WARNING in xdp_rxq_info_unreg

[syzbot]

Hello,

syzbot hit the following crash on net-next commit
ebdd7b491b8a65d65936e07004caabca4a3c94a0 (Sun Jan 21 23:21:31 2018 +0000)
Merge branch 'mlxsw-Add-support-for-mirror-action-with-flower'

So far this crash happened 52 times on net-next.
C reproducer is attached.
syzkaller reproducer is attached.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.

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------------[ cut here ]------------
Driver BUG
WARNING: CPU: 1 PID: 3661 at net/core/xdp.c:22 xdp_rxq_info_unreg+0xc1/0xf0
net/core/xdp.c:22
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 3661 Comm: syzkaller881172 Not tainted 4.15.0-rc8+ #202
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x194/0x257 lib/dump_stack.c:53
panic+0x1e4/0x41c kernel/panic.c:183
__warn+0x1dc/0x200 kernel/panic.c:547
report_bug+0x211/0x2d0 lib/bug.c:184
fixup_bug.part.11+0x37/0x80 arch/x86/kernel/traps.c:178
fixup_bug arch/x86/kernel/traps.c:247 [inline]
do_error_trap+0x2d7/0x3e0 arch/x86/kernel/traps.c:296
do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315
invalid_op+0x22/0x40 arch/x86/entry/entry_64.S:1096
RIP: 0010:xdp_rxq_info_unreg+0xc1/0xf0 net/core/xdp.c:22
RSP: 0018:ffff8801bc62ee78 EFLAGS: 00010282
RAX: dffffc0000000008 RBX: ffff8801d950b1c0 RCX: ffffffff8159f28e
RDX: 0000000000000000 RSI: 1ffff100378c5d8a RDI: 0000000000000293
RBP: ffff8801bc62ee90 R08: 1ffff100378c5d4c R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801d950b1cc
R13: 0000000000000002 R14: 00000000000003e8 R15: 0000000000000000
tun_cleanup_tx_ring.part.47+0x236/0x450 drivers/net/tun.c:686
tun_cleanup_tx_ring drivers/net/tun.c:684 [inline]
tun_detach_all+0x4fd/0xbf0 drivers/net/tun.c:779
tun_net_uninit+0x15/0x20 drivers/net/tun.c:1003
rollback_registered_many+0x9a8/0xe20 net/core/dev.c:7360
unregister_netdevice_many.part.118+0x87/0x420 net/core/dev.c:8421
unregister_netdevice_many+0xbb/0x100 net/core/dev.c:8420
rtnl_delete_link+0x10f/0x170 net/core/rtnetlink.c:2586
rtnl_dellink+0x2d5/0x7e0 net/core/rtnetlink.c:2625
rtnetlink_rcv_msg+0x57f/0xb10 net/core/rtnetlink.c:4530
netlink_rcv_skb+0x14b/0x380 net/netlink/af_netlink.c:2442
rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:4548
netlink_unicast_kernel net/netlink/af_netlink.c:1308 [inline]
netlink_unicast+0x4c4/0x6b0 net/netlink/af_netlink.c:1334
netlink_sendmsg+0xa4a/0xe60 net/netlink/af_netlink.c:1897
sock_sendmsg_nosec net/socket.c:630 [inline]
sock_sendmsg+0xca/0x110 net/socket.c:640
___sys_sendmsg+0x767/0x8b0 net/socket.c:2020
__sys_sendmsg+0xe5/0x210 net/socket.c:2054
SYSC_sendmsg net/socket.c:2065 [inline]
SyS_sendmsg+0x2d/0x50 net/socket.c:2061
entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x445189
RSP: 002b:00007fff8d14a8c8 EFLAGS: 00000207 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004a6a32 RCX: 0000000000445189
RDX: 0000000020000040 RSI: 000000002001bfc8 RDI: 0000000000000004
RBP: 00007fff8d14a9d8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000207 R12: 00007fff8d14a9d8
R13: 0000000000402650 R14: 0000000000000000 R15: 0000000000000000
Dumping ftrace buffer:
(ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


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[Cong Wang]

This is caused by the merge conflict, I will send a fix.