Re: [syzbot ci] Re: netfilter: nfnetlink_cthelper: use {READ,WRITE}_ONCE for accessing helper flags

[Pablo Neira Ayuso <pablo@netfilter.org>]

Hi,

On Tue, May 19, 2026 at 11:23:57PM -0700, syzbot ci wrote:
> syzbot ci has tested the following series
> 
> [v1] netfilter: nfnetlink_cthelper: use {READ,WRITE}_ONCE for accessing helper flags
> https://lore.kernel.org/all/20260519213826.1181661-1-pablo@netfilter.org
> * [PATCH nf 1/7] netfilter: nfnetlink_cthelper: use {READ,WRITE}_ONCE for accessing helper flags
> * [PATCH nf 2/7] netfilter: conntrack: add dead flag to helpers
> * [PATCH nf 3/7] netfilter: nf_conntrack_helper: add null check in nfct_help_data() calls
> * [PATCH nf 4/7] netfilter: conntrack: add null check in nfct_help() calls
> * [PATCH nf 5/7] netfilter: conntrack: add nf_ct_iterate_destroy_net()
> * [PATCH nf 6/7] netfilter: nf_conntrack_timeout: use nf_ct_iterate_destroy() to cleanup timeout going away
> * [PATCH nf 7/7] netfilter: xt_CT: fix race with rule removal and nfnetlink_queue
> 
> and found the following issue:
> WARNING in xt_ct_tg_check

I added:

WARN_ON_ONCE(help)

instead of:

WARN_ON_ONCE(!help)

I will fix in the next spin.

> 
> Full report is available here:
> https://ci.syzbot.org/series/c356956d-b1f6-4d7e-be26-6cf68d49814e
> 
> ***
> 
> WARNING in xt_ct_tg_check
> 
> tree:      nf
> URL:       https://kernel.googlesource.com/pub/scm/linux/kernel/git/netfilter/nf.git
> base:      2beba18b0160446463bf1dbd749324846db98493
> arch:      amd64
> compiler:  Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
> config:    https://ci.syzbot.org/builds/45c49e4e-439a-4d11-bc9a-3c3a5077f679/config
> syz repro: https://ci.syzbot.org/findings/9cfb9381-576b-4a17-a156-68641410fec2/syz_repro
> 
> No such timeout policy "syz1"
> ------------[ cut here ]------------
> help
> WARNING: net/netfilter/xt_CT.c:226 at xt_ct_tg_check+0x814/0xa90 net/netfilter/xt_CT.c:226, CPU#1: syz.0.17/5870
> Modules linked in:
> CPU: 1 UID: 0 PID: 5870 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
> RIP: 0010:xt_ct_tg_check+0x814/0xa90 net/netfilter/xt_CT.c:226
> Code: c7 c7 c0 a7 e6 8c e8 eb 33 3e f7 e9 12 ff ff ff e8 01 4b dc f7 48 c7 c7 40 a8 e6 8c 4c 89 ee e8 d2 33 3e f7 e9 f9 fe ff ff 90 <0f> 0b 90 4c 89 e0 48 c1 e8 03 42 80 3c 38 00 74 08 4c 89 e7 e8 73
> RSP: 0018:ffffc900036ef6e0 EFLAGS: 00010282
> RAX: ffff88812063bd10 RBX: 1ffff920006ddee4 RCX: 0000000000000010
> RDX: ffff88812063bd00 RSI: 0000000000000002 RDI: 0000000000000002
> RBP: ffffc900036ef7b0 R08: ffffffff90316c23 R09: 1ffffffff2062d84
> R10: dffffc0000000000 R11: fffffbfff2062d85 R12: ffff88812063bd10
> R13: 00000000fffffffe R14: ffff888113ee1800 R15: dffffc0000000000
> FS:  00007fd41ea436c0(0000) GS:ffff8882a928a000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fd41da72780 CR3: 0000000175cc8000 CR4: 00000000000006f0
> Call Trace:
>  <TASK>
>  xt_checkentry_target net/netfilter/x_tables.c:1115 [inline]
>  xt_check_target+0x61a/0xca0 net/netfilter/x_tables.c:1138
>  check_target net/ipv4/netfilter/ip_tables.c:510 [inline]
>  find_check_entry net/ipv4/netfilter/ip_tables.c:552 [inline]
>  translate_table+0x1881/0x2110 net/ipv4/netfilter/ip_tables.c:716
>  do_replace net/ipv4/netfilter/ip_tables.c:1137 [inline]
>  do_ipt_set_ctl+0x9f5/0xe00 net/ipv4/netfilter/ip_tables.c:1635
>  nf_setsockopt+0x26f/0x290 net/netfilter/nf_sockopt.c:101
>  do_sock_setsockopt+0x17c/0x1b0 net/socket.c:2381
>  __sys_setsockopt net/socket.c:2406 [inline]
>  __do_sys_setsockopt net/socket.c:2412 [inline]
>  __se_sys_setsockopt net/socket.c:2409 [inline]
>  __x64_sys_setsockopt+0x13d/0x1b0 net/socket.c:2409
>  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>  do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fd41db9ce59
> 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:00007fd41ea43028 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
> RAX: ffffffffffffffda RBX: 00007fd41de15fa0 RCX: 00007fd41db9ce59
> RDX: 0000000000000040 RSI: 8001000000000000 RDI: 0000000000000003
> RBP: 00007fd41dc32d6f R08: 00000000000002a8 R09: 0000000000000000
> R10: 0000200000001500 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007fd41de16038 R14: 00007fd41de15fa0 R15: 00007ffdb7f510f8
>  </TASK>
> 
> 
> ***
> 
> If these findings have caused you to resend the series or submit a
> separate fix, please add the following tag to your commit message:
>   Tested-by: syzbot@syzkaller.appspotmail.com
> 
> ---
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