fs.cp and fs.cpSync fail to repeatedly copy directory with symlinks

Version

v24.16.0

Platform

Linux machine 7.1.3-cachyos-lto #1-NixOS SMP PREEMPT_DYNAMIC Tue Jan  1 00:00:00 UTC 1980 x86_64 GNU/Linux

Subsystem

fs

What steps will reproduce the bug?

This script reproduces the issue:

root="$(mktemp -d)"
trap 'rm -rf "$root"' EXIT

mkdir "$root/dir" "$root/foo"
ln -s "$root/dir" "$root/foo/link"

ROOT="$root" node <<'NODE'
const fs = require("node:fs");
const root = process.env.ROOT;

fs.cpSync(`${root}/foo`, `${root}/bar`, { recursive: true }); // succeeds
fs.cpSync(`${root}/foo`, `${root}/bar`, { recursive: true }); // throws
NODE

How often does it reproduce? Is there a required condition?

Requires a copying repeatedly a dir containing a symlink to another dir.

What is the expected behavior? Why is that the expected behavior?

The second copy should succeed, replacing bar/link or leaving it unchanged.

What do you see instead?

node:internal/fs/cp/cp-sync:145
    return fsBinding.cpSyncCopyDir(src, dest,
                     ^

Error: Cannot copy /tmp/tmp.61ap1tNPej/dir to a subdirectory of self /tmp/tmp.61ap1tNPej/dir
    at copyDir (node:internal/fs/cp/cp-sync:145:22)
    at onDir (node:internal/fs/cp/cp-sync:137:10)
    at getStats (node:internal/fs/cp/cp-sync:68:12)
    at cpSyncFn (node:internal/fs/cp/cp-sync:58:10)
    at Object.cpSync (node:fs:3158:3)
    at [stdin]:5:4
    at runScriptInThisContext (node:internal/vm:219:10)
    at node:internal/process/execution:451:12
    at [stdin]-wrapper:6:24
    at runScriptInContext (node:internal/process/execution:449:60) {
  code: 'ERR_FS_CP_EINVAL'
}

Node.js v24.16.0

Additional information

Also recreated in:

• Node.js v22.23.1
• Node.js v26.7.0
• Node.js v27.0.0-nightly20260806de333e856d

The result is the same with force: true, force: false, or errorOnExist. fs.cp() and fs.promises.cp() are also affected.

Modifying bar/link, or pointing it to a different directory, makes the second copy succeed.

Bắt đầu bằng việc tái hiện với node:fs và theo dõi các mục trong stack tại node:internal/fs/cp/cp-sync, đặc biệt là copyDir, onDir và getStats. Kiểm tra trường hợp sao chép đệ quy lặp lại với một symbolic link đến thư mục, sau đó xác minh rằng fs.cpSync, fs.cp và fs.promises.cp hoàn tất thành công lần sao chép thứ hai mà không thay đổi hành vi đã được báo cáo đối với thư mục con của chính nó.