WARNING: proc registration bug in clusterip_tg_check

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 54b4fa6d Linux 4.19.113
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=124650ade00000
kernel config: https://syzkaller.appspot.com/x/.config?x=7b1a0bc5526ebc49
dashboard link: https://syzkaller.appspot.com/bug?extid=53f6ab47388a185f66cb
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+53f6ab...@syzkaller.appspotmail.com

------------[ cut here ]------------
proc_dir_entry 'ipt_CLUSTERIP/127.0.0.1' already registered
WARNING: CPU: 1 PID: 28681 at fs/proc/generic.c:359 proc_register+0x3d4/0x540 fs/proc/generic.c:359
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 28681 Comm: syz-executor.5 Not tainted 4.19.113-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x188/0x20d lib/dump_stack.c:118
panic+0x26a/0x50e kernel/panic.c:186
__warn.cold+0x20/0x46 kernel/panic.c:541
report_bug+0x262/0x2a0 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:178 [inline]
fixup_bug arch/x86/kernel/traps.c:173 [inline]
do_error_trap+0x1d7/0x310 arch/x86/kernel/traps.c:296
invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:1037
RIP: 0010:proc_register+0x3d4/0x540 fs/proc/generic.c:359
Code: ff df 48 89 f9 48 c1 e9 03 80 3c 01 00 0f 85 61 01 00 00 48 8b 04 24 48 c7 c7 60 e8 76 87 48 8b b0 d0 00 00 00 e8 f7 40 76 ff <0f> 0b 48 c7 c7 80 60 c7 88 e8 ee 4a 59 05 48 8b 4c 24 28 48 b8 00
RSP: 0018:ffff88805288f6a8 EFLAGS: 00010286
RAX: 0000000000000000 RBX: ffff8880a779a670 RCX: 0000000000000000
RDX: 000000000000fe5c RSI: ffffffff8152d3a1 RDI: ffffed100a511ec7
RBP: ffff888054a51080 R08: ffff888061a26480 R09: ffffed1015ce3ee3
R10: ffffed1015ce3ee2 R11: ffff8880ae71f717 R12: 0000000000000000
R13: dffffc0000000000 R14: ffff88809ab0b8b8 R15: 0000000000000009
proc_create_data+0xc4/0x120 fs/proc/generic.c:548
clusterip_config_init net/ipv4/netfilter/ipt_CLUSTERIP.c:285 [inline]
clusterip_tg_check+0x1101/0x1627 net/ipv4/netfilter/ipt_CLUSTERIP.c:506
xt_check_target+0x267/0x650 net/netfilter/x_tables.c:1024
check_target net/ipv4/netfilter/ip_tables.c:514 [inline]
find_check_entry.isra.0+0x6f0/0x8d0 net/ipv4/netfilter/ip_tables.c:556
translate_table+0xbcc/0x1610 net/ipv6/netfilter/ip6_tables.c:736
do_replace net/ipv4/netfilter/ip_tables.c:1139 [inline]
do_ipt_set_ctl+0x29d/0x41f net/ipv4/netfilter/ip_tables.c:1675
nf_sockopt net/netfilter/nf_sockopt.c:106 [inline]
nf_setsockopt+0x6f/0xc0 net/netfilter/nf_sockopt.c:115
ip_setsockopt net/ipv4/ip_sockglue.c:1258 [inline]
ip_setsockopt+0xd8/0xf0 net/ipv4/ip_sockglue.c:1238
udp_setsockopt+0x5d/0xa0 net/ipv4/udp.c:2549
__sys_setsockopt+0x14d/0x240 net/socket.c:1901
__do_sys_setsockopt net/socket.c:1912 [inline]
__se_sys_setsockopt net/socket.c:1909 [inline]
__x64_sys_setsockopt+0xba/0x150 net/socket.c:1909
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c849
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ff12d820c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 00007ff12d8216d4 RCX: 000000000045c849
RDX: 0000000000000040 RSI: 0004000000000000 RDI: 0000000000000003
RBP: 000000000076bfa0 R08: 0000000000000260 R09: 0000000000000000
R10: 0000000020000240 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000a37 R14: 00000000004ccdf6 R15: 000000000076bfac
Kernel Offset: disabled
Rebooting in 86400 seconds..


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.