[v5.15] kernel BUG in __nf_conntrack_confirm (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: b9d57c40a767 Linux 5.15.203
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=113212ce580000
kernel config: https://syzkaller.appspot.com/x/.config?x=353ae28c40b35af5
dashboard link: https://syzkaller.appspot.com/bug?extid=8632983b62aa286cd88f
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/34313629ba4f/disk-b9d57c40.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/402f526e5a98/vmlinux-b9d57c40.xz
kernel image: https://storage.googleapis.com/syzbot-assets/45f7694e9617/bzImage-b9d57c40.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+863298...@syzkaller.appspotmail.com

------------[ cut here ]------------
kernel BUG at net/netfilter/nf_conntrack_core.c:570!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 3880 Comm: syz.9.6440 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:nf_ct_del_from_dying_or_unconfirmed_list net/netfilter/nf_conntrack_core.c:570 [inline]
RIP: 0010:__nf_conntrack_confirm+0x109d/0x10a0 net/netfilter/nf_conntrack_core.c:1207
Code: fc ff ff e8 e5 a2 54 f9 48 c7 c7 00 3b 85 8d 48 c7 c6 60 b3 24 8b 48 8b 54 24 08 e8 fd b8 db fb e9 fa f1 ff ff e8 c3 a2 54 f9 <0f> 0b 90 55 41 57 41 56 41 55 41 54 53 48 89 fb 48 bd 00 00 00 00
RSP: 0018:ffffc90000dd0820 EFLAGS: 00010246
RAX: ffffffff882491cd RBX: ffffe8ffffc260b0 RCX: ffff88802c6c8000
RDX: 0000000000000100 RSI: 0000000000000004 RDI: ffffc90000dd07a0
RBP: ffff88807a59cc00 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff520001ba0f4 R12: 0000000000034b73
R13: 0000000000000000 R14: ffff88807a59cc58 R15: 0000000000000000
FS: 00007ff813da16c0(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000001240 CR3: 000000005eee7000 CR4: 00000000003506e0
Call Trace:
<IRQ>
nf_conntrack_confirm include/net/netfilter/nf_conntrack_core.h:62 [inline]
nf_confirm+0x381/0x4b0 net/netfilter/nf_conntrack_proto.c:154
nf_hook_entry_hookfn include/linux/netfilter.h:142 [inline]
nf_hook_slow+0xb9/0x200 net/netfilter/core.c:584
nf_hook include/linux/netfilter.h:257 [inline]
NF_HOOK+0x1f2/0x390 include/linux/netfilter.h:300
NF_HOOK+0x303/0x390 include/linux/netfilter.h:302
__netif_receive_skb_one_core net/core/dev.c:5551 [inline]
__netif_receive_skb+0xcc/0x290 net/core/dev.c:5665
process_backlog+0x370/0x790 net/core/dev.c:6542
__napi_poll+0xc0/0x430 net/core/dev.c:7101
napi_poll net/core/dev.c:7168 [inline]
net_rx_action+0x4d4/0xa10 net/core/dev.c:7258
handle_softirqs+0x339/0x830 kernel/softirq.c:576
do_softirq+0x142/0x210 kernel/softirq.c:477
</IRQ>
<TASK>
__local_bh_enable_ip+0x180/0x1c0 kernel/softirq.c:401
rcu_read_unlock_bh include/linux/rcupdate.h:810 [inline]
ip_finish_output2+0xd50/0x10a0 net/ipv4/ip_output.c:229
NF_HOOK_COND include/linux/netfilter.h:291 [inline]
ip_output+0x2c0/0x3e0 net/ipv4/ip_output.c:434
dst_output include/net/dst.h:452 [inline]
ip_local_out net/ipv4/ip_output.c:126 [inline]
__ip_queue_xmit+0x11c1/0x1c00 net/ipv4/ip_output.c:538
__tcp_transmit_skb+0x1d11/0x3200 net/ipv4/tcp_output.c:1404
tcp_rcv_established+0x12dc/0x1ce0 net/ipv4/tcp_input.c:6033
tcp_v4_do_rcv+0x44b/0x9b0 net/ipv4/tcp_ipv4.c:1731
sk_backlog_rcv include/net/sock.h:1080 [inline]
__release_sock+0x1e1/0x450 net/core/sock.c:2731
release_sock+0x5b/0x1b0 net/core/sock.c:3274
tcp_sendmsg+0x35/0x40 net/ipv4/tcp.c:1461
sock_sendmsg_nosec net/socket.c:706 [inline]
__sock_sendmsg net/socket.c:718 [inline]
____sys_sendmsg+0x5b7/0x8f0 net/socket.c:2445
___sys_sendmsg+0x236/0x2e0 net/socket.c:2499
__sys_sendmmsg+0x2ba/0x500 net/socket.c:2585
__do_sys_sendmmsg net/socket.c:2614 [inline]
__se_sys_sendmmsg net/socket.c:2611 [inline]
__x64_sys_sendmmsg+0x9c/0xb0 net/socket.c:2611
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7ff815b47dd9
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:00007ff813da1028 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007ff815dc0fa0 RCX: 00007ff815b47dd9
RDX: 0000000000000001 RSI: 0000200000001240 RDI: 0000000000000003
RBP: 00007ff815bddd69 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff815dc1038 R14: 00007ff815dc0fa0 R15: 00007ffeb798ba88
</TASK>
Modules linked in:
---[ end trace 522820537b2827e3 ]---
RIP: 0010:nf_ct_del_from_dying_or_unconfirmed_list net/netfilter/nf_conntrack_core.c:570 [inline]
RIP: 0010:__nf_conntrack_confirm+0x109d/0x10a0 net/netfilter/nf_conntrack_core.c:1207
Code: fc ff ff e8 e5 a2 54 f9 48 c7 c7 00 3b 85 8d 48 c7 c6 60 b3 24 8b 48 8b 54 24 08 e8 fd b8 db fb e9 fa f1 ff ff e8 c3 a2 54 f9 <0f> 0b 90 55 41 57 41 56 41 55 41 54 53 48 89 fb 48 bd 00 00 00 00
RSP: 0018:ffffc90000dd0820 EFLAGS: 00010246
RAX: ffffffff882491cd RBX: ffffe8ffffc260b0 RCX: ffff88802c6c8000
RDX: 0000000000000100 RSI: 0000000000000004 RDI: ffffc90000dd07a0
RBP: ffff88807a59cc00 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff520001ba0f4 R12: 0000000000034b73
R13: 0000000000000000 R14: ffff88807a59cc58 R15: 0000000000000000
FS: 00007ff813da16c0(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000001240 CR3: 000000005eee7000 CR4: 00000000003506e0


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