mv:fix file ownership changes when a file is mv'ed by root to a different file system #9672
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… Unix Add functions to preserve file ownership (UID/GID) and permissions (mode) during mv operations when fs::rename fails and falls back to copy+remove. This ensures consistency with GNU mv behavior across filesystems, applying preservation in rename fallbacks for files, directories, symlinks, FIFOs, and recursive copies. Changes are Unix-specific, using libc::chown/lchown and fs::set_permissions.
Replace and_then with map in rename_file_fallback's copy operation for Unix systems, as the inner closure performs side effects and returns unit, making map more idiomatic than chaining with Ok(()). This improves code readability without altering behavior.
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GNU testsuite comparison: |
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Add a new Linux-only test to verify cross-device move behavior using user namespaces and tmpfs mounts, avoiding sudo. This mirrors GNU's part-fail scenario for directories containing dangling symlinks, ensuring the mv command preserves symlinks correctly in rootless environments.
- Modified HardlinkGroupScanner to skip symlinks using symlink_metadata, as hardlink preservation does not apply to them - Added copy_symlink functions for Unix, Windows, and other platforms to copy symlinks without dereferencing - Updated copy_dir_contents_recursive to detect and copy symlinks, including verbose output, preventing dereferencing during directory moves
Updated the copy_symlink function to use .map() combinator instead of .and_then() for clarity, as the closure performs a side effect (preserving ownership) and returns a unit value without chaining Results. This improves code readability and appropriateness of the combinator used.
Simplify the map closure by removing the explicit return of an empty tuple, as it is implicit in Rust when no value is needed. This improves code clarity without affecting functionality.
oech3
reviewed
Jan 1, 2026
| .env("BASE", &base) | ||
| .env("UUTILS", &scene.bin_path) | ||
| .output() | ||
| .expect("failed to run unshare"); |
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It might better to create a new function for uhshare (at different PR).
Ref: #9973
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Summary
Fix cross-filesystem
mv(EXDEV copy+delete fallback) so that file ownership does not change to the invoking user (e.g.root) when moving a file across filesystems.Fixes #9635.
Background / Problem
When
mvcannotrename(2)across devices (EXDEV), uutils falls back to copy+delete. The copy path usedstd::fs::copy, which creates the destination owned by the caller. Ifrootmoves a file owned by another user to a different filesystem, the destination ends up owned byroot(compatibility + security concern).Changes
lchown, do not follow)chownto keep correct permission bits (sincechownmay clear setuid/setgid)./dev/shmtmpfs).bind_instead_of_map) in the copy path.Testing
cargo test -p uu_mvcargo clippy -p uu_mv -- -D warningsrelated
#9635