Re: [syzbot] [net?] WARNING in tcf_ct_flow_table_process_conn

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

syzbot has found a reproducer for the following issue on:

HEAD commit:    238650ef6c7c Merge tag 'powerpc-7.3-4' of git://git.kernel..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=15663bf9580000
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
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=160653f9580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14cbebf9580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/78c78695c277/disk-238650ef.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ed193a418b0f/vmlinux-238650ef.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f7a21c8aa010/bzImage-238650ef.xz

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

RDX: 000000000000001c RSI: 0000200000000500 RDI: 0000000000000003
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000200000000500
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
------------[ cut here ]------------
1
WARNING: net/sched/act_ct.c:437 at tcf_ct_flow_table_add net/sched/act_ct.c:437 [inline], CPU#0: syz-executor278/6366
WARNING: net/sched/act_ct.c:437 at tcf_ct_flow_table_process_conn+0x449/0x7c0 net/sched/act_ct.c:513, CPU#0: syz-executor278/6366
Modules linked in:
CPU: 0 UID: 0 PID: 6366 Comm: syz-executor278 Not tainted syzkaller #0 PREEMPT(full) 
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 2f 67 e9 f7 85 ed 0f 84 7c 01 00 00 e8 e2 62 e9 f7 e9 e0 01 00 00 e8 d8 62 e9 f7 90 <0f> 0b 90 e9 b2 01 00 00 e8 ca 62 e9 f7 4d 89 f7 40 84 ed 74 27 e8
RSP: 0018:ffffc900042d6ef8 EFLAGS: 00010293
RAX: ffffffff89de6f88 RBX: ffff888070202000 RCX: ffff888028c90000
RDX: 0000000000000000 RSI: ffffffff8c6da060 RDI: ffffffff8c6da020
RBP: 0000000000000000 R08: 00000000ffffffff R09: 1ffffffff1dd5cfe
R10: dffffc0000000000 R11: fffffbfff1dd5cff R12: dffffc0000000000
R13: 1ffff1100e04041e R14: ffff8880702020c0 R15: 0000000000000001
FS:  000055556fc09400(0000) GS:ffff888124cd1000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffe25dff4c8 CR3: 0000000079ba6000 CR4: 00000000003526f0
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]
 netif_receive_skb_internal net/core/dev.c:6463 [inline]
 netif_receive_skb+0x1fe/0xbf0 net/core/dev.c:6522
 tun_rx_batched+0x1de/0x790 drivers/net/tun.c:1571
 tun_get_user+0x2be0/0x44d0 drivers/net/tun.c:2045
 tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:2091
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x612/0xba0 fs/read_write.c:687
 ksys_write+0x150/0x270 fs/read_write.c:739
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f6c0bc30879
Code: c0 79 93 eb d5 48 8d 7c 1d 00 eb 99 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 d8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffff5b95668 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007ffff5b95690 RCX: 00007f6c0bc30879
RDX: 000000000000001c RSI: 0000200000000500 RDI: 0000000000000003
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000200000000500
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>


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