restarting container with a vlan interface results in kernel stack trace

[Lars Heer]

[Impact]
Users of VLANs with LXC containers will see kernel BUGs when starting and stopping containers.

[Test Case]
- In trusty, install lxc and vlan.
- Edit /etc/lxc/default.conf as follows:
    lxc.network.type=vlan
    lxc.network.vlan.id=10
    lxc.network.flags=up
    lxc.network.link=eth0
    lxc.aa_profile = unconfined
- Setup LXC container
    sudo lxc-create -t download -n u1 -- --dist ubuntu --release trusty --arch amd64
- Run the following until you see the failure:
    lxc-start --name u1 -d
    lxc-stop --name u1

[Fix]
commit 5bb025fae53889cc99a21058c5dd369bf8cce820
support patches:
commit 0a59f3a9fd7e2801a445682465ea0522ea497183
commit 3ee32707560955e92d30f7f6e5138cb92a3b1a7e

--

Stopping a container and starting it again results in kernel stack trace with a vlan interface.

---8<---
lxc.network.type = vlan
lxc.network.flags = up
lxc.network.link = p3p1
lxc.network.vlan.id = 2
---8<---

dpkg -l | grep lxc
ii liblxc1 1.0.6-0ubuntu0.1 amd64 Linux Containers userspace tools (library)
ii lxc 1.0.6-0ubuntu0.1 amd64 Linux Containers userspace tools
ii lxc-templates 1.0.6-0ubuntu0.1 amd64 Linux Containers userspace tools (templates)
ii python3-lxc 1.0.6-0ubuntu0.1 amd64 Linux Containers userspace tools (Python 3.x bindings)

cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-3.13.0-44-generic root=UUID=6d1fc9aa-735c-4e61-ae1c-0a9d2587e77b ro acpi_osi=Linux acpi=force acpi_enforce_resources=lax i915.i915_enable_rc6=1 i915.i915_enable_fbc=1 i915.lvds_downclock=1 i915.semaphores=1

Snipplet from stack trace:
---8<---
[35188.374621] WARNING: CPU: 4 PID: 3933 at /build/buildd/linux-3.13.0/fs/sysfs/dir.c:486 sysfs_warn_dup+0x86/0xa0()
[35188.374623] sysfs: cannot create duplicate filename '/devices/pci0000:00/0000:00:1c.3/0000:02:00.0/net/p3p1/upper_vlan2'
---8<---

Is deconfiguration on stop of an lxc instance not working anymore?

[Gunnlaugur Máni Hrólfsson (mani-tungli)]

I have the same problem.

Network config:
--------------
lxc.network.type=vlan
lxc.network.link=eth0
lxc.network.name=eth1
lxc.network.vlan.id = 3575
lxc.network.flags=up
--------------

From stack trace:
----------------
[63371.593308] WARNING: CPU: 6 PID: 10623 at /build/buildd/linux-lts-trusty-3.13.0/fs/sysfs/dir.c:486 sysfs_warn_dup+0x91/0xb0()
[63371.593310] sysfs: cannot create duplicate filename '/devices/pci0000:00/0000:00:06.0/0000:03:00.0/0000:04:00.0/net/eth0/upper_vlan3575'
---------------

It seems to be a problem with the kernel. This is the kernel version on this host:
# uname -r
3.13.0-32-generic

I have another host with the same lxc version. But with a different kernel that doesn't have this problem:
# uname -r
3.5.0-39-generic

[Lars Heer (l-heer)]

Installation of kernel 3.16 (of course with boot option intel_pstate=disable) fixed the problem.

[Brad Figg (brad-figg)]

This bug is missing log files that will aid in diagnosing the problem. From a terminal window please run:

apport-collect 1410852

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Chris J Arges (arges)]

I can easily reproduce this issue.
Tested with 3.16 mainline kernel and this did not occur. I can begin a bisect tomorrow, or test any proposals.

[Brad Figg (brad-figg)]

This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-trusty' to 'verification-done-trusty'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Seth Forshee (sforshee)]

Bug is easily reproducible with 3.13.0-48, cannot reproduce in 3.13.0-49. Marking as verified for trusty.

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux - 3.13.0-49.81

---------------
linux (3.13.0-49.81) trusty; urgency=low

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