[syzbot] [net?] WARNING in tcf_ct_flow_table_process_conn

[syzbot <syzbot+6cc37aba98dac721c415@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    5225b8eec4c9 mailmap: update entry for Jens Axboe
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=165795f9580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5e4e3a0e188a497e
dashboard link: https://syzkaller.appspot.com/bug?extid=6cc37aba98dac721c415
compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/8ec9ac0f583a/disk-5225b8ee.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ba864b419b40/vmlinux-5225b8ee.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ddacae1aa6db/bzImage-5225b8ee.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6cc37aba98dac721c415@syzkaller.appspotmail.com

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1
WARNING: net/sched/act_ct.c:437 at tcf_ct_flow_table_add net/sched/act_ct.c:437 [inline], CPU#0: ksoftirqd/0/15
WARNING: net/sched/act_ct.c:437 at tcf_ct_flow_table_process_conn+0x449/0x7c0 net/sched/act_ct.c:513, CPU#0: ksoftirqd/0/15
Modules linked in:
CPU: 0 UID: 0 PID: 15 Comm: ksoftirqd/0 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:tcf_ct_flow_table_add net/sched/act_ct.c:437 [inline]
RIP: 0010:tcf_ct_flow_table_process_conn+0x449/0x7c0 net/sched/act_ct.c:513
Code: 85 81 02 00 00 41 0f b7 2f 31 ff 89 ee e8 6f b1 e9 f7 85 ed 0f 84 7c 01 00 00 e8 22 ad e9 f7 e9 e0 01 00 00 e8 18 ad e9 f7 90 <0f> 0b 90 e9 b2 01 00 00 e8 0a ad e9 f7 4d 89 f7 40 84 ed 74 27 e8
RSP: 0018:ffffc900001471d8 EFLAGS: 00010246
RAX: ffffffff89de1d98 RBX: ffff8880774aa000 RCX: ffff88801e299f40
RDX: 8000000000000100 RSI: 0000000000000100 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000100 R09: 1ffff1100ee95418
R10: dffffc0000000000 R11: ffffed100ee95419 R12: dffffc0000000000
R13: 1ffff1100ee9541e R14: ffff8880774aa0c0 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff888124cd2000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f40fd23ffd0 CR3: 0000000028424000 CR4: 00000000003526f0
DR0: ffffffffffffffff DR1: 00000000000001f8 DR2: 0000000000000083
DR3: ffffffffefffff15 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 tcf_ct_act+0x2a75/0x4050 net/sched/act_ct.c:1123
 tc_act include/net/tc_wrapper.h:131 [inline]
 tcf_action_exec+0x185/0x8d0 net/sched/act_api.c:1162
 tcf_exts_exec include/net/pkt_cls.h:361 [inline]
 basic_classify+0x1b2/0x2d0 net/sched/cls_basic.c:54
 tc_classify include/net/tc_wrapper.h:198 [inline]
 __tcf_classify net/sched/cls_api.c:1779 [inline]
 tcf_classify+0x43d/0x1160 net/sched/cls_api.c:1875
 tc_run+0x42d/0x750 net/core/dev.c:4463
 sch_handle_ingress net/core/dev.c:4538 [inline]
 __netif_receive_skb_core+0x1443/0x30c0 net/core/dev.c:6115
 __netif_receive_skb_one_core net/core/dev.c:6262 [inline]
 __netif_receive_skb net/core/dev.c:6377 [inline]
 process_backlog+0x727/0x18b0 net/core/dev.c:6728
 __napi_poll+0xaa/0x330 net/core/dev.c:7787
 napi_poll net/core/dev.c:7850 [inline]
 net_rx_action+0x61d/0xf50 net/core/dev.c:8007
 handle_softirqs+0x226/0x860 kernel/softirq.c:645
 run_ksoftirqd+0x36/0x60 kernel/softirq.c:1099
 smpboot_thread_fn+0x565/0xa70 kernel/smpboot.c:160
 kthread+0x38b/0x480 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>


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