New submission from STINNER Victor <vstin...@redhat.com>:
Attached dagpool_test.py script triggers a crash on Python 3.7, but works well
on Python 3.6. The script is a highly simplified code of tests/dagpool_tests.py
of eventlet.
To reproduce the crash, you only need a single dependency: greenlet. Example
using a venv:
python3.7 -m venv ENV
ENV/bin/python -m pip install greenlet
Then run the script:
$ test_venv/bin/python dagpool_test.py
Segmentation fault (core dumped)
eventlet bug report:
https://github.com/eventlet/eventlet/issues/475
I suspected that the bug is caused by the new exc_info attribute of
PyThreadState: commit ae3087c6382011c47db82fea4d05f8bbf514265d.
$ gdb -args test_venv/bin/python -X faulthandler dagpool_test.py
(gdb) run
Program received signal SIGSEGV, Segmentation fault.
0x000000000056c9d2 in PyErr_SetObject (exception=<type at remote 0x9709a0>,
value=0x0) at Python/errors.c:101
101 Py_INCREF(exc_value);
(gdb) where
#0 0x000000000056c9d2 in PyErr_SetObject (exception=<type at remote 0x9709a0>,
value=0x0) at Python/errors.c:101
#1 0x000000000056cd4e in PyErr_SetNone (exception=<type at remote 0x9709a0>)
at Python/errors.c:162
#2 0x000000000067cb0c in gen_send_ex (gen=0x7fffea651d78, arg=0x0, exc=0,
closing=0) at Objects/genobject.c:241
#3 0x000000000067dd86 in gen_iternext (gen=0x7fffea651d78) at
Objects/genobject.c:542
#4 0x00000000005461b1 in _PyEval_EvalFrameDefault (...)
...
(gdb) p tstate
$1 = (PyThreadState *) 0xa132a0
(gdb) p tstate->exc_info
$2 = (_PyErr_StackItem *) 0x7fffea651930
(gdb) p *tstate->exc_info
$3 = {
exc_type = 0x0,
exc_value = 0x0,
exc_traceback = 0x0,
previous_item = 0x7fffea651d20
}
(gdb) p *tstate->exc_info->previous_item
$4 = {
exc_type = <unknown at remote 0xdbdbdbdbdbdbdbdb>,
exc_value = <unknown at remote 0xdbdbdbdbdbdbdbdb>,
exc_traceback = <unknown at remote 0xdbdbdbdbdbdbdbdb>,
previous_item = 0xdbdbdbdbdbdbdbdb
}
----------
components: Interpreter Core
files: dagpool_test.py
keywords: 3.7regression
messages: 320712
nosy: Mark.Shannon, ned.deily, vstinner, yselivanov
priority: release blocker
severity: normal
status: open
title: Crash in gen_send_ex(): _PyErr_GetTopmostException() returns freed memory
versions: Python 3.7, Python 3.8
Added file: https://bugs.python.org/file47658/dagpool_test.py
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<https://bugs.python.org/issue33996>
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