tree 7a2205fdc3392feb549dfc55ce2c9f567b730936
parent 4a44a19b470a886997d6647a77bb3e38dcbfa8c5
author Eric W. Biederman <ebiederm@xmission.com> 1412459043 -0700
committer Eric W. Biederman <ebiederm@xmission.com> 1417538808 -0600

umount: Disallow unprivileged mount force

Forced unmount affects not just the mount namespace but the underlying
superblock as well.  Restrict forced unmount to the global root user
for now.  Otherwise it becomes possible a user in a less privileged
mount namespace to force the shutdown of a superblock of a filesystem
in a more privileged mount namespace, allowing a DOS attack on root.

Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>