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symtable_handle_namedexpr does not adjust correctly the recursion level #82128

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pablogsal opened this issue Aug 26, 2019 · 9 comments
Closed

symtable_handle_namedexpr does not adjust correctly the recursion level #82128

pablogsal opened this issue Aug 26, 2019 · 9 comments
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3.8 only security fixes 3.9 only security fixes 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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@pablogsal
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BPO 37947
Nosy @ncoghlan, @pablogsal, @miss-islington
PRs
  • bpo-37947: Adjust correctly the recursion level in symtable for named expressions #15499
  • [3.8] bpo-37947: Adjust correctly the recursion level in symtable for named expressions (GH-15499) #15515
  • bpo-37947: Avoid double-decrement in symtable recursion counting #15593
  • [3.8] bpo-37947: Avoid double-decrement in symtable recursion counting (GH-15593) #15594
    		•

    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 2019-08-26.15:28:36.283>
created_at = <Date 2019-08-26.03:09:10.895>
labels = ['interpreter-core', '3.8', '3.9', 'type-crash']
title = 'symtable_handle_namedexpr does not adjust correctly the recursion level'
updated_at = <Date 2019-09-03.07:49:39.607>
user = 'https://github.com/pablogsal'

    bugs.python.org fields:

    activity = <Date 2019-09-03.07:49:39.607>
actor = 'ncoghlan'
assignee = 'none'
closed = True
closed_date = <Date 2019-08-26.15:28:36.283>
closer = 'pablogsal'
components = ['Interpreter Core']
creation = <Date 2019-08-26.03:09:10.895>
creator = 'pablogsal'
dependencies = []
files = []
hgrepos = []
issue_num = 37947
keywords = ['patch']
message_count = 9.0
messages = ['350478', '350535', '350540', '350766', '350767', '350770', '350776', '350779', '351071']
nosy_count = 3.0
nosy_names = ['ncoghlan', 'pablogsal', 'miss-islington']
pr_nums = ['15499', '15515', '15593', '15594']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'crash'
url = 'https://bugs.python.org/issue37947'
versions = ['Python 3.8', 'Python 3.9']
    @pablogsal
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    The symtable_handle_namedexpr function does not adjust correctly the recursion level when exiting (also, is actually not returning anything in a function defined as non-void but the return value is not used so is not technically undefined behavior).

    @pablogsal pablogsal added 3.8 only security fixes 3.9 only security fixes interpreter-core (Objects, Python, Grammar, and Parser dirs) labels Aug 26, 2019
    @pablogsal
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    New changeset 0e4ea16 by Pablo Galindo in branch 'master':
    bpo-37947: Adjust correctly the recursion level in symtable for named expressions (GH-15499)
    0e4ea16

    @pablogsal
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    New changeset 3769425 by Pablo Galindo in branch '3.8':
    [3.8] bpo-37947: Adjust correctly the recursion level in symtable for named expressions (GH-15499) (GH-15515)
    3769425

    @ncoghlan
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    Reviewing the PR post-merge, I'm pretty sure this has introduced a double-decrement bug due to the original code being hard to read (the error cases did the decrement inside the helper function, while the success case did it in the calling function).

    #15593 builds on your PR by removing the recursion counter adjustments from inside the helper function, leaving only the ones in the calling function.

    @pablogsal
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    Thank you very much Nick for correcting this!

    @ncoghlan
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    Reviewing all the code that touches recursion_depth (both in the symtable and in the thread state), I'm not seeing any sanity checks that ensure our increments and decrements *balance*.

    So I'm going to add one to PySymTable_BuildObject.

    @ncoghlan
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    New changeset 0614523 by Nick Coghlan in branch 'master':
    bpo-37947: Avoid double-decrement in symtable recursion counting (GH-15593)
    0614523

    @miss-islington
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    New changeset 384c6d7 by Miss Islington (bot) in branch '3.8':
    bpo-37947: Avoid double-decrement in symtable recursion counting (GH-15593)
    384c6d7

    @ncoghlan
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    ncoghlan commented Sep 3, 2019

    We never actually coded a reproducer for this, but if we had, it would have been a crash bug.

    @ncoghlan ncoghlan added the type-crash A hard crash of the interpreter, possibly with a core dump label Sep 3, 2019
    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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    @ncoghlan @pablogsal @miss-islington