umount: Disallow unprivileged mount force
authorEric W. Biederman <ebiederm@xmission.com>
Sat, 4 Oct 2014 21:44:03 +0000 (14:44 -0700)
committerEric W. Biederman <ebiederm@xmission.com>
Tue, 2 Dec 2014 16:46:48 +0000 (10:46 -0600)
commitb2f5d4dc38e034eecb7987e513255265ff9aa1cf
tree7a2205fdc3392feb549dfc55ce2c9f567b730936
parent4a44a19b470a886997d6647a77bb3e38dcbfa8c5
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>
fs/namespace.c