Kernel panic on RT-N56U with 3.0.3.7-079

[GoogleCodeExporter]

What steps will reproduce the problem?
1. SSH into the router, cd /
2. grep -rHn "support_ipv6_ppe" *

What version of the product are you using? On what operating system?
RT-N56U, 3.0.3.7-079

The router encounters a kernel panic and is automatically restarted by the 
watchdog. There's no room to upload a file, below is the output:

Feb 20 14:38:45 kernel: CPU 0 Unable to handle kernel paging request at virtual 
address c0571b10, epc == c0546edc, ra == c0546e44
Feb 20 14:38:45 kernel: Oops[#1]:
Feb 20 14:38:45 kernel: Cpu 0
Feb 20 14:38:45 kernel: $ 0   : 00000000 2b7fa018 c0571b0c 00000000
Feb 20 14:38:45 kernel: $ 4   : 0002a068 0000540d 0000004a 00000002
Feb 20 14:38:45 kernel: $ 8   : 00000000 80000008 800acad0 fffffff8
Feb 20 14:38:45 kernel: $12   : 4b3d3b04 016e3600 4b3d3b04 016e3600
Feb 20 14:38:45 kernel: $16   : 7fc0f808 0000540d 00000004 00000009
Feb 20 14:38:45 kernel: $20   : 0047b3ec 7fc0fb00 00470050 00000002
Feb 20 14:38:45 kernel: $24   : 00000000 2b82a578                  
Feb 20 14:38:45 kernel: $28   : 86eec000 86eede40 00b0c090 c0546e44
Feb 20 14:38:45 kernel: Hi    : 0000007d
Feb 20 14:38:45 kernel: Lo    : 7d7d7dfa
Feb 20 14:38:45 kernel: epc   : c0546edc 0xc0546edc
Feb 20 14:38:45 kernel:     Tainted: P           
Feb 20 14:38:45 kernel: ra    : c0546e44 0xc0546e44
Feb 20 14:38:45 kernel: Status: 1100ff03    KERNEL EXL IE 
Feb 20 14:38:45 kernel: Cause : 00800008
Feb 20 14:38:45 kernel: BadVA : c0571b10
Feb 20 14:38:45 kernel: PrId  : 0001974c (MIPS 74Kc)
Feb 20 14:38:45 kernel: Modules linked in: rt_timer_wdg usb_storage hw_nat(P) 
nf_nat_ftp nf_conntrack_ftp usblp rt3090_ap(P) rt2860v2_ap(P) ohci_hcd ehci_hcd
Feb 20 14:38:45 kernel: Process grep (pid: 541, threadinfo=86eec000, 
task=86e92958, tls=2b783440)
Feb 20 14:38:45 kernel: Stack : 00470050 00000002 00b0c090 800ab1ec 0000fa00 
00000000 00000000 00000000
Feb 20 14:38:45 kernel:         4a0053f9 000070a5 00b0d658 004a2ca0 01b04dab 
00000004 87f40000 00000000
Feb 20 14:38:45 kernel:         0000540d 8746755c 00000101 7fc0f808 0000540d 
800aca68 00000000 00000000
Feb 20 14:38:45 kernel:         87c0c120 00002000 00000004 800b5ed0 00470050 
00000002 00000004 87f5b000
Feb 20 14:38:45 kernel:         874306e0 874306e8 8746755c 00000020 00000004 
87f5b000 874306e0 8009a010
Feb 20 14:38:45 kernel:         ...
Feb 20 14:38:45 kernel: Call Trace:[<800ab1ec>] 0x800ab1ec
Feb 20 14:38:45 kernel: [<800aca68>] 0x800aca68
Feb 20 14:38:45 kernel: [<800b5ed0>] 0x800b5ed0
Feb 20 14:38:45 kernel: [<8009a010>] 0x8009a010
Feb 20 14:38:45 kernel: [<800acb1c>] 0x800acb1c
Feb 20 14:38:45 kernel: [<80011504>] 0x80011504
Feb 20 14:38:45 kernel: Code: 24427aa4  2ca30013  00821021 <8c440004> 8c420000  
afa4001c  10600027  afa20018  3c02c054 
Feb 20 14:38:45 kernel: ---[ end trace 512d35592e2d19e5 ]---

Original issue reported on code.google.com by d.c.d...@gmail.com on 20 Feb 2014 at 9:44

[GoogleCodeExporter]

DLNA? Base? Aria? Your own flavour?

Original comment by kitch2400 on 21 Feb 2014 at 2:01

[GoogleCodeExporter]

Base, with 6in4 tunneling, OpenVPN, and DDNS configured.

Original comment by d.c.d...@gmail.com on 21 Feb 2014 at 7:49

[GoogleCodeExporter]

Building now, will post results later on.

Original comment by kitch2400 on 22 Feb 2014 at 4:22

[GoogleCodeExporter]

Hmm.

I issued grep -rHn "support_ipv6_ppe" * from / with version 3.4.3.7-075 (on my 
custom build, 3.4.77, RT-N56U). Output: "grep: dev/log: No such device or 
address" and -> crash. Nothing relevant outputs to syslog, but you can verify 
with 'uptime' that there's an actual reboot. Same thing with watchdog enabled 
or disabled.

Lets try it on the newer build then.

grep -rHn "support_ipv6_ppe" * from / with version 3.4.3.7-079 (custom build, 
3.4.79). Output "grep: dev/log: No such device or address".

Device hangs, nothing is logged in syslog, and the device reboots. Same thing 
w. watchdog enabled or disabled.

What's your expected output?

/Kitch

Original comment by kitch2400 on 23 Feb 2014 at 3:25

[GoogleCodeExporter]

I was actually looking around to see what sets the "support_ipv6_ppe" 
configuration option, so the expected output would be the file(s) that contain 
that setting, or alternatively no output if that string doesn't appear in any 
file on the filesystem.

Original comment by d.c.d...@gmail.com on 23 Feb 2014 at 5:52