linux-kernel - Re: sysfs bug when using tun with network namespaces

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Date:	Sat, 10 Jul 2010 07:08:00 -0700
From:	Greg KH <greg@...ah.com>
To:	Michael Leun <lkml20100708@...ton.leun.net>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: sysfs bug when using tun with network namespaces

On Sat, Jul 10, 2010 at 10:15:40AM +0200, Michael Leun wrote:
> Hi,
> 
> On Fri, 9 Jul 2010 16:57:44 -0700
> Greg KH <greg@...ah.com> wrote:
> 
> > On Thu, Jul 08, 2010 at 04:40:09PM +0000, Michael Leun wrote:
> > > Hello,
> > > 
> > > > # tunctl -u ml -t tap1
> > > 
> > > works as expected, but
> > > 
> > > > # unshare -n /bin/bash
> > > > # tunctl -u ml -t tap1
> > > 
> > > Jul  8 18:03:59 doris kernel: ------------[ cut here ]------------
> > > Jul  8 18:03:59 doris kernel: kernel BUG at fs/sysfs/file.c:540!
> > > Jul  8 18:03:59 doris kernel: invalid opcode: 0000 [#1] PREEMPT SMP 
> > > Jul  8 18:03:59 doris kernel: last sysfs
> > > file: /sys/devices/virtual/misc/tun/dev Jul  8 18:03:59 doris
> > > kernel: Modules linked in: tun snd_pcm_oss snd_mixer_oss snd_seq
> > > snd_seq_device vboxnetadp vboxnetflt vboxdrv ipv6
> > > cpufreq_conservative cpufreq_ondemand cpufreq_userspace
> > > cpufreq_powersave acpi_cpufreq speedstep_lib freq_table ipt_REJECT
> > > ipt_LOG xt_limit xt_recent xt_state xt_tcpudp iptable_mangle
> > > iptable_nat iptable_filter nf_nat_ftp nf_nat nf_conntrack_ipv4
> > > nf_defrag_ipv4 nf_conntrack_ftp nf_conntrack ip_tables x_tables
> > > fuse nls_utf8 loop snd_hda_codec_realtek arc4 snd_hda_intel ecb
> > > snd_hda_codec iwlagn snd_pcm iwlcore snd_timer mac80211 snd
> > > cfg80211 soundcore intel_agp video usb_storage agpgart i2c_i801
> > > rfkill snd_page_alloc output button battery ac joydev sg evdev tg3
> > > edd ext4 jbd2 crc16 sha256_generic aes_i586 aes_generic cbc
> > > dm_crypt linear rtc_cmos uhci_hcd rtc_core rtc_lib sd_mod
> > > crc_t10dif ehci_hcd usbcore dm_snapshot dm_mod fan processor
> > > thermal [last unloaded: tun] Jul  8 18:03:59 doris kernel: Jul  8
> > > 18:03:59 doris kernel: Pid: 4320, comm: tunctl Not tainted 2.6.34.1
> > > #3 Kuril                           /40684JG         
> > 
> > Network namespaces didn't go in until 2.6.35-rc, how is this working
> > on ..34.1?
> 
> Huh? Network namespaces were there for quite some time - just for fun I
> grabbed a random older kernel (got 2.6.27.48) to check. CONFIG NET_NS
> was also in there (but was defined in net/Kconfig and had a depency
> on !SYSFS).

Ah, yeah, but everyone used SYSFS so it probably was never used :)

> In 2.6.34 it is defined in init/Kconfig (and has no depency on SYSFS at
> all).
> 
> I think I started actually using that somewhere between .30 and .32.
> 
> > Can you verify this works properly in .35-rc4?
> 
> Indeed, it works there.
> 
> There are several differencies between 2.6.34.1 and 2.6.35-rc4 in
> fs/sysfs/* stuff as well as in e.g. net/core/net_namespaces.c.
> 
> I'll bisect that (but not on this atom netbook I used so far ;-) ).

I'd not recommend using it until .35-rc because of the sysfs changes
required.

sorry,

greg k-h
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