[FS#607] Kernel BUG: Bad page state in process ntpd-hotplug

[LEDE Bugs]

A new Flyspray task has been opened.  Details are below. 

User who did this - Baptiste Jonglez (bjonglez) 

Attached to Project - LEDE Project
Summary - Kernel BUG: Bad page state in process ntpd-hotplug
Task Type - Bug Report
Category - Kernel
Status - New
Assigned To - 
Operating System - All
Severity - Low
Priority - Medium
Reported Version - Trunk
Due in Version - Undecided
Due Date - Undecided
Details - While doing wireless benchmarks between two TP-Link WR841 running the latest LEDE, one of them (the AP) showed the stack trace below.  It does not seem to impact the behaviour of the system, though: everything seems to work correctly after the stack trace.

The device is TL-WR841N v8, with a snapshot build r3670-154b3a6 (kernel is 4.4.52).

It occurred about one minute after I plugged the WAN port to the Internet, which explains why ntpd-hotplug appears in the log. There was still a heavy amount of wireless traffic (both when I plugged the WAN, and when the stack trace occurred).  


Wed Mar  8 22:02:31 2017 kern.alert kernel: [ 1913.427453] BUG: Bad page state in process ntpd-hotplug  pfn:015fa
Wed Mar  8 22:02:31 2017 kern.emerg kernel: [ 1913.433936] page:8102bf40 count:-2130657536 mapcount:16711936 mapping:  (null) index:0xff00ff00
Wed Mar  8 22:02:31 2017 kern.emerg kernel: [ 1913.442939] flags: 0x0()
Wed Mar  8 22:02:31 2017 kern.alert kernel: [ 1913.445561] page dumped because: nonzero _count
Wed Mar  8 22:02:31 2017 kern.warn kernel: [ 1913.450237] Modules linked in: ath9k ath9k_common pppoe ppp_async ath9k_hw ath pppox ppp_generic nf_conntrack_ipv6 mac80211 iptable_nat ipt_REJECT ipt_MASQUERADE cfg80211 xt_time xt_tcpudp xt_state xt_nat xt_multiport xt_mark xt_mac xt_limit xt_conntrack xt_comment xt_TCPMSS xt_REDIRECT xt_LOG xt_CT slhc nf_reject_ipv4 nf_nat_redirect nf_nat_masquerade_ipv4 nf_conntrack_ipv4 nf_nat_ipv4 nf_nat nf_log_ipv4 nf_defrag_ipv6 nf_defrag_ipv4 nf_conntrack_rtcache nf_coWed Mar  8 22:02:31 2017 kern.warn kernel: [ 1913.509878] CPU: 0 PID: 1501 Comm: ntpd-hotplug Not tainted 4.4.52 #0
Wed Mar  8 22:02:31 2017 kern.warn kernel: [ 1913.516549] Stack : 803e49f0 00000000 00000001 80440000 818f16a4 8042ee63 803c5ff4 000005dd
Wed Mar  8 22:02:31 2017 kern.warn kernel: [ 1913.516549] 	  804a378c 803d0000 803d0000 803d0000 803d0000 800a7640 803cb6e4 80430000
Wed Mar  8 22:02:31 2017 kern.warn kernel: [ 1913.516549] 	  00000003 803d0000 803c9af0 81809d74 803d0000 800a55bc 803d0000 803d0000
Wed Mar  8 22:02:31 2017 kern.warn kernel: [ 1913.516549] 	  803d0000 801f5800 00000000 00000000 00000000 00000000 00000000 00000000
Wed Mar  8 22:02:31 2017 kern.warn kernel: [ 1913.516549] 	  00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
Wed Mar  8 22:02:31 2017 kern.warn kernel: [ 1913.516549] 	  ...
Wed Mar  8 22:02:31 2017 kern.warn kernel: [ 1913.553574] Call Trace:
Wed Mar  8 22:02:31 2017 kern.warn kernel: [ 1913.556121] [] show_stack+0x50/0x84
Wed Mar  8 22:02:31 2017 kern.warn kernel: [ 1913.560630] [] bad_page+0xec/0x11c
Wed Mar  8 22:02:31 2017 kern.warn kernel: [ 1913.565069] [] free_pages_prepare+0x19c/0x1f8
Wed Mar  8 22:02:31 2017 kern.warn kernel: [ 1913.570474] [] __free_pages_ok+0x2c/0x31c
Wed Mar  8 22:02:31 2017 kern.warn kernel: [ 1913.575554] [] __kfree_skb+0x28/0xb0
Wed Mar  8 22:02:31 2017 kern.warn kernel: [ 1913.580155] [] ag71xx_tx_packets+0x154/0x2c8
Wed Mar  8 22:02:31 2017 kern.warn kernel: [ 1913.585486] [] ag71xx_poll+0x6c/0x5c0
Wed Mar  8 22:02:31 2017 kern.warn kernel: [ 1913.590203] [] net_rx_action+0x10c/0x2c8
Wed Mar  8 22:02:31 2017 kern.warn kernel: [ 1913.595183] [] __do_softirq+0x250/0x298
Wed Mar  8 22:02:31 2017 kern.warn kernel: [ 1913.600066] [] plat_irq_dispatch+0xd4/0x10c
Wed Mar  8 22:02:31 2017 kern.warn kernel: [ 1913.605297] 
Wed Mar  8 22:02:31 2017 kern.warn kernel: [ 1913.606843] Disabling lock debugging due to kernel taint



More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=607