kern/48464: ping localhost causes a kernel panic

[pooka%iki.fi@localhost]

>Number:         48464
>Category:       kern
>Synopsis:       ping localhost causes a kernel panic
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Dec 20 13:40:00 +0000 2013
>Originator:     pooka%iki.fi@localhost
>Release:        HEAD 201312171040Z/amd64
>Organization:
>Environment:
>Description:

>How-To-Repeat:
python anita interact 
http://nyftp.netbsd.org/pub/NetBSD-daily/HEAD/201312171040Z/amd64/
[...]
# ping localhost
PING localhost (127.0.0.1): 64 data bytes
fatal page fault in supervisor mode
trap type 6 code 0 rip ffffffff80269787 cs 8 rflags 206 cr2 fffffe8040000000 
ilevel 4 rsp fffffe80014a4bb8
curlwp 0xfffffe8007f2b420 pid 0.3 lowest kstack 0xfffffe80014a1000
kernel: page fault trap, code=0
Stopped in pid 0.3 (system) at  netbsd:cpu_in_cksum+0xa7:       movl    4(%rbx),
%eax
db{0}> tr
cpu_in_cksum() at netbsd:cpu_in_cksum+0xa7
fatal page fault in supervisor mode
trap type 6 code 0 rip ffffffff802898f3 cs 8 rflags 246 cr2 a9e8 ilevel 8 rsp 
fffffe80014a3f40
curlwp 0xfffffe8007f2b420 pid 0.3 lowest kstack 0xfffffe80014a1000
kernel: page fault trap, code=0
Faulted in DDB; continuing...
db{0}> 

>Fix: