• Eric W. Biederman's avatar
    userns: Better restrictions on when proc and sysfs can be mounted · e51db735
    Eric W. Biederman authored
    Rely on the fact that another flavor of the filesystem is already
    mounted and do not rely on state in the user namespace.
    
    Verify that the mounted filesystem is not covered in any significant
    way.  I would love to verify that the previously mounted filesystem
    has no mounts on top but there are at least the directories
    /proc/sys/fs/binfmt_misc and /sys/fs/cgroup/ that exist explicitly
    for other filesystems to mount on top of.
    
    Refactor the test into a function named fs_fully_visible and call that
    function from the mount routines of proc and sysfs.  This makes this
    test local to the filesystems involved and the results current of when
    the mounts take place, removing a weird threading of the user
    namespace, the mount namespace and the filesystems themselves.
    Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
    e51db735
user.c 5.17 KB