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From: Eric W. Biederman on 4 Aug 2010 18:10
Greg KH <greg(a)kroah.com> writes:

> On Wed, Aug 04, 2010 at 03:35:43PM +0200, Michael Leun wrote:
>> Hi,
>>
>> On Sun, 11 Jul 2010 19:29:39 +0200
>> Michael Leun <lkml20100708(a)newton.leun.net> wrote:
>>
>> [...]
>> > Jul 10 20:02:36 doris kernel: unregister_netdevice: waiting for lo to
>> > become free. Usage count = 3 [repeated]

Does this repeat indefinitely, or are there only a couple of repetitions?
If this repeats indefinitely every 5 seconds or so we have a serious bug.

Otherwise we just have cleanup taking longer than it should, which isn't
ideal but it is much less severe.

>> > Now one might say it is fault of openvpn (used OpenVPN 2.1_rc20
>> > i586-suse-linux - the one in openSuSE 11.2 package), openvpn didn't
>> > close some ressource and ssh does fine.
>> >
>> > But: should'nt kernel clean up after process when it exits?
>> > And/or: Should'nt kernel clean up if last process in network namespace
>> > exits - there is nothing left which might use that interface?!
>> >
>> > Greg KH <greg(a)kroah.com> wrote:
>> >
>> > > Yes, you are correct. Care to resend all of this to the
>> > > network-namespace developer(s) and the netdev mailing list so that
>> > > the correct people are notified so they can fix it all?
>> >
>> > [X] done - hopefully, cannot find a particular network namespace
>> > developer in MAINTAINERS or source files. If such a one exists, please
>> > forward.
>>
>> Did'nt work. Got no reaction from network mailinglist at all and bug
>> still is in 2.6.35.
>
> Eric, here's a bug with the network namespace stuff, care to work on
> resolving it?

Greg thanks for forwarding this in my direction.

Eric
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From: Eric W. Biederman on 5 Aug 2010 06:00
Michael Leun <lkml20100708(a)newton.leun.net> writes:

> Hi,
>
> On Wed, 04 Aug 2010 17:12:29 -0700
> ebiederm(a)xmission.com (Eric W. Biederman) wrote:
>
> First, thank you very much for picking that up (and, of course, for
> your work at linux in general).
>
>
>> > # > unshare -n /bin/bash
>> > # > # how to setup veth device pair to get connectivity into
>> > namespace not shown here # > openvpn --config some.config
>> > [ running some traffic over vpn device not shown here ]
>> > ^c # stopping openvpn
>> > # > lsof -i
>> > # > netstat -an
>> > Active Internet connections (servers and established)
>> > Proto Recv-Q Send-Q Local Address Foreign Address
>> > State Active UNIX domain sockets (servers and established)
>> > Proto RefCnt Flags Type State I-Node Path
>> > # > ps ax|grep openvpn|grep -v grep
>> > # > # cannot find anything that suggests there is anything left
>> > from that openvpn session # > exit # logging out from shell in
>> > network namespace
>> >
>> > Now I get
>> >
>> > Jul 10 20:02:36 doris kernel: unregister_netdevice: waiting for lo
>> > to become free. Usage count = 3 [repeated]
>>
>> How many times?
>
> Unfortunately looks like indefinitely. Never watched longer so far
> (rebooted soon), but I'm seeing this message now repeated every 10 secs
> for ~10 minutes on a idle system.

Ugh. A real bug then. These can be a pain to track down and fix. I
think the last one of these I tracked down took a couple of weeks. I
will start digging in when I get back from vacation.

> Additionally when testing this I found another one (by accident started
> my firewall script in that namespace...) - using netfilter RECENT
> makes it barf. Stripped down to the essentials it looks like this:

Micheal this is on 2.6.35?

Alexey can you look at this BUG_ON? It looks like there has been a regression
or you missed something when you did the netns conversion of xt_recent.


>> # unshare -n /bin/bash
>> # iptables -I INPUT -d 1.2.3.4 -m recent --name BLA --set
>> # exit
>
> Aug 5 11:19:47 doris kernel: [ 218.420238] ------------[ cut here ]------------
> Aug 5 11:19:47 doris kernel: [ 218.420256] kernel BUG at net/netfilter/xt_recent.c:609!
> Aug 5 11:19:47 doris kernel: [ 218.420268] invalid opcode: 0000 [#1] PREEMPT SMP
> Aug 5 11:19:47 doris kernel: [ 218.420284] last sysfs file: /sys/devices/LNXSYSTM:00/LNXSYBUS:00/PNP0C0A:00/power_supply/BAT0/charge_full
> Aug 5 11:19:47 doris kernel: [ 218.420295] Modules linked in: snd_pcm_oss snd_mixer_oss snd_seq snd_seq_device edd cpufreq_conservative cpufreq_userspace cpufreq_powersave acpi_cpufreq mperf ipt_REJECT ipt_LOG xt_limit xt_recent iptable_mangle iptable_nat iptable_filter nf_conntrack_ipv6 xt_state xt_tcpudp ip6table_filter ip6_tables nf_nat_ftp nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_conntrack_ftp nf_conntrack ip_tables x_tables fuse nls_utf8 loop arc4 ecb iwlagn iwlcore mac80211 snd_hda_codec_realtek snd_hda_intel snd_hda_codec snd_hwdep snd_pcm cfg80211 snd_timer snd usb_storage iTCO_wdt soundcore tg3 sg iTCO_vendor_support snd_page_alloc rfkill i2c_i801 pcspkr battery ac ext4 jbd2 crc16 sha256_generic aes_generic cbc dm_crypt linear i915 drm_kms_helper drm i2c_algo_bit sd_mod video intel_agp button dm_snapshot dm_mod fan processor ata_piix ahci libahci libata scsi_mod thermal thermal_sys
> Aug 5 11:19:47 doris kernel: [ 218.420529]
> Aug 5 11:19:47 doris kernel: [ 218.420542] Pid: 13, comm: netns Not tainted 2.6.35 #2 Kuril /40684JG
> Aug 5 11:19:47 doris kernel: [ 218.420557] EIP: 0060:[<fc886a15>] EFLAGS: 00010206 CPU: 0
> Aug 5 11:19:47 doris kernel: [ 218.420578] EIP is at recent_net_exit+0x55/0x70 [xt_recent]
> Aug 5 11:19:47 doris kernel: [ 218.420589] EAX: f2218000 EBX: f5b79290 ECX: f2f27b40 EDX: f5cd4000
> Aug 5 11:19:47 doris kernel: [ 218.420601] ESI: f2218000 EDI: f5cd5f44 EBP: f5cd5f28 ESP: f5cd5f20
> Aug 5 11:19:47 doris kernel: [ 218.420612] DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068
> Aug 5 11:19:47 doris kernel: [ 218.420626] Process netns (pid: 13, ti=f5cd4000 task=f5cc9920 task.ti=f5cd4000)
> Aug 5 11:19:47 doris kernel: [ 218.420635] Stack:
> Aug 5 11:19:47 doris kernel: [ 218.420641] f5cd5f30 fc887618 f5cd5f3c c130867d fc887618 f5cd5f44 c1308850 f5cd5f60
> Aug 5 11:19:47 doris kernel: [ 218.420667] <0> c1308919 f2218014 f2218014 f221800c f221800c c15915a0 c3bb4f40 c1308850
> Aug 5 11:19:47 doris kernel: [ 218.420695] <0> f5cd5fbc c105a230 c13d1658 00000001 00000000 f7048000 c160f500 f5cc9c00
> Aug 5 11:19:47 doris kernel: [ 218.420724] Call Trace:
> Aug 5 11:19:47 doris kernel: [ 218.420749] [<c130867d>] ? ops_exit_list+0x1d/0x50
> Aug 5 11:19:47 doris kernel: [ 218.420766] [<c1308850>] ? cleanup_net+0x0/0x160
> Aug 5 11:19:47 doris kernel: [ 218.420782] [<c1308919>] ? cleanup_net+0xc9/0x160
> Aug 5 11:19:47 doris kernel: [ 218.420797] [<c1308850>] ? cleanup_net+0x0/0x160
> Aug 5 11:19:47 doris kernel: [ 218.420815] [<c105a230>] ? worker_thread+0x110/0x250
> Aug 5 11:19:47 doris kernel: [ 218.420832] [<c13d1658>] ? schedule+0x748/0x7a0
> Aug 5 11:19:47 doris kernel: [ 218.420849] [<c105d5f0>] ? autoremove_wake_function+0x0/0x40
> Aug 5 11:19:47 doris kernel: [ 218.420864] [<c105a120>] ? worker_thread+0x0/0x250
> Aug 5 11:19:47 doris kernel: [ 218.420879] [<c105d1bc>] ? kthread+0x6c/0x80
> Aug 5 11:19:47 doris kernel: [ 218.420895] [<c105d150>] ? kthread+0x0/0x80
> Aug 5 11:19:47 doris kernel: [ 218.420910] [<c1003336>] ? kernel_thread_helper+0x6/0x10
> Aug 5 11:19:47 doris kernel: [ 218.420919] Code: 91 08 89 e2 81 e2 00 e0 ff ff 83 6a 14 01 f6 42 08 08 75 19 3b 1b 75 13 ba fa 72 88 fc e8 94 3e 8c c4 8d 64 24 04 5b 5d c3 0f 0b <0f> 0b 89 45 f8 e8 a1 ad b4 c4 8b 45 f8 eb da 8d b6 00 00 00 00
> Aug 5 11:19:47 doris kernel: [ 218.421063] EIP: [<fc886a15>] recent_net_exit+0x55/0x70 [xt_recent] SS:ESP 0068:f5cd5f20
> Aug 5 11:19:47 doris kernel: [ 218.421136] ---[ end trace f57524f15f4df616 ]---
>


Eric
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