misc/150972: symbolic link bug

[Bruce Evans]

On Sun, 26 Sep 2010, Kevin K. Han wrote:

>> Description:
> Create a directory on the root folder, for example ("/whatever").
> Switch to user's home directory ("cd /usr/home/username") ... from now onwards, work in this directory:
> Create a symbolic link from inside a user's home ("ln -s /whatever .")
> Execute this: ("chown -R username:username whatever")

Apparently you are still running as root after creating /whatever.  This
chown -R has no effect even as root.  (A plain chown would change /whatever
and chown -h would change the symlink.)

> Try to delete it using ("rm whatever")... it will say it is a directory. It is still not deleted!

I don't see this.  It would be a bad bug.  rm is required to not follow
symlinks.  A broken version of rm might stat() the symlink and decide
that it is a directory, and then rewrite its name to "whatever/" for
maximal brokenness (other utilities do need to append a slash sometimes,
and this is not easy to get right); then unlink("whatever/") would say
it is a directory.

> Then, try to delete using ("rm -r -f whatever/"), no errormessage, BUT It is still there!

This is how symlinks work.  "whatever/" is whatever the symlink points to.
It is "/whatever" here.  So this commands removes "/whatever" and leaves
the symlink untouched.

> Then, again, try the same thing ("rm whatever")... It is GONE, INCLUDING the original at "/whatever" !!!

Consistent with a broken rm stat()ing the symlink.  The previous command
removed "/whatever", so "whatever" is a dangling symlink and stat()ing it
wouldn't see it as a directory.

Bruce