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Check index in PyTuple_GET_ITEM/PyTuple_SET_ITEM in debug mode #79518

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vstinner opened this issue Nov 28, 2018 · 12 comments
Closed

Check index in PyTuple_GET_ITEM/PyTuple_SET_ITEM in debug mode #79518

vstinner opened this issue Nov 28, 2018 · 12 comments
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3.8 only security fixes interpreter-core (Objects, Python, Grammar, and Parser dirs)

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@vstinner
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BPO 35337
Nosy @scoder, @vstinner, @skrah, @serhiy-storchaka, @ZackerySpytz
PRs
  • bpo-35337: Fix gettmarg(): use PyStructSequence_GET_ITEM() #10765
  • bpo-35337: PyTuple_GET_ITEM() now checks the index #10766
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    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 2018-12-17.11:22:21.208>
created_at = <Date 2018-11-28.13:17:08.129>
labels = ['interpreter-core', '3.8']
title = 'Check index in PyTuple_GET_ITEM/PyTuple_SET_ITEM in debug mode'
updated_at = <Date 2018-12-17.11:22:21.206>
user = 'https://github.com/vstinner'

    bugs.python.org fields:

    activity = <Date 2018-12-17.11:22:21.206>
actor = 'vstinner'
assignee = 'none'
closed = True
closed_date = <Date 2018-12-17.11:22:21.208>
closer = 'vstinner'
components = ['Interpreter Core']
creation = <Date 2018-11-28.13:17:08.129>
creator = 'vstinner'
dependencies = []
files = []
hgrepos = []
issue_num = 35337
keywords = ['patch']
message_count = 12.0
messages = ['330597', '330598', '330600', '330638', '330675', '330676', '331408', '331410', '331425', '331429', '331431', '331986']
nosy_count = 5.0
nosy_names = ['scoder', 'vstinner', 'skrah', 'serhiy.storchaka', 'ZackerySpytz']
pr_nums = ['10765', '10766']
priority = 'normal'
resolution = 'wont fix'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue35337'
versions = ['Python 3.8']
    @vstinner
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    I propose to add assertions to PyTuple_GET_ITEM/PyTuple_SET_ITEM in debug mode to check the index when Python is compiled in debug mode (./configure --with-pydebug).

    This change is backward incompatible when PyTuple_GET_ITEM/PyTuple_SET_ITEM is used on a structseq with unnamed fields. Well, that's a bug in the user code, PyStructSequence_GET_ITEM/PyStructSequence_SET_ITEM should be used instead.

    @vstinner vstinner added 3.8 only security fixes interpreter-core (Objects, Python, Grammar, and Parser dirs) labels Nov 28, 2018
    @vstinner
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    My commit df108dc already added assert(PyTuple_Check(op)) to these two macros.

    @vstinner
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    New changeset 1cdfcfc by Victor Stinner in branch 'master':
    bpo-35337: Fix gettmarg(): use PyStructSequence_GET_ITEM() (GH-10765)
    1cdfcfc

    @ZackerySpytz
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    ZackerySpytz mannequin commented Nov 28, 2018

    See also bpo-14614.

    @serhiy-storchaka
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    This is compatibility breaking change. Currently you can get the address of the array of tuple items by using &PyTuple_GET_ITEM(obj, 0).

    @vstinner
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    This is compatibility breaking change.

    Right. The question is if you are ok with it :-)

    Currently you can get the address of the array of tuple items by using &PyTuple_GET_ITEM(obj, 0).

    I don't get your point. I know that you access directly obj->ob_item to use directly the C array rather than PyTuple_GET_ITEM/PyTuple_SET_ITEM, but the issue is about making PyTuple_GET_ITEM/PyTuple_SET_ITEM stricter in debug mode.

    @serhiy-storchaka
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    I think we can break this only after adding public API for accessing internal storage of a tuple: PyTuple_ITEMS().

    And the same for lists.

    @scoder
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    scoder commented Dec 9, 2018

    If this is really just about debugging, then I would suggest to not break existing code at all.

    @skrah
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    skrah mannequin commented Dec 9, 2018

    I'm using &PyTuple_GET_ITEM(args, 0), so Serhiy's concern is not theoretical.

    I think if people want the safe version they should use PyTuple_GetItem().

    @skrah
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    skrah mannequin commented Dec 9, 2018

    Since this feature mainly helps when running a test suite using a debug build:

    The same can be achieved by running the test suite under Valgrind, which catches invalid accesses and a lot more.

    So I'd prefer to keep the macro in its current form.

    @skrah
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    skrah mannequin commented Dec 9, 2018

    If the feature is for the Python test suite itself, one solution would be to add -DPY_BOUNDS_CHECKS and use that on the buildbots.

    I still think making all of the test suite Valgrind-ready (most of it is, except test_multiprocessing and a few others) would catch more.

    @vstinner
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    Ok, I abandon my change.

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