re: kern/45700: /chroot/proc/mounts exposes out-of-chroot pathnames

[matthew green <mrg%eterna.com.au@localhost>]

> Machine: i386
> >Description:
> 
>       If I'm chrooted in /chroot, and I mount procfs on /proc (in the
>       chroot), then /proc/mounts exposes pathnames from outside the
>       chroot.
> 
> >How-To-Repeat:
> 
>       # chroot /chroot
>       # mount -t procfs procfs /proc
>       # cat /proc/mounts
> 
> >Fix:
> 
>       Yes, please!  It's not clear what the right behaviour is, but
>       perhaps a hack similar to ptyfs's would be appropriate here.

df(1) gets this right.  hopefully we can use what ever it does
to fix this one...