misc/142341: Jail escape when cwd is moved from the host system

[Vedad KAJTAZ]

>Number:         142341
>Category:       misc
>Synopsis:       Jail escape when cwd is moved from the host system
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Tue Jan 05 09:40:02 UTC 2010
>Closed-Date:
>Last-Modified:
>Originator:     Vedad KAJTAZ
>Release:        7.2-RELEASE-p4
>Organization:
Vedad KAJTAZ
>Environment:
FreeBSD kenny.osilex.net 7.2-RELEASE-p4 FreeBSD 7.2-RELEASE-p4 #0: Fri Oct  2 12:21:39 UTC 2009     root at i386-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC  i386
>Description:
Given the following setup:

- A host system
- A jail system located in /usr/local/jails/J1 on the host system 
- A shell open in the jail system, with cwd set to /some/path (therefore, /usr/local/jails/J1/some/path on the host system).

When the root moves the /usr/local/jails/J1/some/path folder somewhere else (say in /usr/local/jails/J2/some/path), the jail shell (as any other jail process) in no longer rooted and has access to the whole filesystem on the host.
Though this is not a common situation, it may happen (and did happen to me).

Best regards,
>How-To-Repeat:
Always repeatable
>Fix:
None known

>Release-Note:
>Audit-Trail:
>Unformatted: