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Subject[PATCH] vlan:return error when real dev is enslaved
Qinhuibin reported a kernel panic when he do some operation about vlan.

The operation is as below:
ifconfig eth2 up
modprobe bonding
modprobe 8021q
ifconfig bond0 up
ifenslave bond0 eth2
vconfig add eth2 3300
vconfig add bond0 33
vconfig rem eth2.3300

the panic stack is as below:
[<ffffffffa002f1c9>] panic_event+0x49/0x70 [ipmi_msghandler]
[<ffffffff80378917>] notifier_call_chain+0x37/0x70
[<ffffffff80372122>] panic+0xa2/0x195
[<ffffffff80376ed8>] oops_end+0xd8/0x140
[<ffffffff8001bea7>] no_context+0xf7/0x280
[<ffffffff8001c1a5>] __bad_area_nosemaphore+0x175/0x250
[<ffffffff80376318>] page_fault+0x28/0x30
[<ffffffffa039dabd>] igb_vlan_rx_kill_vid+0x4d/0x100 [igb]
[<ffffffffa044045f>] bond_vlan_rx_kill_vid+0x9f/0x290 [bonding]
[<ffffffffa047e636>] unregister_vlan_dev+0x136/0x180 [8021q]
[<ffffffffa047ed20>] vlan_ioctl_handler+0x170/0x3f0 [8021q]
[<ffffffff802c1d3f>] sock_ioctl+0x21f/0x280
[<ffffffff800e6d7f>] vfs_ioctl+0x2f/0xb0
[<ffffffff800e726b>] do_vfs_ioctl+0x3cb/0x5a0
[<ffffffff800e74e1>] sys_ioctl+0xa1/0xb0
[<ffffffff80007388>] system_call_fastpath+0x16/0x1b
[<00007f108a2b8bd7>] 0x7f108a2b8bd7
And the nic is as below:
[root@localhost ~]# ethtool -i eth2
driver: igb
version: 3.0.6-k2
firmware-version: 1.2-1
bus-info: 0000:04:00.0
kernel version: also happen in 2.6.32-131

For kernel 2.6.32, the reason of this bug is that when we do "vconfig add bond0 33",
adapter->vlgrp is overwritten in igb_vlan_rx_register. So when we do "vconfig rem
eth2.3300", it can't find the correct vlgrp.

And this bug is avoided by vlan cleanup patchset from Jiri Pirko
<>, especially commit b2cb09b1a772(igb: do vlan cleanup).

But it is not a correct operation to creat a vlan interface on eth2
when it have been enslaved by bond0, so this patch is to return error
when the real dev is already enslaved.

Signed-off-by: Weiping Pan <>
net/8021q/vlan.c | 5 +++++
1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/net/8021q/vlan.c b/net/8021q/vlan.c
index 5471628..8ba9226 100644
--- a/net/8021q/vlan.c
+++ b/net/8021q/vlan.c
@@ -148,6 +148,11 @@ int vlan_check_real_dev(struct net_device *real_dev, u16 vlan_id)
const char *name = real_dev->name;
const struct net_device_ops *ops = real_dev->netdev_ops;

+ if (real_dev->flags & IFF_SLAVE) {
+ pr_info("Error, %s was already enslaved\n", name);
+ return -EOPNOTSUPP;
+ }
if (real_dev->features & NETIF_F_VLAN_CHALLENGED) {
pr_info("VLANs not supported on %s\n", name);
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