Fix kernel memory disclosure in control message and SCTP notifications.

Security:	FreeBSD-SA-14:17.kmem
Security:	CVE-2014-3952, CVE-2014-3953
Approved by:	so


git-svn-id: svn+ssh://svn.freebsd.org/base/releng/9.2@268434 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f