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GeezerVison is showing github.com — gh-159739: Hold the codec registry lock while unregistering by jelle-openai · Pull Request #160168 · python/cpython

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@jelle-openai

@jelle-openai jelle-openai commented Oct 22, 2026 •
edited by bedevere-app Bot
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Concurrent calls to codecs.unregister() can shrink the search path between its length check and indexed lookup in a free-threaded build. The lookup then returns NULL and an unconditional decref crashes the interpreter; hold the registry mutex across the scan and removal. Also reported in gh-157078. Backport to 3.15 and 3.14.

  • Issue: Fix minor safety issues #159739

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@jelle-openai
pythongh-159739: Hold the codec registry lock while unregistering
11a5f2d 
Concurrent calls to codecs.unregister() can shrink the search path between its length check and indexed lookup in a free-threaded build. The lookup then returns NULL and an unconditional decref crashes the interpreter; hold the registry mutex across the scan and removal. Also reported in pythongh-157078. Backport to 3.15 and 3.14.
@bedevere-app bedevere-app Bot mentioned this pull request Oct 22, 2026
Fix minor safety issues #159739
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@bedevere-app bedevere-app Bot added the awaiting review label Oct 22, 2026
@JelleZijlstra JelleZijlstra added needs backport to 3.14 bugs and security fixes needs backport to 3.15 bugs and security fixes labels Oct 22, 2026
@JelleZijlstra
JelleZijlstra enabled auto-merge (squash) October 22, 2026 18:23
@JelleZijlstra
JelleZijlstra merged commit 784b305 into python:main Oct 22, 2026
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@bedevere-app bedevere-app Bot removed the awaiting review label Oct 22, 2026
@miss-islington-app

miss-islington-app Bot commented Oct 22, 2026

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Thanks @jelle-openai for the PR, and @JelleZijlstra for merging it 🌮🎉.. I'm working now to backport this PR to: 3.14, 3.15.
🐍🍒⛏🤖
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@miss-islington-app

miss-islington-app Bot commented Oct 22, 2026

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Sorry, @jelle-openai and @JelleZijlstra, I could not cleanly backport this to 3.14 due to a conflict.

Please backport manually with cherry_picker, see the devguide for more information.

cherry_picker 784b305df8821d57fb6fb6c52794ef67bda0a75d 3.14
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@miss-islington-app miss-islington-app Bot assigned JelleZijlstra Oct 22, 2026
@bedevere-app

bedevere-app Bot commented Oct 22, 2026

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GH-160292 is a backport of this pull request to the 3.15 branch.
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@bedevere-app bedevere-app Bot removed the needs backport to 3.15 bugs and security fixes label Oct 22, 2026
JelleZijlstra pushed a commit that referenced this pull request Oct 22, 2026
@miss-islington @jelle-openai
[3.15] gh-159739: Hold the codec registry lock while unregistering (G…
47667b8 
…H-160168) (#160292)

Concurrent calls to codecs.unregister() can shrink the search path between its length check and indexed lookup in a free-threaded build. The lookup then returns NULL and an unconditional decref crashes the interpreter; hold the registry mutex across the scan and removal. Also reported in gh-157078. Backport to 3.15 and 3.14.
(cherry picked from commit 784b305)

Co-authored-by: Jelle Zijlstra <[email protected]>
@jelle-openai jelle-openai mentioned this pull request Oct 23, 2026
[3.14] gh-159739: Hold the codec registry lock while unregistering (GH-160168) #160485
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@bedevere-app

bedevere-app Bot commented Oct 23, 2026

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GH-160485 is a backport of this pull request to the 3.14 branch.
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@bedevere-app bedevere-app Bot removed the needs backport to 3.14 bugs and security fixes label Oct 23, 2026
JelleZijlstra pushed a commit that referenced this pull request Oct 24, 2026
@jelle-openai
[3.14] gh-159739: Hold the codec registry lock while unregistering (G…
72caed7 
…H-160168) (#160485)

Concurrent calls to codecs.unregister() can shrink the search path between its length check and indexed lookup in a free-threaded build. The lookup then returns NULL and an unconditional decref crashes the interpreter; hold the registry mutex across the scan and removal. Also reported in gh-157078. Backport to 3.15 and 3.14.
(cherry picked from commit 784b305)
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@jelle-openai @JelleZijlstra
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