userns:  Don't allow more user namespaces than pids.

To prevent denial of service attacks and general foolishness limit the
total number of user namespaces to the maximum number of pids we allow.

We may want to make the limit dynamic later but for now make the limit
the maximum number of pids our kernel can be configured to support.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
1 file changed