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invalid assert on big output of multiprocessing.Process #78744

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ahcub mannequin opened this issue Sep 1, 2018 · 7 comments
Closed

invalid assert on big output of multiprocessing.Process #78744

ahcub mannequin opened this issue Sep 1, 2018 · 7 comments
Labels
3.7 (EOL) end of life 3.8 only security fixes stdlib Python modules in the Lib dir type-crash A hard crash of the interpreter, possibly with a core dump

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@ahcub
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ahcub mannequin commented Sep 1, 2018

BPO 34563
Nosy @pitrou, @vstinner, @applio, @ahcub
PRs
  • bpo-34563 Fix for invalid assert on big output of multiprocessing.Process #9025
  • bpo-34563 Fix for invalid assert on big output of multiprocessing.Process #9026
  • bpo-34563: Fix for invalid assert on big output of multiprocessing.Process #9027
  • [3.7] bpo-34563: Fix for invalid assert on big output of multiprocessing.Process (GH-9027) #9064
  • [3.6] bpo-34563: Fix for invalid assert on big output of multiprocessing.Process (GH-9027) #9069
    		•
    Files
  • invalid_assert_bug_reproduce.py
    		•

    Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.

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    GitHub fields:

    assignee = None
closed_at = <Date 2018-09-07.12:23:22.942>
created_at = <Date 2018-09-01.16:52:43.549>
labels = ['3.8', '3.7', 'library', 'type-crash']
title = 'invalid assert on big output of multiprocessing.Process'
updated_at = <Date 2018-09-07.15:37:51.831>
user = 'https://github.com/ahcub'

    bugs.python.org fields:

    activity = <Date 2018-09-07.15:37:51.831>
actor = 'ahcub'
assignee = 'none'
closed = True
closed_date = <Date 2018-09-07.12:23:22.942>
closer = 'vstinner'
components = ['Library (Lib)']
creation = <Date 2018-09-01.16:52:43.549>
creator = 'ahcub'
dependencies = []
files = ['47778']
hgrepos = []
issue_num = 34563
keywords = ['patch']
message_count = 7.0
messages = ['324465', '324497', '324594', '324601', '324735', '324736', '324764']
nosy_count = 4.0
nosy_names = ['pitrou', 'vstinner', 'davin', 'ahcub']
pr_nums = ['9025', '9026', '9027', '9064', '9069']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'crash'
url = 'https://bugs.python.org/issue34563'
versions = ['Python 3.6', 'Python 3.7', 'Python 3.8']
    @ahcub
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    ahcub mannequin commented Sep 1, 2018

    the bug is reproduced on big multiprocessing.Process output
    when the size of the output gets bigger than signed int the value becomes negative, thus

    assert left > 0

    in multiprocessing/connection.py:337 raises an exception like the following

    Traceback (most recent call last):
  File "D:\GitHub\cpython\lib\threading.py", line 917, in _bootstrap_inner
    self.run()
  File "D:\GitHub\cpython\lib\threading.py", line 865, in run
    self._target(*self._args, **self._kwargs)
  File "D:\GitHub\cpython\lib\multiprocessing\pool.py", line 470, in _handle_results
    task = get()
  File "D:\GitHub\cpython\lib\multiprocessing\connection.py", line 250, in recv
    buf = self._recv_bytes()
  File "D:\GitHub\cpython\lib\multiprocessing\connection.py", line 318, in _recv_bytes
    return self._get_more_data(ov, maxsize)
  File "D:\GitHub\cpython\lib\multiprocessing\connection.py", line 337, in _get_more_data
    assert left > 0
AssertionError

    this assert looks invalid in this case because in C code the left value is DWORD (unsigned long), which cannot be negative by definition.

    @ahcub ahcub mannequin added stdlib Python modules in the Lib dir type-crash A hard crash of the interpreter, possibly with a core dump 3.7 (EOL) end of life labels Sep 1, 2018
    @ahcub
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    ahcub mannequin commented Sep 3, 2018

    By bigger than signed int i meant bigger than positive signed int

    @vstinner
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    vstinner commented Sep 4, 2018

    New changeset 266f490 by Victor Stinner (Alexander Buchkovsky) in branch 'master':
    bpo-34563: Fix for invalid assert on big output of multiprocessing.Process (GH-9027)
    266f490

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    vstinner commented Sep 4, 2018

    New changeset e8ca880 by Victor Stinner (Miss Islington (bot)) in branch '3.7':
    bpo-34563: Fix for invalid assert on big output of multiprocessing.Process (GH-9027) (GH-9064)
    e8ca880

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    vstinner commented Sep 7, 2018

    New changeset 23f427a by Victor Stinner (Alexander Buchkovsky) in branch '3.6':
    [3.6] bpo-34563: Fix for invalid assert on big output of multiprocessing.Process (GH-9027) (GH-9069)
    23f427a

    @vstinner
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    vstinner commented Sep 7, 2018

    Thanks Alexander Buchkovsky for the fix: it has been merged into 3.6, 3.7 and master branches. Thanks Oleksandr Buchkovskyi for the bug report!

    --

    I looked at the Python 2.7 code and it doesn't look to be impacted by this bug.

    Modules/_multiprocessing/pipe_connection.c uses ReadFile() and PeekNamedPipe(), but the result type of the two C functions using it is not a PyObject* and conn_recv_string() looks good to me. Moreover, the type of the buflength parameter of conn_recv_string() is size_t, so there is no signed issue.

    @vstinner vstinner added the 3.8 only security fixes label Sep 7, 2018
    @vstinner vstinner closed this as completed Sep 7, 2018
    @ahcub
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    ahcub mannequin commented Sep 7, 2018

    thank you for all the help in merging this fix!

    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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