Hello,

syzbot hit the following crash on net-next commit
1ec010e705934c8acbe7dbf31afc81e60e3d828b (Fri Feb 16 10:03:07 2018 +0000)
tun: export flags, uid, gid, queue information over netlink

So far this crash happened 2 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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Reported-by: syzbot+f62e0f2a0ef578703946@syzkaller.appspotmail.com
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Subscription rejected, no memory
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
    (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 4074 Comm: syzkaller787570 Not tainted 4.16.0-rc1+ #231
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:tipc_conn_close+0x4c/0x130 net/tipc/topsrv.c:165
RSP: 0018:ffff8801d82a78e8 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffff8801c5f54580 RCX: ffffffff856e9b57
RDX: 0000000000000004 RSI: 1ffff1003b054e9d RDI: 0000000000000020
RBP: ffff8801d82a7908 R08: 1ffff1003b054e34 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffff8801d82a79e0 R14: ffff8801c5f54588 R15: ffff8801d1cb1a00
FS:  0000000001763880(0000) GS:ffff8801db400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000056422776e110 CR3: 00000001c51bc003 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  tipc_topsrv_kern_subscr+0x7e1/0x9e0 net/tipc/topsrv.c:584
  tipc_group_create+0x6be/0x940 net/tipc/group.c:193
  tipc_sk_join net/tipc/socket.c:2759 [inline]
  tipc_setsockopt+0x28a/0xcf0 net/tipc/socket.c:2874
  SYSC_setsockopt net/socket.c:1850 [inline]
  SyS_setsockopt+0x189/0x360 net/socket.c:1829
  do_syscall_64+0x282/0x940 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x26/0x9b
RIP: 0033:0x440419
RSP: 002b:00007ffcb9e1d588 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000440419
RDX: 0000000000000087 RSI: 000000000000010f RDI: 0000000000000003
RBP: 00000000006cb018 R08: 0000000000000010 R09: 0000000000000033
R10: 0000000020265000 R11: 0000000000000246 R12: 0000000000000004
R13: ffffffffffffffff R14: 0000000000000000 R15: 0000000000000000
Code: fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 f1 00 00 00 4c 8b 63 08 48 b8  
00 00 00 00 00 fc ff df 49 8d 7c 24 20 48 89 fa 48 c1 ea 03 <80> 3c 02 00  
0f 85 c3 00 00 00 4d 8b 6c 24 20 4d 8d a5 58 03 00
RIP: tipc_conn_close+0x4c/0x130 net/tipc/topsrv.c:165 RSP: ffff8801d82a78e8
---[ end trace 39a5075916eff3f7 ]---
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
    (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
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