general protection fault in get_info

Hello,

syzkaller hit the following crash on  
8418f88764046d0e8ca6a3c04a69a0e57189aa1e
git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.
C reproducer is attached
syzkaller reproducer is attached. See https://goo.gl/kgGztJ
for information about syzkaller reproducers


IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+980925dbfbc7f93bc2ef@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.

audit: type=1400 audit(1515655003.740:7): avc:  denied  { map } for   
pid=3507 comm="syzkaller630068" path="/root/syzkaller630068803" dev="sda1"  
ino=16481 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023  
tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
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: 3507 Comm: syzkaller630068 Not tainted  
4.15.0-rc7-next-20180111+ #94
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:get_info+0x17d/0x690 net/ipv6/netfilter/ip6_tables.c:992
RSP: 0018:ffff8801bfad78e0 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffffffff86e9a840 RCX: ffffffff84a8c538
RDX: 0000000000000023 RSI: 0000000000000000 RDI: 0000000000000118
RBP: ffff8801bfad7a70 R08: 1ffff10037f5ae53 R09: 0000000000000000
R10: ffffffff87f4aee0 R11: 0000000000000000 R12: ffff8801bfad7a48
R13: 1ffff10037f5af21 R14: 0000000000000100 R15: ffff8801bfad7c78
FS:  0000000001692880(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffd94855d80 CR3: 00000001bf4da002 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  do_ipt_get_ctl+0x159/0xac0 net/ipv4/netfilter/ip_tables.c:1699
  nf_sockopt net/netfilter/nf_sockopt.c:104 [inline]
  nf_getsockopt+0x6a/0xc0 net/netfilter/nf_sockopt.c:122
  ip_getsockopt+0x15c/0x220 net/ipv4/ip_sockglue.c:1573
  udp_getsockopt+0x45/0x80 net/ipv4/udp.c:2460
  ipv6_getsockopt+0xf3/0x2e0 net/ipv6/ipv6_sockglue.c:1363
  udpv6_getsockopt+0x45/0x80 net/ipv6/udp.c:1441
  sock_common_getsockopt+0x95/0xd0 net/core/sock.c:2937
  SYSC_getsockopt net/socket.c:1852 [inline]
  SyS_getsockopt+0x178/0x340 net/socket.c:1834
  entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x43fc89
RSP: 002b:00007ffe136cbf18 EFLAGS: 00000203 ORIG_RAX: 0000000000000037
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 000000000043fc89
RDX: 0000000000000040 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 0000000020001ffc R09: 0000000000000000
R10: 0000000020b3ffac R11: 0000000000000203 R12: 00000000004015f0
R13: 0000000000401680 R14: 0000000000000000 R15: 0000000000000000
Code: c1 ff 48 3d 00 f0 ff ff 49 89 c6 0f 87 d4 03 00 00 e8 58 db c7 fc 49  
8d 7e 18 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00  
0f 85 e9 04 00 00 49 8b 4e 18 49 8d 5c 24 80 48 89
RIP: get_info+0x17d/0x690 net/ipv6/netfilter/ip6_tables.c:992 RSP:  
ffff8801bfad78e0
---[ end trace 8fdfc3af33127a7a ]---
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
    (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
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.