Prevent integer overflow in direct pipe write code from circumventing

Prevent integer overflow in direct pipe write code from circumventing
virtual-to-physical page lookups. [09:09]

Add missing permissions check for SIOCSIFINFO_IN6 ioctl. [09:10]

Fix buffer overflow in "autokey" negotiation in ntpd(8). [09:11]

Approved by:	so (cperciva)
Approved by:	re (not really, but SVN wants this...)
Security:	FreeBSD-SA-09:09.pipe
Security:	FreeBSD-SA-09:10.ipv6
Security:	FreeBSD-SA-09:11.ntpd

git-svn-id: svn://svn.freebsd.org/base/releng/7.2@193893 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f