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 6 times on net-next, upstream.
C reproducer is attached.
syzkaller reproducer is attached.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+fe0b19af568972814355@syzkaller.appspotmail.com
It will help syzbot understand when the bug is fixed. See footer for  
details.
If you forward the report, please keep this part and the footer.

IPVS: ftp: loaded support on port[0] = 21
BUG: unable to handle kernel paging request at ffffc900017c752d
IP: ebt_among_mt_check+0x170/0x350 net/bridge/netfilter/ebt_among.c:187
PGD 1db12d067 P4D 1db12d067 PUD 1db12e067 PMD 1c3322067 PTE 0
Oops: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
    (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 4122 Comm: syzkaller721371 Not tainted 4.16.0-rc1+ #231
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:ebt_among_mt_check+0x170/0x350  
net/bridge/netfilter/ebt_among.c:187
RSP: 0018:ffff8801cd37f210 EFLAGS: 00010246
RAX: 0000000000000008 RBX: ffffc900017bf128 RCX: ffffffff84f12f1e
RDX: 0000000000000000 RSI: 0000000000000870 RDI: ffffc900017c752d
RBP: ffff8801cd37f240 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff8818c280 R11: 0000000000000000 R12: ffffc900017c7129
R13: ffff8801cd37f548 R14: ffffc900017bf131 R15: 0000000030000414
FS:  000000000170d940(0000) GS:ffff8801db500000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffc900017c752d CR3: 00000001ba8a3004 CR4: 00000000001606e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  xt_check_match+0x231/0x7d0 net/netfilter/x_tables.c:470
  ebt_check_match net/bridge/netfilter/ebtables.c:374 [inline]
  ebt_check_entry+0xbc3/0x1e00 net/bridge/netfilter/ebtables.c:704
  translate_table+0xcf5/0x2290 net/bridge/netfilter/ebtables.c:945
  do_replace_finish+0x79a/0x2620 net/bridge/netfilter/ebtables.c:1002
  do_replace+0x333/0x4b0 net/bridge/netfilter/ebtables.c:1141
  do_ebt_set_ctl+0xd4/0x110 net/bridge/netfilter/ebtables.c:1518
  nf_sockopt net/netfilter/nf_sockopt.c:106 [inline]
  nf_setsockopt+0x67/0xc0 net/netfilter/nf_sockopt.c:115
  ip_setsockopt+0x97/0xa0 net/ipv4/ip_sockglue.c:1261
  tcp_setsockopt+0x82/0xd0 net/ipv4/tcp.c:2905
  sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2979
  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: 0033:0x44cee9
RSP: 002b:00007ffcc80c4578 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000044cee9
RDX: 0000000000000080 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 000000000170e940 R08: 0000000000000d80 R09: 000000000170e940
R10: 0000000020fb1000 R11: 0000000000000246 R12: 585858582e72656c
R13: 6c616b7a79732f2e R14: 0000000000000000 R15: 0000000000000000
Code: 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 0f b6 14 02 48  
89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 c9 01 00 00 <41> 8b 84 24  
04 04 00 00 8d 04 40 45 8d bc 87 08 04 00 00 4d 63
RIP: ebt_among_mt_check+0x170/0x350 net/bridge/netfilter/ebt_among.c:187  
RSP: ffff8801cd37f210
CR2: ffffc900017c752d
---[ end trace 39ec805adb913149 ]---


---
This bug is generated by a dumb bot. It may contain errors.
See https://goo.gl/tpsmEJ for details.
Direct all questions to syzkaller@googlegroups.com.

syzbot will keep track of this bug report.
If you forgot to add the Reported-by tag, once the fix for this bug is  
merged
into any tree, please reply to this email with:
#syz fix: exact-commit-title
If you want to test a patch for this bug, please reply with:
#syz test: git://repo/address.git branch
and provide the patch inline or as an attachment.
To mark this as a duplicate of another syzbot report, please reply with:
#syz dup: exact-subject-of-another-report
If it's a one-off invalid bug report, please reply with:
#syz invalid
Note: if the crash happens again, it will cause creation of a new bug  
report.
Note: all commands must start from beginning of the line in the email body.