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

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Message-ID: <20100710101540.2799c9ef@xenia.leun.net>
Date:	Sat, 10 Jul 2010 10:15:40 +0200
From:	Michael Leun <lkml20100708@...ton.leun.net>
To:	Greg KH <greg@...ah.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: sysfs bug when using tun with network namespaces

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).

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 ;-) ).

-- 
MfG,

Michael Leun

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