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Bad free in assemble function #87524

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alexhenrie mannequin opened this issue Mar 2, 2021 · 2 comments
Closed

Bad free in assemble function #87524

alexhenrie mannequin opened this issue Mar 2, 2021 · 2 comments
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3.10 interpreter-core type-crash

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@alexhenrie
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@alexhenrie alexhenrie mannequin commented Mar 2, 2021

BPO 43358
Nosy @markshannon, @alexhenrie
PRs
  • #24697
    		•

    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 = None
created_at = <Date 2021-03-02.01:38:32.270>
labels = ['interpreter-core', '3.10', 'type-crash']
title = 'Bad free in assemble function'
updated_at = <Date 2021-03-02.10:20:36.017>
user = 'https://github.com/alexhenrie'

    bugs.python.org fields:

    activity = <Date 2021-03-02.10:20:36.017>
actor = 'Mark.Shannon'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Interpreter Core']
creation = <Date 2021-03-02.01:38:32.270>
creator = 'alex.henrie'
dependencies = []
files = []
hgrepos = []
issue_num = 43358
keywords = ['patch']
message_count = 2.0
messages = ['387893', '387903']
nosy_count = 2.0
nosy_names = ['Mark.Shannon', 'alex.henrie']
pr_nums = ['24697']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'crash'
url = 'https://bugs.python.org/issue43358'
versions = ['Python 3.10']
    @alexhenrie
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    @alexhenrie alexhenrie mannequin commented Mar 2, 2021

    The assemble function in compile.c currently looks like this:

        static PyCodeObject *
    assemble(struct compiler *c, int addNone)
    {
        basicblock *b, *entryblock;
        struct assembler a;
        int j, nblocks;
        PyCodeObject *co = NULL;
        PyObject *consts = NULL;
        ...

            for (basicblock *b = c->u->u_blocks; b != NULL; b = b->b_list) {
            if (normalize_basic_block(b)) {
                goto error;
            }
        }

        if (ensure_exits_have_lineno(c)) {
            goto error;
        }
        ...

         error:
        Py_XDECREF(consts);
        assemble_free(&a);
        return co;
    }

    If normalize_basic_block or ensure_exits_have_lineno fails, the function will attempt to free a.a_bytecode, which has not yet been initialized, possibly leading to a program crash.

    The problematic code was added by commit 5977a79 to fix bpo-42246.

    Defect identified by scan-build <https://clang-analyzer.llvm.org/scan-build.html\>

    @alexhenrie alexhenrie mannequin added 3.10 interpreter-core type-crash labels Mar 2, 2021
    @markshannon
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    @markshannon markshannon commented Mar 2, 2021

    New changeset 503627f by Alex Henrie in branch 'master':
    bpo-43358: Fix bad free in assemble function (GH-24697)
    503627f

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