kern/55182: NPF on NetBSD 9 can lock / panic machine

[john%ziaspace.com@localhost]

>Number:         55182
>Category:       kern
>Synopsis:       NPF on NetBSD 9 can lock / panic machine
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Apr 15 17:00:01 +0000 2020
>Originator:     John Klos
>Release:        NetBSD 9.0_STABLE
>Organization:
	
>Environment:
	
	
System: NetBSD athena.zia.io 9.0_STABLE NetBSD 9.0_STABLE (ATHENA-$Revision: 9.0q $) #1: Fri Apr 10 06:29:38 UTC 2020 john%athena.zia.io@localhost:/home/obj-alpha/sys/arch/alpha/compile/ATHENA alpha
Architecture: alpha
Machine: alpha
>Description:
	
NPF on NetBSD 9 has caused a direct panic on Alpha and a complete lockup
on amd64 by running:

echo "199.233.217.205" >> /etc/npf_blacklist ; /etc/rc.d/npf reload

The panic on Alpha gave:

[ 4656449.519341] CPU 0: fatal kernel trap:

[ 4656449.521294] CPU 0    trap entry = 0x2 (memory management fault)
[ 4656449.522270] CPU 0    a0         = 0x0
[ 4656449.523247] CPU 0    a1         = 0x1
[ 4656449.524224] CPU 0    a2         = 0x0
[ 4656449.525200] CPU 0    pc         = 0xfffffc0000bc9048
[ 4656449.526177] CPU 0    ra         = 0xfffffc0000bc2d0c
[ 4656449.527153] CPU 0    pv         = 0xfffffc0000bc9030
[ 4656449.528130] CPU 0    curlwp     = 0xfffffc0150c7c580
[ 4656449.529106] CPU 0        pid = 29135, comm = npfctl

[ 4656449.531059] panic: trap

The amd64 system had to be power cycled (it is remote).

On other amd64 NetBSD 9 systems, I have observed:

Plenty of NAT traffic, fine.
Tons of network connections and work, fine.
Both together, I can lock up a machine pretty reliably within an hour.

One issue is that even when I've had this happen locally, I cannot get 
in to the kernel debugger on amd64 after a lockup.

The configurations are essentially the same as in the NPF documentation.
This is both with GENERIC kernels and with kernels with NPF compiled in.

>How-To-Repeat:
	

Set up a machine to do NAT via NPF for a somewhat busy network using the 
example configurations in the NPF documentation.

While the network is reasonably busy, either make changes to NPF and run
"/etc/rc.d/npf reload", or create lots of network traffic on the machine 
running NPF. There will be a non-trivial chance of lockup or panic.

>Fix:
	

>Unformatted: