fix: resolve symlinks in safe_path to prevent false rejections

[ChuxiJ]

The path safety module used os.path.normpath(os.path.abspath(...)) which does not resolve symlinks. On systems where the working directory is accessed through a symlink (e.g. /root/data -> /vepfs-d-data/q-ace), os.getcwd() returns the real path while user-entered paths retain the symlink prefix, causing startswith() to fail and legitimate dataset paths to be rejected as unsafe.

Switch to os.path.realpath() for all path normalisation so that both the safe root and user paths are resolved to their canonical form before comparison.

Summary by CodeRabbit

• Bug Fixes
  • Improved path validation to consistently resolve symbolic links during security checks, ensuring more reliable and predictable path access control.

[coderabbitai]

Caution

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📝 Walkthrough

Walkthrough

Introduces a private _resolve helper function to normalize and resolve symlinks in file paths. Updates safe_path validation and safe root initialization to consistently use realpath-based resolution for both root and user paths before prefix validation. Public interfaces remain unchanged.

Changes

Cohort / File(s)	Summary
Path Resolution Enhancement acestep/training/path_safety.py	Added _resolve helper for consistent symlink-aware path normalization. Updated safe root initialization and set_safe_root to use resolver. Modified safe_path to resolve relative user paths against root using realpath before validation. Error messages now reference resolved paths.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Poem

🐰 Symlinks and paths, now resolved with care,
The rabbit hops through each hidden lair,
No more confusion, no twisted trail,
With _resolve helper, safety won't fail! ✨

✨ Finishing Touches

• 📝 Generate docstrings (stacked PR)
• 📝 Generate docstrings (commit on current branch)

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix/safe-path-symlink-resolution

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