[BUG - v3.10.27] sit: Bad list pointer

[Steven Rostedt]

On 3.10.27, loading and then unloading the sit module gives me the
following bug:

[   35.400878] sit: IPv6 over IPv4 tunneling driver
[   36.959308] ------------[ cut here ]------------
[   36.963983] WARNING: at /home/rostedt/work/git/linux-rt.git/lib/list_debug.c:59 __list_del_entry+0xa1/0xd0()
[   36.973874] list_del corruption. prev->next should be ffff88011656d070, but was ffff880115fe5ea8
[   36.982684] Modules linked in: sit(-) ip_tunnel tunnel4 bnep lockd bluetooth nf_conntrack_ipv4 ip6t_REJECT nf_defrag_ipv4 nf_conntrack_ipv6 nf_defrag_ipv6 xt_state nf_conntrack ip6table_filter ip6_tables snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_intel snd_hda_codec tpm_infineon snd_hwdep hp_wmi rfkill tpm_tis tpm coretemp snd_seq lpc_ich snd_seq_device snd_pcm sparse_keymap uinput serio_raw pcspkr mfd_core tpm_bios i2c_i801 microcode wmi snd_page_alloc snd_timer snd soundcore i915 e1000e i2c_algo_bit ptp drm_kms_helper crc32c_intel drm pps_core i2c_core video sunrpc
[   37.034430] CPU: 0 PID: 1071 Comm: rmmod Not tainted 3.10.27-test #143
[   37.040972] Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v02.05 05/07/2012
[   37.049962]  ffffffff81a10e78 ffff880115fe5d18 ffffffff8161b3c7 ffff880115fe5d58
[   37.057439]  ffffffff8104b2a0 ffff880115fe5dd8 ffff880115fe5df8 ffff88011656d070
[   37.064911]  0000000000000080 0000000000000018 ffff880115cb4000 ffff880115fe5db8
[   37.072405] Call Trace:
[   37.074869]  [<ffffffff8161b3c7>] dump_stack+0x19/0x1b
[   37.080031]  [<ffffffff8104b2a0>] warn_slowpath_common+0x70/0xa0
[   37.086051]  [<ffffffff8104b386>] warn_slowpath_fmt+0x46/0x50
[   37.091814]  [<ffffffff812f56a1>] __list_del_entry+0xa1/0xd0
[   37.097491]  [<ffffffff815168a5>] unregister_netdevice_queue+0x35/0xa0
[   37.104036]  [<ffffffffa038df82>] sit_exit_net+0xc2/0xf0 [sit]
[   37.109893]  [<ffffffff81511278>] ops_exit_list.isra.4+0x38/0x60
[   37.115917]  [<ffffffff815113d0>] unregister_pernet_operations+0x70/0xb0
[   37.122633]  [<ffffffff8151143e>] unregister_pernet_device+0x2e/0x60
[   37.129005]  [<ffffffffa038f86f>] sit_cleanup+0x2d/0x7be [sit]
[   37.134864]  [<ffffffff810b0aee>] SyS_delete_module+0x19e/0x2a0
[   37.140801]  [<ffffffff8162983b>] tracesys+0xdd/0xe2
[   37.145779] ---[ end trace e45e22e840e55d00 ]---
[   37.150427] ------------[ cut here ]------------

Investigating differences between 3.10.27 and newer kernels, I found
that the below change is not there. It was part of commit 205983c43700
"sit: allow to use rtnl ops on fb tunnel" which happens to be
backported to 3.10 but in 3.10 backport commit 20300db1bd1b9 this part
of the commit is missing.

When I add this change, the removing of the module no longer gives this
bug.

Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>

diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
index 0491264..02300e8 100644
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -1592,7 +1592,6 @@ static void __net_exit sit_exit_net(struct net *net)
 
 	rtnl_lock();
 	sit_destroy_tunnels(sitn, &list);
-	unregister_netdevice_queue(sitn->fb_tunnel_dev, &list);
 	unregister_netdevice_many(&list);
 	rtnl_unlock();
 }
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