kern/176401: page fault in netgraph

[Cedric Tabary]

>Number:         176401
>Category:       kern
>Synopsis:       page fault  in netgraph
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sun Feb 24 22:00:00 UTC 2013
>Closed-Date:
>Last-Modified:
>Originator:     Cedric Tabary
>Release:        9.1-STABLE from Sun Jan 13
>Organization:
>Environment:
9.1-STABLE FreeBSD 9.1-STABLE #7: Sun Jan 13 01:00:36 CET 2013 
>Description:
Fatal trap 12: page fault while in kernel mode
cpuid = 4; apic id = 04
fault virtual address   = 0x28
fault code     = supervisor read data, page not present
instruction pointer  = 0x20:0xffffffff81641908
stack pointer          = 0x28:0xffffff8121a580d0
frame pointer          = 0x28:0xffffff8121a58110
code segment      = base 0x0, limit 0xfffff, type 0x1b
         = DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags  = interrupt enabled, resume, IOPL = 0
current process      = 897 (ng_queue4)
trap number    = 12
panic: page fault
cpuid = 4
KDB: stack backtrace:
#0 0xffffffff808e4866 at kdb_backtrace+0x66
#1 0xffffffff808ae7ee at panic+0x1ce
#2 0xffffffff80bc6390 at trap_fatal+0x290
#3 0xffffffff80bc66c8 at trap_pfault+0x1e8
#4 0xffffffff80bc6cce at trap+0x3be
#5 0xffffffff80bb046f at calltrap+0x8
#6 0xffffffff81659254 at ng_tcpmss_rcvdata+0x1e4
#7 0xffffffff81642ca0 at ng_apply_item+0x220
#8 0xffffffff81641efe at ng_snd_item+0x2ce
#9 0xffffffff81654847 at ng_ppp_rcvdata_decompress+0x97
#10 0xffffffff81642ca0 at ng_apply_item+0x220
#11 0xffffffff81641efe at ng_snd_item+0x2ce
#12 0xffffffff81642ca0 at ng_apply_item+0x220
#13 0xffffffff81641efe at ng_snd_item+0x2ce
#14 0xffffffff81655418 at ng_ppp_rcvdata+0x1b8
#15 0xffffffff81642ca0 at ng_apply_item+0x220
#16 0xffffffff81641efe at ng_snd_item+0x2ce
#17 0xffffffff81642ca0 at ng_apply_item+0x220

sysctl.conf contains :

kern.maxusers=512
net.inet.ip.forwarding=1
net.inet6.ip6.forwarding=1
net.inet.ip.redirect=0
net.inet.icmp.drop_redirect=1
net.inet6.ip6.redirect=0
net.inet.flowtable.enable=0
kern.maxfiles=65536
kern.maxfilesperproc=32768

kern.ipc.maxsockbuf=16777216
kern.ipc.nmbclusters=262144
kern.ipc.somaxconn=32768   
kern.ipc.maxsockets=204800

net.graph.maxdgram=2096000
net.graph.recvspace=2096000
net.graph.maxalloc=65536
net.graph.maxdata=65536

kern.random.sys.harvest.ethernet=0
kern.random.sys.harvest.point_to_point=0
kern.random.sys.harvest.interrupt=0
net.route.netisr_maxqlen=2048

>How-To-Repeat:
This is a vpn server (pptp) using mpd with about 130 simultaneous connections.

Crash occurs on 10 servers randomly once or twice a month on each one.
>Fix:


>Release-Note:
>Audit-Trail:
>Unformatted: