gh-148735: Fix a UAF in Element.findtext()

[StanFromIreland]

This was a regression introduced by c57623c.

cpython/Modules/_elementtree.c

Line 575 in ae55e9c

/* return borrowed reference to text attribute */

• Issue: UAF in Element.findtext() when tag __eq__ mutates parent #148735

[picnixz]

All the occurrences you change are of the form (get borrowed) followed by (incref) right? if so, it is ok to change it to (get strong ref) but otherwise we may have un-necessary incref/decref. Currently XML is not FT-safe but if we (I) want to make it so, we should avoid incref/decref in hot paths

[serhiy-storchaka]

but otherwise we may have un-necessary incref/decref

The number of incerfs/decrefs remains the same. They are not unnecessary.

[picnixz]

Yeah I was not sure about this as I am on mobile. Thanks for checking

[serhiy-storchaka]

LGTM. 👍

[miss-islington-app]

Thanks @StanFromIreland for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14.
🐍🍒⛏🤖 I'm not a witch! I'm not a witch!

[miss-islington-app]

Sorry, @StanFromIreland, I could not cleanly backport this to 3.13 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 0469e6d38dcb3ff904690028cb3a25155bdcedae 3.13

[bedevere-app]

GH-148916 is a backport of this pull request to the 3.14 branch.

[StanFromIreland]

Thanks for the reviews!

[bedevere-app]

GH-148923 is a backport of this pull request to the 3.13 branch.