[Question] Unlinking original file of bind mounted file.

[Yun Levi <ppbuk5246@gmail.com>]

Hello fs-devel folks,

I have a few questions about below situation's handling.

======================================================
1. mount --bind {somefile} {target}
2. rm -f {somefile}
=======================================================

when it happens, the step (2)'s operation is working -- it removes.
But, the inode of {somefile} is live with i_nlink = 0 with an orphan
state of ext4_inode_info in ext4-fs.

IIUC, because ext4-inode-entry is removed in the disk via ext4_unlink,
and it seems possible
the inode_entry which is freed by unlink in step(2) will be used again
when a new file is created.

Suggest new created file which recycled the inode_entry unlinked by step(2).
and bind mounted-file is live.
In that situation, it seems that  via bind mount-file, it can
manipulate the data of the newly created file and access it
arbitrarily.

I don't know if it's right  to allow access to the removed file via
binded-file and it's the spec of filesystems or designed action by
ext4 filesystem only.

Thanks.

-- 
Best regards,
Levi