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GeezerVison is showing github.com — gh-89455: Fix an uninitialized bool in exception print context. by gpshead · Pull Request #91466 · python/cpython

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@gpshead

@gpshead gpshead commented Apr 12, 2022 •
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Fix an uninitialized bool in exception print context.

struct exception_print_context.need_close was uninitialized.

Found by oss-fuzz in a test case running under the undefined behavior sanitizer.

https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=46618
https://oss-fuzz.com/testcase-detail/6217746058182656

Python/pythonrun.c:1241:28: runtime error: load of value 253, which is not a valid value for type 'bool'
    #0 0xbf2203 in print_chained cpython3/Python/pythonrun.c:1241:28
    #1 0xbea4bb in print_exception_cause_and_context cpython3/Python/pythonrun.c:1320:19
    #2 0xbea4bb in print_exception_recursive cpython3/Python/pythonrun.c:1470:13
    #3 0xbe9e39 in _PyErr_Display cpython3/Python/pythonrun.c:1517:9

Pretty obvious what the ommission was upon code inspection.

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@ghost

ghost commented Apr 12, 2022

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@bedevere-bot bedevere-bot added the awaiting core review label Apr 12, 2022
@gpshead
gpshead requested a review from iritkatriel April 12, 2022 01:56
@gpshead

gpshead commented Apr 12, 2022

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Commit authors are required to sign the Contributor License Agreement.

The new CLA checker is broken and won't accept my current commits or even my attempt to re-sign the CLA via the bot here because of the way my arbitrary unverified text string git "email" field is structured in many of my local git config files. I'll keep this PR open as an example until that can be resolved.
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iritkatriel
iritkatriel approved these changes Apr 12, 2022
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This is initialised to false in line 1379, and the value is only used further down in the same function, so I don't think there's an actual bug (phew).

Yes, let's initialise it here too.

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@bedevere-bot bedevere-bot added awaiting merge and removed awaiting core review labels Apr 12, 2022
@gpshead gpshead self-assigned this Apr 13, 2022
gpshead added 2 commits April 13, 2022 00:46
@gpshead
Fix an uninitialized bool in exception print context.
40c65a3 
`struct exception_print_context.need_close` was uninitialized.

Found by oss-fuzz in a test case running under the undefined behavior sanitizer.

https://oss-fuzz.com/testcase-detail/6217746058182656

```
Python/pythonrun.c:1241:28: runtime error: load of value 253, which is not a valid value for type 'bool'
    #0 0xbf2203 in print_chained cpython3/Python/pythonrun.c:1241:28
    #1 0xbea4bb in print_exception_cause_and_context cpython3/Python/pythonrun.c:1320:19
    #2 0xbea4bb in print_exception_recursive cpython3/Python/pythonrun.c:1470:13
    #3 0xbe9e39 in _PyErr_Display cpython3/Python/pythonrun.c:1517:9
```

Pretty obvious what the ommission was upon code inspection.
@gpshead
Add a NEWS entry.
a012f40
@gpshead
gpshead force-pushed the bpo-45292-uninitialized_need_close branch from dc7f776 to a012f40 Compare April 13, 2022 00:47
@gpshead gpshead closed this Apr 13, 2022
@gpshead gpshead reopened this Apr 13, 2022
@gpshead gpshead added CLA signed and removed CLA signed labels Apr 13, 2022
@gpshead
update news wording.
6a19b93 
also see if a new commit re-triggers the CLA checker.
@gpshead
gpshead marked this pull request as ready for review April 14, 2022 18:22
@gpshead

gpshead commented Apr 14, 2022

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This is a real bug, the codepath in the traceback listed above used the value without it being initialized. Thus a sanitizer finding it. I don't think it had noticable behavioral impact though.
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@gpshead
gpshead merged commit 861974b into python:main Apr 14, 2022
@bedevere-bot bedevere-bot removed the awaiting merge label Apr 14, 2022
@gpshead
gpshead deleted the bpo-45292-uninitialized_need_close branch April 14, 2022 18:26
@illia-v illia-v mentioned this pull request Aug 5, 2023
Set up CIFuzz to run fuzz targets continuously #107652
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@gpshead @iritkatriel @bedevere-bot
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