Re: [syzbot] [netfilter?] WARNING in __nf_unregister_net_hook (9)

[syzbot <syzbot+78ac1e46d2966eb70fda@syzkaller.appspotmail.com>]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING in __nf_unregister_net_hook

------------[ cut here ]------------
hook not found, pf 5 num 0
WARNING: net/netfilter/core.c:514 at __nf_unregister_net_hook+0x2c5/0x6f0 net/netfilter/core.c:514, CPU#1: syz.1.1035/9919
Modules linked in:
CPU: 1 UID: 0 PID: 9919 Comm: syz.1.1035 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:__nf_unregister_net_hook+0x2dc/0x6f0 net/netfilter/core.c:514
Code: 24 30 48 8b 5c 24 08 44 8b 6c 24 04 48 8d 3d fb 0b 5b 06 48 8b 44 24 10 0f b6 04 28 84 c0 0f 85 f1 02 00 00 41 8b 17 44 89 ee <67> 48 0f b9 3a e9 db 01 00 00 e8 55 38 e7 01 89 c3 31 ff 89 c6 e8
RSP: 0018:ffffc9000556eb30 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff888032313d80 RCX: ffff888030ae9e40
RDX: 0000000000000000 RSI: 0000000000000005 RDI: ffffffff9020ab80
RBP: dffffc0000000000 R08: ffffffff901188b7 R09: 1ffffffff2023116
R10: dffffc0000000000 R11: fffffbfff2023117 R12: ffff88807ec62640
R13: 0000000000000005 R14: ffff88802a210490 R15: ffff88807dfd2cbc
FS:  00007fcd31fca6c0(0000) GS:ffff888125567000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2dc0fe8600 CR3: 000000007e876000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 nft_unregister_flowtable_ops net/netfilter/nf_tables_api.c:8834 [inline]
 nft_flowtable_event net/netfilter/nf_tables_api.c:9613 [inline]
 __nf_tables_flowtable_event+0x5bf/0x8c0 net/netfilter/nf_tables_api.c:9658
 nf_tables_flowtable_event+0x103/0x160 net/netfilter/nf_tables_api.c:9689
 notifier_call_chain+0x1be/0x400 kernel/notifier.c:85
 call_netdevice_notifiers_extack net/core/dev.c:2287 [inline]
 call_netdevice_notifiers net/core/dev.c:2301 [inline]
 unregister_netdevice_many_notify+0x186a/0x2370 net/core/dev.c:12412
 rtnl_newlink_create+0x84b/0xb70 net/core/rtnetlink.c:3868
 __rtnl_newlink net/core/rtnetlink.c:3957 [inline]
 rtnl_newlink+0x1666/0x1be0 net/core/rtnetlink.c:4072
 rtnetlink_rcv_msg+0x7d5/0xbe0 net/core/rtnetlink.c:6958
 netlink_rcv_skb+0x232/0x4b0 net/netlink/af_netlink.c:2550
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x80f/0x9b0 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0xa68/0xad0 net/socket.c:2592
 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2646
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2683 [inline]
 __se_sys_sendmsg net/socket.c:2681 [inline]
 __x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2681
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fcd3119aeb9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fcd31fca028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fcd31415fa0 RCX: 00007fcd3119aeb9
RDX: 0000000000000000 RSI: 0000200000000200 RDI: 0000000000000003
RBP: 00007fcd31208c1f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fcd31416038 R14: 00007fcd31415fa0 R15: 00007ffc25796e58
 </TASK>
----------------
Code disassembly (best guess):
   0:	24 30                	and    $0x30,%al
   2:	48 8b 5c 24 08       	mov    0x8(%rsp),%rbx
   7:	44 8b 6c 24 04       	mov    0x4(%rsp),%r13d
   c:	48 8d 3d fb 0b 5b 06 	lea    0x65b0bfb(%rip),%rdi        # 0x65b0c0e
  13:	48 8b 44 24 10       	mov    0x10(%rsp),%rax
  18:	0f b6 04 28          	movzbl (%rax,%rbp,1),%eax
  1c:	84 c0                	test   %al,%al
  1e:	0f 85 f1 02 00 00    	jne    0x315
  24:	41 8b 17             	mov    (%r15),%edx
  27:	44 89 ee             	mov    %r13d,%esi
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	e9 db 01 00 00       	jmp    0x20f
  34:	e8 55 38 e7 01       	call   0x1e7388e
  39:	89 c3                	mov    %eax,%ebx
  3b:	31 ff                	xor    %edi,%edi
  3d:	89 c6                	mov    %eax,%esi
  3f:	e8                   	.byte 0xe8


Tested on:

commit:         fd6dad4e netmem: remove the pp fields from net_iov
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1449a8d6580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=75b1f89e973ee407
dashboard link: https://syzkaller.appspot.com/bug?extid=78ac1e46d2966eb70fda
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

Note: no patches were applied.