gh-149835: Resolve symlinks in shutil._destinsrc#149851
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Use os.path.realpath instead of os.path.abspath when normalising the src and dst paths in shutil._destinsrc. abspath only collapses '.' and '..' components, so a symlink anywhere in dst could let a destination that is physically inside src appear to be outside it in string space, silently bypassing the cross-device move guard in shutil.move and causing copytree to recurse infinitely. Add a regression test that constructs such a symlink and asserts _destinsrc still detects the containment.
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PR Author Agent⚡ on behalf of @ding-alex 👋 I'm driving this PR from here to merge. Here's what I'll do:
I'll post updates here as the PR progresses. Feel free to leave a comment anytime! Note: this PR was opened as a draft — @ding-alex, please mark it ready-for-review when you'd like reviewers requested. |
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PR Author Agent⚡ on behalf of @ding-alex @ding-alex PR is blocked by CLA signing. Please sign the Python Software Foundation CLA at https://cla.python.org/ — I can't resolve this from the agent. |
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Fixes #149835.
shutil.move, in the cross-device fallback path, uses_destinsrc(src, dst)to refuse moving a directory into itself (which would makecopytreerecurse infinitely). The guard normalises the two paths withos.path.abspathand then does a string-prefix check.abspathonly collapses./..components — it does not resolve symlinks — so a symlink component anywhere indstcan make a destination that is physically insidesrclook like it is outside in string space, and the guard silently passes.This change uses
os.path.realpathfor bothsrcanddstso the comparison is done on the resolved, canonical paths.A regression test (
TestMove.test_destinsrc_symlink_bypass) is added that constructs the symlink layout described in the issue and asserts that_destinsrccorrectly reports containment.Author: @ding-alex
Pull Request opened by Augment Code | View session
shutil.movecan move the dir into itself (with a symlink) #149835