[syzbot] linux-next test error: WARNING in __nf_unregister_net_hook

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    74f961f4 Add linux-next specific files for 20210430
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=156e6f15d00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=acf3aa1c9f3e62f8
dashboard link: https://syzkaller.appspot.com/bug?extid=dcccba8a1e41a38cb9df

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+dcccba8a1e41a38cb9df@xxxxxxxxxxxxxxxxxxxxxxxxx

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hook not found, pf 3 num 0
WARNING: CPU: 0 PID: 224 at net/netfilter/core.c:480 __nf_unregister_net_hook+0x1eb/0x610 net/netfilter/core.c:480
Modules linked in:
CPU: 0 PID: 224 Comm: kworker/u4:5 Not tainted 5.12.0-next-20210430-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: netns cleanup_net
RIP: 0010:__nf_unregister_net_hook+0x1eb/0x610 net/netfilter/core.c:480
Code: 0f b6 14 02 48 89 c8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 11 04 00 00 8b 53 1c 89 ee 48 c7 c7 c0 4d 6e 8a e8 e8 5b 8a 01 <0f> 0b e9 e5 00 00 00 e8 99 dd 2c fa 44 8b 3c 24 4c 89 f8 48 c1 e0
RSP: 0018:ffffc900015bfbc0 EFLAGS: 00010286
RAX: 0000000000000000 RBX: ffff8880243de500 RCX: 0000000000000000
RDX: ffff888012df3900 RSI: ffffffff815cc9f5 RDI: fffff520002b7f6a
RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff815c685e R11: 0000000000000000 R12: ffff88802e9c0f20
R13: 0000000000000000 R14: ffff888019fb2180 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc78cbbe010 CR3: 0000000012d10000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 nf_unregister_net_hook net/netfilter/core.c:502 [inline]
 nf_unregister_net_hooks+0x117/0x160 net/netfilter/core.c:576
 arpt_unregister_table_pre_exit+0x67/0x80 net/ipv4/netfilter/arp_tables.c:1565
 ops_pre_exit_list net/core/net_namespace.c:165 [inline]
 cleanup_net+0x451/0xb10 net/core/net_namespace.c:583
 process_one_work+0x98d/0x1600 kernel/workqueue.c:2275
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2421
 kthread+0x3b1/0x4a0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294


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