kern/52029: panic: trap: /etc/rc.d/sysctl start (set mtudisctimeout)

[kardel%netbsd.org@localhost]

>Number:         52029
>Category:       kern
>Synopsis:       sysctl -w  net.inet.ip.mtudisctimeout=600 can panic
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Mar 04 17:00:00 +0000 2017
>Originator:     Frank Kardel
>Release:        NetBSD 7.99.64
>Organization:
	
>Environment:
System: NetBSD pip.kardel.name 7.99.64 NetBSD 7.99.64 (PIPGEN) #8: Sat Mar 4 15:21:09 CET 2017 kardel%pip.kardel.name@localhost:/fs/raid2a/src/NetBSD/cur/src/obj.amd64/sys/arch/amd64/compile/PIPGEN amd64
Architecture: x86_64
Machine: amd64
>Description:
	System panics at startup during /etc/rc.d/sysctl start.
	node to be set is net.inet.ip.mtudisctimeout.
	This is a regression compared to 7.99.42 or later.

	Stacktrace:
#0  0xffffffff8021a045 in cpu_reboot (howto=howto@entry=260, bootstr=bootstr@entry=0x0) at /fs/raid2a/src/NetBSD/cur/src/sys/arch/amd64/amd64/machdep.c:674
#1  0xffffffff809888fc in vpanic (fmt=fmt@entry=0xffffffff810d6eba "trap", ap=ap@entry=0xfffffe813af15a68) at /fs/raid2a/src/NetBSD/cur/src/sys/kern/subr_prf.c:342
#2  0xffffffff809889b0 in panic (fmt=fmt@entry=0xffffffff810d6eba "trap") at /fs/raid2a/src/NetBSD/cur/src/sys/kern/subr_prf.c:258
#3  0xffffffff8021bc92 in trap (frame=0xfffffe813af15ba0) at /fs/raid2a/src/NetBSD/cur/src/sys/arch/amd64/amd64/trap.c:298
#4  0xffffffff8020115e in alltraps ()
#5  0xffffffff80a4cab4 in rt_timer_queue_change (rtq=0x0, timeout=600) at /fs/raid2a/src/NetBSD/cur/src/sys/net/route.c:1720
#6  0xffffffff806898b0 in sysctl_net_inet_ip_pmtudto (name=0xfffffe813af15e50, namelen=0, oldp=0x7f7fff6218dc, oldlenp=0xfffffe813af15e38, newp=0x7f7fff6218d8, newlen=4, oname=0xfffffe813af15e40, l=0xfffffe8826aa1a80,
    rnode=0xfffffe813a6603d0) at /fs/raid2a/src/NetBSD/cur/src/sys/netinet/ip_input.c:1618
#7  0xffffffff80965d92 in sysctl_dispatch (name=name@entry=0xfffffe813af15e40, namelen=<optimized out>, oldp=0x7f7fff6218dc, oldlenp=oldlenp@entry=0xfffffe813af15e38, newp=0x7f7fff6218d8, newlen=4, oname=oname@entry=0xfffffe813af15e40,
    l=l@entry=0xfffffe8826aa1a80, rnode=0xfffffe813a6603d0, rnode@entry=0x0) at /fs/raid2a/src/NetBSD/cur/src/sys/kern/kern_sysctl.c:454
#8  0xffffffff80965fde in sys___sysctl (l=0xfffffe8826aa1a80, uap=0xfffffe813af15f00, retval=<optimized out>) at /fs/raid2a/src/NetBSD/cur/src/sys/kern/kern_sysctl.c:310
#9  0xffffffff8023f705 in sy_call (rval=0xfffffe813af15eb0, uap=0xfffffe813af15f00, l=0xfffffe8826aa1a80, sy=0xffffffff8147ecd0 <sysent+4848>) at /fs/raid2a/src/NetBSD/cur/src/sys/sys/syscallvar.h:65
#10 sy_invoke (code=202, rval=0xfffffe813af15eb0, uap=0xfffffe813af15f00, l=0xfffffe8826aa1a80, sy=0xffffffff8147ecd0 <sysent+4848>) at /fs/raid2a/src/NetBSD/cur/src/sys/sys/syscallvar.h:94
#11 syscall (frame=0xfffffe813af15f00) at /fs/raid2a/src/NetBSD/cur/src/sys/arch/x86/x86/syscall.c:156
#12 0xffffffff80200771 in Xsyscall ()
	ip_mtudisc_timeout_q is NULL at sysctl time. rt_timer_queue_change trips over the NULL-pointer

>How-To-Repeat:
	Take 7.99.64 of 20170304. Try to set mtu discovery timeout during boot time.
>Fix:
	Allocate ip_mtudisc_timeout_q before attemting to set the timeout value.