Fix --preserve-root

[Arcterus]

I'm fairly certain that if the --preserve-root in chgrp was wrong, it is wrong in other utilities as well.

[wimh]

chgrp will still follow a bind mount to root and continue:

mkdir /root/root
mount -o bind / /root/root
chgrp --preserve-root -R root /root -v

The same applies to a symbolic link (with -H).

ln -s / /root/root
./target/debug/deps/chgrp --preserve-root -R root /root -v -H

Though it will detect a file system loop if a symbolic link is pointing to a parent directory other than the root directory (ln -s /tmp /tmp/tmp).

[Arcterus]

I'm pretty sure the problem right now is because we are only checking if it's a bind mount to root or a symbolic link to root in traverse(), which is only called once. The WalkDir in dive_into() doesn't check for either of these cases, so it just keeps going unless you specifically give a bind mount to root or a symbolic link on the command-line.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[chrisdebian]

Hi, all. Has this been resolved?

[naoNao89]

resolved on main (fixed by PR #6042, later hardened with safe traversal), both symlink-to-/ with -HR and direct / with -R correctly warn and exit 1. I recommend closing #1004.

# build binary
cargo build -p uu_chgrp --release

# 1) Symlink to / with -H (follow symlink at top) and -R
tmpdir=$(mktemp -d); cd "$tmpdir"; ln -s / root_link
/path/to/repo/target/release/chgrp --preserve-root -HR wheel root_link; echo "(exit=$?)"

# 2) Direct / with -R
/path/to/repo/target/release/chgrp --preserve-root -R wheel /; echo "(exit=$?)"

Observed output:

it is dangerous to operate recursively on 'root_link' (same as '/')
use --no-preserve-root to override this failsafe

(exit=1)

it is dangerous to operate recursively on '/'
use --no-preserve-root to override this failsafe

(exit=1)

[Ecordonnier]

Closing because the issue is fixed according to latest comment.