gh-149449: Fix use-after-free in _PyUnicode_GetNameCAPI

[eendebakpt]

The cache stored the raw struct pointer extracted from unicodedata's _ucnhash_CAPI capsule without keeping a reference to the owning capsule. Dropping the module from sys.modules and running gc.collect() then freed the struct while \N{...} decoding and the namereplace codec handler were still using it. Hold a strong reference to the capsule on the interpreter state and Py_CLEAR it in _PyUnicode_Fini.

This needs backports I think, as it also affects python versions 3.10 to 3.15.

Claude was used to construct a PR.

• Issue: Deleting unicodedata from sys.modules can cause pointer use-after-free #149449

[kumaraditya303]

I think the simpler alternative to this is to just statically allocate _PyUnicode_Name_CAPI in unicodedata_create_capi.

[miss-islington-app]

Thanks @eendebakpt for the PR, and @kumaraditya303 for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14, 3.15.
🐍🍒⛏🤖

[bedevere-app]

GH-150352 is a backport of this pull request to the 3.15 branch.

[bedevere-app]

GH-150353 is a backport of this pull request to the 3.14 branch.

[bedevere-app]

GH-150354 is a backport of this pull request to the 3.13 branch.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot ARM64 macOS 3.x (tier-2) has failed when building commit 43c60ec.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/725/builds/13430) and take a look at the build logs.
4. Check if the failure is related to this commit (43c60ec) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/#/builders/725/builds/13430

Failed tests:

• test_ssl

Summary of the results of the build (if available):

==

Click to see traceback logs

remote: Enumerating objects: 16, done. remote: Counting objects: 9% (1/11) remote: Counting objects: 18% (2/11) remote: Counting objects: 27% (3/11) remote: Counting objects: 36% (4/11) remote: Counting objects: 45% (5/11) remote: Counting objects: 54% (6/11) remote: Counting objects: 63% (7/11) remote: Counting objects: 72% (8/11) remote: Counting objects: 81% (9/11) remote: Counting objects: 90% (10/11) remote: Counting objects: 100% (11/11) remote: Counting objects: 100% (11/11), done. remote: Compressing objects: 14% (1/7) remote: Compressing objects: 28% (2/7) remote: Compressing objects: 42% (3/7) remote: Compressing objects: 57% (4/7) remote: Compressing objects: 71% (5/7) remote: Compressing objects: 85% (6/7) remote: Compressing objects: 100% (7/7) remote: Compressing objects: 100% (7/7), done. remote: Total 16 (delta 4), reused 4 (delta 4), pack-reused 5 (from 1) 
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HEAD is now at 43c60ec2fdd gh-149449: Fix use-after-free in `_PyUnicode_GetNameCAPI` (#150323)
Switched to and reset branch 'main'
ranlib: warning: 'libpython3.16d.a(brc.o)' has no symbolsranlib: warning: 'libpython3.16d.a(dynamic_annotations.o)' has no symbolsranlib: warning: 'libpython3.16d.a(gc_free_threading.o)' has no symbolsranlib: warning: 'libpython3.16d.a(index_pool.o)' has no symbolsranlib: warning: 'libpython3.16d.a(jit.o)' has no symbolsranlib: warning: 'libpython3.16d.a(jit_publish.o)' has no symbolsranlib: warning: 'libpython3.16d.a(optimizer_analysis.o)' has no symbolsranlib: warning: 'libpython3.16d.a(optimizer_symbols.o)' has no symbolsranlib: warning: 'libpython3.16d.a(pymath.o)' has no symbolsranlib: warning: 'libpython3.16d.a(pystats.o)' has no symbolsranlib: warning: 'libpython3.16d.a(stackrefs.o)' has no symbolsranlib: warning: 'libpython3.16d.a(uniqueid.o)' has no symbolsmake: *** [buildbottest] Error 2