[LEDE-DEV] Firewall restart crashes routers with kernel 4.14

[Kristian Evensen]

Hello,

When restarting the firewall on routers running latest nightly, I
frequently get the following warning:

[   74.952854] ------------[ cut here ]------------
[   74.952874] WARNING: CPU: 2 PID: 0 at
net/netfilter/nf_conntrack_rtcache.c:197 0x8f6293f0
[   74.952876] Modules linked in: rt2800pci rt2800mmio rt2800lib
qcserial ppp_async option usb_wwan rt2x00pci rt2x00mmio rt2x00lib
rndis_host qmi_wwan ppp_generic nf_nat_pptp nf_conntrack_pptp
nf_conntrack_ipv6p
[   74.953097]  nf_nat_snmp_basic nf_nat_sip nf_nat_redirect
nf_nat_proto_gre nf_nat_masquerade_ipv4 nf_nat_irc nf_conntrack_ipv4
nf_nat_ipv4 nf_nat_h323 nf_nat_ftp nf_nat_amanda nf_nat nf_log_ipv4
nf_flow_tablt
[   74.953279]  ip_set_hash_netiface ip_set_hash_netport
ip_set_hash_netnet ip_set_hash_net ip_set_hash_netportnet
ip_set_hash_mac ip_set_hash_ipportnet ip_set_hash_ipportip
ip_set_hash_ipport ip_set_hash_ipmarm
[   74.953472]  ohci_hcd ehci_platform sd_mod scsi_mod ehci_hcd
gpio_button_hotplug usbcore nls_base usb_common mii
[   74.953512] CPU: 2 PID: 0 Comm: swapper/2 Tainted: G        W
4.14.37 #0
[   74.953515] Stack : 00000000 00000000 00000000 00000000 805c7ad2
00000042 00000000 8052c580
[   74.953542]         8fc44834 805668e7 804f59fc 00000002 00000000
00000001 8fc11c38 00000000
[   74.953569]         00000000 00000000 805c0000 1233d908 00000004
80452cac 7d0b0d06 000c2bff
[   74.953597]         00000000 80570000 0000935d 805f0000 00000000
00000000 80590000 8f6293f0
[   74.953625]         00000009 000000c5 00000001 00000003 00000002
8036a504 00000008 805c0008
[   74.953652]         ...
[   74.953660] Call Trace:
[   74.953674] [<800103f8>] show_stack+0x58/0x100
[   74.953689] [<8043c03c>] dump_stack+0x9c/0xe0
[   74.953700] [<8002e190>] __warn+0xe0/0x114
[   74.953711] [<8002e254>] warn_slowpath_null+0x1c/0x28
[   74.953739] [<8f6293f0>] 0x8f6293f0
[   74.953754] ---[ end trace 6b009cc1611edaa4 ]---

The router then seems to spin on this warning, becomes
unreachable/unresponsive and never reboots. If I compile an image with
rtcache disabled (doing rmmod on the module triggers an oops),
firewall restarts works fine.

I tried to take a look at the code to check if I could spot anything
obvious, but couldn't see anything.

BR,
Kristian