kern/175449: unionfs and devfs misbehaviour

[David Naylor]

>Number:         175449
>Category:       kern
>Synopsis:       unionfs and devfs misbehaviour
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sun Jan 20 14:50:00 UTC 2013
>Closed-Date:
>Last-Modified:
>Originator:     David Naylor
>Release:        
>Organization:
Private
>Environment:
FreeBSD ultra.dg 9.1-PRERELEASE FreeBSD 9.1-PRERELEASE #0: Wed Oct 10 21:08:01 SAST 2012     root at dragon.dg:/tmp/home/freebsd9/src/sys/MODULAR  amd64
>Description:
When creating a uniofs based chroot I discovered some strange behaviour with dev/.  
>How-To-Repeat:
# mkdir bottom-p bottom/dev top
# mount -t unionfs -o below bottom top
# mount -t tmpfs tmdevfs devfs top/dev
# ls -l top/dev/null
ls: top/dev/null: No such file or directory
# touch top/dev/null
# ls -l top/dev/null
-rw-r--r--  1 root  wheel  0 Jan 20 16:35 top/dev/null
# touch top/dev
# ls -l top/dev/null
crw-rw-rw-  1 root  wheel    0,  18 Jan 20 16:34 top/dev/null

>Fix:
Workaround:

# mkdir bottom-p bottom/dev top
# mount -t unionfs -o below bottom top
# mount -t tmpfs tmdevfs devfs top/dev
# touch top/dev

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