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[3.6] bpo-31852: Fix segfault caused by using the async soft keyword#4122

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vstinner merged 4 commits into
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pablogsal:bpo31852
Oct 31, 2017
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[3.6] bpo-31852: Fix segfault caused by using the async soft keyword#4122
vstinner merged 4 commits into
python:3.6from
pablogsal:bpo31852

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@pablogsal

@pablogsal pablogsal commented Oct 25, 2017 •
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This PR solves a segmentation fault in Python 3.6 caused by a combination of the async soft keyword and continuation lines. Steps to reproduce:

>>> async \
...
  File "<stdin>", line 1
    \ufffd\ufffdF\ufffd\ufffd
         ^
SyntaxError: invalid syntax
>>> async \
Segmentation fault

As @Haypo mentioned in the issue you can use this file to use the issue in the tokenizer to induce a buffer overflow. This PR solves this issue as well.

The current implementation checks if the current token is ASYNC and sets a sentient value (2) in the tok->async_def before looking for the token ahead (which is the step where the segfault happens). The value of tok->async_def gets overwritten after the lookahead by the usual value (1). As this particular issues are fixed by #1669 in the current master (3.7) this PR acts as a mere patch.

https://bugs.python.org/issue31852

@pablogsal

pablogsal commented Oct 26, 2017

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Should I add a NEWS entry?

@vstinner

vstinner commented Oct 26, 2017 via email

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@pablogsal

pablogsal commented Oct 27, 2017

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Added in e5b1993

@pablogsal

pablogsal commented Oct 30, 2017

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@Haypo There is anything more I should change?

@vstinner vstinner requested a review from 1st1 October 30, 2017 16:30
@vstinner

vstinner commented Oct 30, 2017

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@1st1: Would you mind to review this PR please?

1st1
1st1 approved these changes Oct 30, 2017
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I think this is an OK fix. Let's merge it.

@vstinner vstinner merged commit 690c36f into python:3.6 Oct 31, 2017
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vstinner commented Oct 31, 2017

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Thank you @pablogsal! I merged your PR.

@pablogsal pablogsal deleted the bpo31852 branch October 31, 2017 08:07
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