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

Aleksa Sarai
2020-01-02T03:59:41Z

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On 2020-01-01, Al Viro <viro@zeniv.linux.org.uk> wrote:
> On Thu, Jan 02, 2020 at 01:44:07AM +1100, Aleksa Sarai wrote:
>
> > 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 <cyphar@cyphar.com>
> > Tested-by: Aleksa Sarai <cyphar@cyphar.com>
>
> 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/>

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