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: |
Contributor
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Would you try to make the test rootless?: #8605 (comment) |
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.
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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