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Incorrect use of PyObject_IsInstance #68445

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serhiy-storchaka opened this issue May 21, 2015 · 6 comments
Closed

Incorrect use of PyObject_IsInstance #68445

serhiy-storchaka opened this issue May 21, 2015 · 6 comments
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@serhiy-storchaka
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extension-modules C modules in the Modules dir interpreter-core (Objects, Python, Grammar, and Parser dirs) type-crash A hard crash of the interpreter, possibly with a core dump

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@serhiy-storchaka
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BPO 24257
Nosy @rhettinger, @bitdancer, @serhiy-storchaka
Files
  • typecheck.patch
  • typecheck_2.patch
    		•

    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 = 'https://github.com/serhiy-storchaka'
closed_at = <Date 2015-05-22.08:24:25.805>
created_at = <Date 2015-05-21.08:40:46.663>
labels = ['extension-modules', 'interpreter-core', 'type-crash']
title = 'Incorrect use of PyObject_IsInstance'
updated_at = <Date 2015-05-22.08:24:25.804>
user = 'https://github.com/serhiy-storchaka'

    bugs.python.org fields:

    activity = <Date 2015-05-22.08:24:25.804>
actor = 'serhiy.storchaka'
assignee = 'serhiy.storchaka'
closed = True
closed_date = <Date 2015-05-22.08:24:25.805>
closer = 'serhiy.storchaka'
components = ['Extension Modules', 'Interpreter Core']
creation = <Date 2015-05-21.08:40:46.663>
creator = 'serhiy.storchaka'
dependencies = []
files = ['39450', '39453']
hgrepos = []
issue_num = 24257
keywords = ['patch']
message_count = 6.0
messages = ['243739', '243752', '243754', '243756', '243797', '243820']
nosy_count = 4.0
nosy_names = ['rhettinger', 'r.david.murray', 'python-dev', 'serhiy.storchaka']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'crash'
url = 'https://bugs.python.org/issue24257'
versions = ['Python 2.7', 'Python 3.4', 'Python 3.5']
    @serhiy-storchaka
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    PyObject_IsInstance() is used incorrectly for testing if Python object is an instance of specified builtin type before direct access to internals of object. This is not correct, because PyObject_IsInstance() checks the __class__ attribute that can be modified and even can be dynamic property. Correct way is to check static type. Proposed patch replaces PyObject_IsInstance() with PyObject_TypeCheck() if this is appropriate.

    See also similar issues bpo-24102 and bpo-24091.

    @serhiy-storchaka serhiy-storchaka added extension-modules C modules in the Modules dir interpreter-core (Objects, Python, Grammar, and Parser dirs) type-crash A hard crash of the interpreter, possibly with a core dump labels May 21, 2015
    @bitdancer
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    Is there any chance that these changes will break working code, or is it the case that if the current check passes incorrectly one will always get a segfauilt or other error?

    @rhettinger
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    is it the case that if the current check passes incorrectly
    one will always get a segfauilt or other error?

    Yes, that is the case. All four of these checks precede a reference to an structure member that depends on being an exact type or subtype. So, yes they are all necessary to prevent segfaults or other undefined behavior.

    @serhiy-storchaka
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    Yes, it is the case that if the current check passes incorrectly one will always get a segfauilt or other error.

    Added tests for types.SimpleNamespace and sqlite3.Cursor. It is not easy to reproduce a bug for StopIterator (not sure it is reproducible), but the code looks definitely erroneous in any case.

    @rhettinger
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    Serhiy, go ahead and apply your patch. The existing code is clearly wrong.

    @python-dev
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    python-dev mannequin commented May 22, 2015

    New changeset bccaba8a5482 by Serhiy Storchaka in branch '2.7':
    Issue bpo-24257: Fixed segmentation fault in sqlite3.Row constructor with faked
    https://hg.python.org/cpython/rev/bccaba8a5482

    New changeset c7b9645a6f35 by Serhiy Storchaka in branch '3.4':
    Issue bpo-24257: Fixed incorrect uses of PyObject_IsInstance().
    https://hg.python.org/cpython/rev/c7b9645a6f35

    New changeset a5101529a8a9 by Serhiy Storchaka in branch 'default':
    Issue bpo-24257: Fixed incorrect uses of PyObject_IsInstance().
    https://hg.python.org/cpython/rev/a5101529a8a9

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

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