mnt: Fix fs_fully_visible to verify the root directory is visible

[ Upstream commit 7e96c1b0e0f495c5a7450dc4aa7c9a24ba4305bd ]

This fixes a dumb bug in fs_fully_visible that allows proc or sys to
be mounted if there is a bind mount of part of /proc/ or /sys/ visible.

Cc: stable@vger.kernel.org
Reported-by: Eric Windisch <ewindisch@docker.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
1 file changed