T13:33:40Z

The following code segfaults the interpreter on Linux. Tested on current main.

import gc
import _thread

gc.set_threshold(1, 0, 0)

def cb(*args):
    _thread.interrupt_main()


gc.callbacks.append(cb)

def gen():
    yield 1

g = gen()
g.__next__()

Exception ignored in: <function cb at 0x7f7f4f6fe200>
Traceback (most recent call last):
  File "/workspaces/cpython/main.py", line 7, in cb
    _thread.interrupt_main()
KeyboardInterrupt: 
Exception ignored in: <function cb at 0x7f7f4f6fe200>
Traceback (most recent call last):
  File "/workspaces/cpython/main.py", line 7, in cb
    _thread.interrupt_main()
KeyboardInterrupt: 
Exception ignored in: <function cb at 0x7f7f4f6fe200>
Traceback (most recent call last):
  File "/workspaces/cpython/main.py", line 7, in cb
    _thread.interrupt_main()
KeyboardInterrupt: 
Exception ignored in: <function cb at 0x7f7f4f6fe200>
Traceback (most recent call last):
  File "/workspaces/cpython/main.py", line 7, in cb
    _thread.interrupt_main()
KeyboardInterrupt: 
Segmentation fault (core dumped)

Linked PRs

GH-102397: Fix segfault from race condition in signal handling #102399

chgnrdv · 2023-03-03T14:04:29Z

Guess I found a minimal reproducer:

import _thread

class Foo():
    def __del__(self):
        _thread.interrupt_main()

x = Foo()

This, as well as original one, crashes on 3.10.8, 3.11.0 and current main under Linux.

kumaraditya303 · 2023-03-03T14:15:24Z

Yeah, both of these crashes are basically the same, they both crash in compare_handler in signal handling, I am working on a fix.

kumaraditya303 added type-bug An unexpected behavior, bug, or error interpreter-core (Objects, Python, Grammar, and Parser dirs) type-crash A hard crash of the interpreter, possibly with a core dump 3.12 labels Mar 3, 2023

bedevere-bot mentioned this issue Mar 3, 2023

GH-102397: Fix segfault from race condition in signal handling #102399

Open

Possible race condition in signal handling #102397

Possible race condition in signal handling #102397

kumaraditya303 commented Mar 3, 2023 •

edited by bedevere-bot

chgnrdv commented Mar 3, 2023

kumaraditya303 commented Mar 3, 2023

Possible race condition in signal handling #102397

Possible race condition in signal handling #102397

Comments

kumaraditya303 commented Mar 3, 2023 • edited by bedevere-bot

Linked PRs

chgnrdv commented Mar 3, 2023

kumaraditya303 commented Mar 3, 2023

kumaraditya303 commented Mar 3, 2023 •

edited by bedevere-bot