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Crash in _asyncio._swap_current_task due to improper reference counting #105987

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chgnrdv opened this issue Jun 22, 2023 · 0 comments · Fixed by #105989
Closed

Crash in _asyncio._swap_current_task due to improper reference counting #105987

chgnrdv opened this issue Jun 22, 2023 · 0 comments · Fixed by #105989
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topic-asyncio type-crash A hard crash of the interpreter, possibly with a core dump

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@chgnrdv
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chgnrdv commented Jun 22, 2023 •
edited by bedevere-bot

First appeared in a474e04, where given function was introduced.

Repro:

import _asyncio

class DummyLoop:
    pass

class DummyTask:
    pass

l = DummyLoop()
_asyncio._swap_current_task(l, DummyTask())
t = _asyncio._swap_current_task(l, None)

Output:

Modules/gcmodule.c:461: visit_decref: Assertion "!_PyObject_IsFreed(op)" failed
Enable tracemalloc to get the memory block allocation traceback

object address  : 0x7fedad081130
object refcount : 1
object type     : 0x55f665a81fe0
object type name: dict
object repr     : Segmentation fault (core dumped)

I'm working on a fix.

Linked PRs
@chgnrdv chgnrdv added the type-crash A hard crash of the interpreter, possibly with a core dump label Jun 22, 2023
chgnrdv added a commit to chgnrdv/cpython that referenced this issue Jun 22, 2023
@chgnrdv
pythongh-105987: Fix reference counting issue in '_asyncio._swap_curr…
586cd0d 
…ent_task'

'_PyDict_GetItem_KnownHash' returns borrowed reference to previous task object, so consequent calls to '_PyDict_DelItem_KnownHash'/'_PyDict_SetItem_KnownHash' can deallocate it before it will be returned from 'swap_current_task' function
@chgnrdv chgnrdv mentioned this issue Jun 22, 2023
Merged
kumaraditya303 pushed a commit that referenced this issue Jun 24, 2023
@chgnrdv
gh-105987: Fix reference counting issue in `_asyncio._swap_current_ta…
d2cbb6e 
…sk` (#105989)
@bedevere-bot bedevere-bot mentioned this issue Jun 26, 2023
Merged
kumaraditya303 pushed a commit to kumaraditya303/cpython that referenced this issue Jun 26, 2023
@chgnrdv @kumaraditya303
[3.12] pythongh-105987: Fix reference counting issue in `_asyncio._sw…
8f4c71c 
…ap_current_task` (pythonGH-105989).

(cherry picked from commit d2cbb6e)

Co-authored-by: chgnrdv <52372310+chgnrdv@users.noreply.github.com>
kumaraditya303 added a commit that referenced this issue Jun 26, 2023
@kumaraditya303 @chgnrdv
[3.12] gh-105987: Fix reference counting issue in `_asyncio._swap_cur… (
9e6f8d4 
#106099)

[3.12] gh-105987: Fix reference counting issue in `_asyncio._swap_current_task` (GH-105989).
(cherry picked from commit d2cbb6e)

Co-authored-by: chgnrdv <52372310+chgnrdv@users.noreply.github.com>
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Labels
topic-asyncio type-crash A hard crash of the interpreter, possibly with a core dump
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asyncio
Status: Done
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gh-105987: Fix reference counting issue in _asyncio._swap_current_task chgnrdv/cpython
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@chgnrdv @AlexWaygood