Re: [PATCH RFC 0/1] mount: universally disallow mounting over symlinks

On 2020-01-01, Al Viro [off-list ref] wrote:

On Thu, Jan 02, 2020 at 01:44:07AM +1100, Aleksa Sarai wrote:

quoted

Thanks, this fixes the issue for me (and also fixes another reproducer I
found -- mounting a symlink on top of itself then trying to umount it).

Reported-by: Aleksa Sarai <redacted>
Tested-by: Aleksa Sarai <redacted>

Pushed into #fixes.

Thanks. One other thing I noticed is that umount applies to the
underlying symlink rather than the mountpoint on top. So, for example
(using the same scripts I posted in the thread):

  # ln -s /tmp/foo link
  # ./mount_to_symlink /etc/passwd link
  # umount -l link # will attempt to unmount "/tmp/foo"

Is that intentional?

-- 
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
<https://www.cyphar.com/>