sh in linux_base cannot write to /dev/null

[Stephen Montgomery-Smith]

I installed linux_base from the ports.  If I then run
/compat/linux/bin/sh
and then type
cat > /dev/null
I get an error message:
sh: /dev/null: Permission denied

Incidently this error doesn't happen with linux_base-8.

I am running FreeBSD-5.3-STABLE and ls -l /dev/null gives
crw-rw-rw-  1 root  wheel    2,   2 Dec 20 12:11 /dev/null


Thanks, Stephen