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SharedMemory crash when size is 0 #85516

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vinay0410 mannequin opened this issue Jul 20, 2020 · 9 comments
Closed

SharedMemory crash when size is 0 #85516

vinay0410 mannequin opened this issue Jul 20, 2020 · 9 comments
Labels
3.8 only security fixes 3.10 only security fixes stdlib Python modules in the Lib dir type-bug An unexpected behavior, bug, or error

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@vinay0410
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vinay0410 mannequin commented Jul 20, 2020

BPO 41344
Nosy @terryjreedy, @pitrou, @applio, @pablogsal, @miss-islington, @vinay0410
PRs
  • bpo-41344: raise ValueError when creating shared memory of size 0 #21556
  • [3.9] bpo-41344: Raise ValueError when creating shared memory of size 0 (GH-21556) #22018
  • [3.8] bpo-41344: Raise ValueError when creating shared memory of size 0 (GH-21556) #22019
    		•

    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 2020-08-30.19:42:50.614>
created_at = <Date 2020-07-20.07:35:36.713>
labels = ['3.8', 'type-bug', 'library', '3.10']
title = 'SharedMemory crash when size is 0'
updated_at = <Date 2020-08-30.19:42:50.613>
user = 'https://github.com/vinay0410'

    bugs.python.org fields:

    activity = <Date 2020-08-30.19:42:50.613>
actor = 'pablogsal'
assignee = 'none'
closed = True
closed_date = <Date 2020-08-30.19:42:50.614>
closer = 'pablogsal'
components = ['Library (Lib)']
creation = <Date 2020-07-20.07:35:36.713>
creator = 'vinay0410'
dependencies = []
files = []
hgrepos = []
issue_num = 41344
keywords = ['patch']
message_count = 9.0
messages = ['373990', '374232', '374244', '374246', '374247', '376122', '376125', '376126', '376127']
nosy_count = 6.0
nosy_names = ['terry.reedy', 'pitrou', 'davin', 'pablogsal', 'miss-islington', 'vinay0410']
pr_nums = ['21556', '22018', '22019']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue41344'
versions = ['Python 3.8', 'Python 3.10']
    @vinay0410
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    vinay0410 mannequin commented Jul 20, 2020

    On running this: shm = SharedMemory(create=True, size=0)
    I get the following error:

    Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.8/multiprocessing/shared_memory.py", line 111, in __init__
    self._mmap = mmap.mmap(self._fd, size)
ValueError: cannot mmap an empty file
Error in sys.excepthook:
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/apport_python_hook.py", line 63, in apport_excepthook
    from apport.fileutils import likely_packaged, get_recent_crashes
  File "/usr/lib/python3/dist-packages/apport/__init__.py", line 5, in <module>
    from apport.report import Report
  File "/usr/lib/python3/dist-packages/apport/report.py", line 30, in <module>
    import apport.fileutils
  File "/usr/lib/python3/dist-packages/apport/fileutils.py", line 23, in <module>
    from apport.packaging_impl import impl as packaging
  File "/usr/lib/python3/dist-packages/apport/packaging_impl.py", line 24, in <module>
    import apt
  File "/usr/lib/python3/dist-packages/apt/__init__.py", line 23, in <module>
    import apt_pkg
ModuleNotFoundError: No module named 'apt_pkg'
    Original exception was:
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.8/multiprocessing/shared_memory.py", line 111, in __init__
    self._mmap = mmap.mmap(self._fd, size)
ValueError: cannot mmap an empty file
>>> shm = SharedMemory(create=True, size=0)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.8/multiprocessing/shared_memory.py", line 111, in __init__
    self._mmap = mmap.mmap(self._fd, size)
ValueError: cannot mmap an empty file
Error in sys.excepthook:
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/apport_python_hook.py", line 63, in apport_excepthook
    from apport.fileutils import likely_packaged, get_recent_crashes
  File "/usr/lib/python3/dist-packages/apport/__init__.py", line 5, in <module>
    from apport.report import Report
  File "/usr/lib/python3/dist-packages/apport/report.py", line 30, in <module>
    import apport.fileutils
  File "/usr/lib/python3/dist-packages/apport/fileutils.py", line 23, in <module>
    from apport.packaging_impl import impl as packaging
  File "/usr/lib/python3/dist-packages/apport/packaging_impl.py", line 24, in <module>
    import apt
  File "/usr/lib/python3/dist-packages/apt/__init__.py", line 23, in <module>
    import apt_pkg
ModuleNotFoundError: No module named 'apt_pkg'

Original exception was:
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.8/multiprocessing/shared_memory.py", line 111, in __init__
    self._mmap = mmap.mmap(self._fd, size)
ValueError: cannot mmap an empty file

    This can be simply resolved by adding a check when size passed is 0, so that a shared memory segment is never created.
    Currently, the following is coded:

    if not size >= 0:
    raise ValueError("'size' must be a positive integer")

    I believe this should be changed to:
    if not size > 0:
    raise ValueError("'size' must be a positive integer")

    As zero is not a positive and integer and is causing problems.

    @vinay0410 vinay0410 mannequin added type-crash A hard crash of the interpreter, possibly with a core dump 3.8 only security fixes stdlib Python modules in the Lib dir labels Jul 20, 2020
    @SilentGhost SilentGhost mannequin added type-bug An unexpected behavior, bug, or error and removed type-crash A hard crash of the interpreter, possibly with a core dump labels Jul 20, 2020
    @terryjreedy
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    Python 3.10.0a0 Jul 23 2020, win32 (without patch)

    >>> from multiprocessing import shared_memory
>>> shm_a = shared_memory.SharedMemory(create=True, size=0)
Traceback (most recent call last):
  File "<pyshell#1>", line 1, in <module>
    shm_a = shared_memory.SharedMemory(create=True, size=0)
  File "f:\dev\3x\lib\multiprocessing\shared_memory.py", line 129, in __init__
    h_map = _winapi.CreateFileMapping(
OSError: [WinError 87] The parameter is incorrect: 'wnsm_4ab39616'

    After the patch, I get the value error.

    @terryjreedy terryjreedy added 3.10 only security fixes labels Jul 25, 2020
    @vinay0410
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    vinay0410 mannequin commented Jul 25, 2020

    Hi, The patch aims to raise a value error, because before the patch also, ValueError was being raised in case size was negative. That's why I thought it would be correct behaviour if I raise ValueError in case size is 0.

    Do you mean to say, that OSError should be raise in the case size=0.
    Also, I think handling of Windows was fine even before the patch, it was MacOS and Linux which were causing problems.

    @vinay0410
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    vinay0410 mannequin commented Jul 25, 2020

    Also, Linux created the shared memory with the passed name if size = 0, but threw error when it was being mapped to the process's virtual memory. Therefore, this scenario should be prevented before actually creating the shared memory segment in cases of Linux.

    @terryjreedy
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    No, I think ValueError on all systems is better. I have no idea what 'wnsm_4ab39616' is about other than something internal to Windows. It does not say what to do to correct the call.

    @pablogsal
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    New changeset 475a5fb by Vinay Sharma in branch 'master':
    bpo-41344: Raise ValueError when creating shared memory of size 0 (GH-21556)
    475a5fb

    @pablogsal
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    New changeset ca55ecb by Miss Islington (bot) in branch '3.9':
    bpo-41344: Raise ValueError when creating shared memory of size 0 (GH-21556) (GH-22018)
    ca55ecb

    @pablogsal
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    New changeset 38e3287 by Miss Islington (bot) in branch '3.8':
    bpo-41344: Raise ValueError when creating shared memory of size 0 (GH-21556) (GH-22019)
    38e3287

    @pablogsal
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    Thanks for the report and the PR, vinay0410!

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