jailutils security issue, and possible issue with 'jail'

[Nielsen]

Since some of you use the jailutils package, I just wanted to post some 
additional info on the recent 'security fix' and also highlight a 
possible issue with the 'jail' command.

http://memberwebs.com/nielsen/freebsd/jails/jailutils/security.html

It's not a very big issue (unless I'm missing something), simply one of 
leaking the host environment into the jail.

This might be used legitimately in certain cases, but in most cases it's 
probably a good idea to clear out the environment before executing the 
jail() or jail_attach() syscalls.

The 'jstart' utility included in jailutils does this and it would 
probably be a good addition to 'jexec' and/or 'jail'.