Subject: WARNING: proc registration bug in clusterip_tg_check

From: syzbot <[email-masked]>
Date: Tue, 06 Feb 2018 06:27:01 -0800

Hello,

syzbot hit the following crash on net-next commit
617aebe6a97efa539cc4b8a52adccd89596e6be0 (Sun Feb 4 00:25:42 2018 +0000)
Merge tag 'usercopy-v4.16-rc1' of  
git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

So far this crash happened 5 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.

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Reported-by: [email-masked]
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x_tables: ip_tables: osf match: only valid for protocol 6
x_tables: ip_tables: osf match: only valid for protocol 6
x_tables: ip_tables: osf match: only valid for protocol 6
------------[ cut here ]------------
proc_dir_entry 'ipt_CLUSTERIP/172.20.0.170' already registered
WARNING: CPU: 1 PID: 4152 at fs/proc/generic.c:330  
proc_register+0x2a4/0x370 fs/proc/generic.c:329
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 4152 Comm: syzkaller851476 Not tainted 4.15.0+ #221
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:1097
RIP: 0010:proc_register+0x2a4/0x370 fs/proc/generic.c:329
RSP: 0018:ffff8801cbd6ee20 EFLAGS: 00010286
RAX: dffffc0000000008 RBX: ffff8801d2181038 RCX: ffffffff815a57ae
RDX: 0000000000000000 RSI: 1ffff100397add74 RDI: 1ffff100397add49
RBP: ffff8801cbd6ee70 R08: 1ffff100397add0b R09: 0000000000000000
R10: ffff8801cbd6ecd8 R11: 0000000000000000 R12: ffff8801b2bb1cc0
R13: dffffc0000000000 R14: ffff8801b0d8dbc8 R15: ffff8801b2bb1d81
  proc_create_data+0xf8/0x180 fs/proc/generic.c:494
  clusterip_config_init net/ipv4/netfilter/ipt_CLUSTERIP.c:250 [inline]
  clusterip_tg_check+0xf9c/0x16d0 net/ipv4/netfilter/ipt_CLUSTERIP.c:488
  xt_check_target+0x22c/0x7d0 net/netfilter/x_tables.c:850
  check_target net/ipv4/netfilter/ip_tables.c:513 [inline]
  find_check_entry.isra.8+0x8c8/0xcb0 net/ipv4/netfilter/ip_tables.c:554
  translate_table+0xed1/0x1610 net/ipv4/netfilter/ip_tables.c:725
  do_replace net/ipv4/netfilter/ip_tables.c:1141 [inline]
  do_ipt_set_ctl+0x370/0x5f0 net/ipv4/netfilter/ip_tables.c:1675
  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:1259
  sctp_setsockopt+0x2b6/0x61d0 net/sctp/socket.c:4104
  sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2975
  SYSC_setsockopt net/socket.c:1849 [inline]
  SyS_setsockopt+0x189/0x360 net/socket.c:1828
  entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x446839
RSP: 002b:00007f0309d0fdb8 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 00000000006dbc24 RCX: 0000000000446839
RDX: 0000000000000040 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00000000006dbc20 R08: 0000000000000348 R09: 0000000000000000
R10: 0000000020013c90 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffc7d53f79f R14: 00007f0309d109c0 R15: 0000000000000003
Dumping ftrace buffer:
    (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..

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