Disallow the null character in type name

[serhiy-storchaka]

BPO	25961
Nosy	@serhiy-storchaka, @pppery, @florinpapa
Files	type_name_null.patch type_name_null_fix.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 2015-12-30.19:43:35.822>
created_at = <Date 2015-12-27.14:28:00.837>
labels = ['interpreter-core', 'type-bug']
title = 'Disallow the null character in type name'
updated_at = <Date 2015-12-31.10:08:15.852>
user = 'https://github.com/serhiy-storchaka'

bugs.python.org fields:

activity = <Date 2015-12-31.10:08:15.852>
actor = 'python-dev'
assignee = 'serhiy.storchaka'
closed = True
closed_date = <Date 2015-12-30.19:43:35.822>
closer = 'serhiy.storchaka'
components = ['Interpreter Core']
creation = <Date 2015-12-27.14:28:00.837>
creator = 'serhiy.storchaka'
dependencies = []
files = ['41434', '41460']
hgrepos = []
issue_num = 25961
keywords = ['patch']
message_count = 7.0
messages = ['257076', '257189', '257191', '257236', '257250', '257251', '257252']
nosy_count = 4.0
nosy_names = ['python-dev', 'serhiy.storchaka', 'ppperry', 'florin.papa']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue25961'
versions = ['Python 2.7', 'Python 3.5', 'Python 3.6']

[serhiy-storchaka]

The null character is allowed in __name__ setter (but error message is a little confusing).

>>> class A: pass
... 
>>> A.__name__ = 'B\0'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: __name__ must not contain null bytes

But is allowed in type constructor.

>>> t = type('B\0C', (), {})
>>> t
<class '__main__.BC'>
>>> t.__name__
'B\x00C'

[pppery]

Why are null bytes being excluded from type names in the first place?

[serhiy-storchaka]

Because tp_name is a pointer to null-terminated C string and there is no way to distinguish the name containg the null byte from the name terminated by null byte. tp_name is used for example in error messages.

>>> t = type('B\0C', (), {})
>>> t.__name__
'B\x00C'
>>> t() + 0
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for +: 'B' and 'int'

[python-dev]

New changeset 29cc6b2f9d28 by Serhiy Storchaka in branch '2.7':
Issue bpo-25961: Disallowed null characters in the type name.
https://hg.python.org/cpython/rev/29cc6b2f9d28

New changeset d2417971c934 by Serhiy Storchaka in branch '3.5':
Issue bpo-25961: Disallowed null characters in the type name.
https://hg.python.org/cpython/rev/d2417971c934

New changeset 1ab7bcd4e176 by Serhiy Storchaka in branch 'default':
Issue bpo-25961: Disallowed null characters in the type name.
https://hg.python.org/cpython/rev/1ab7bcd4e176

[florinpapa]

Hi all,

I fixed a compile error introduced in Python 2.7 by this issue. There is a jump made to an nonexistent label "error" in type_new function in Objects/typeobject.c. Please see the attached patch.

Regards,
Florin Papa

[serhiy-storchaka]

Thank you Florin. How could I miss this?

But your patch is not correct. It leads to double free and deallocating using non-initialized pointer. It also contains trailing spaces and incorrect indentation.

[python-dev]

New changeset 57fea6f75ac2 by Serhiy Storchaka in branch '2.7':
Issue bpo-25961: Fixed compilation error and a leak in type constructor.
https://hg.python.org/cpython/rev/57fea6f75ac2