Message-ID: <692056f6.a70a0220.2ea503.004e.GAE@google.com>
Date: Fri, 21 Nov 2025 04:11:34 -0800
From: syzbot <syzbot+9475dcc0b42355ded022@...kaller.appspotmail.com>
To: davem@...emloft.net, edumazet@...gle.com, geliang@...nel.org, 
	horms@...nel.org, kuba@...nel.org, linux-kernel@...r.kernel.org, 
	martineau@...nel.org, matttbe@...nel.org, mptcp@...ts.linux.dev, 
	netdev@...r.kernel.org, pabeni@...hat.com, syzkaller-bugs@...glegroups.com
Subject: [syzbot] [mptcp?] WARNING in __mptcp_move_skbs_from_subflow (2)

Hello,

syzbot found the following issue on:

HEAD commit:    fd95357fd8c6 Merge tag 'sched_ext-for-6.18-rc6-fixes-2' of..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17220e92580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1cd7f786c0f5182f
dashboard link: https://syzkaller.appspot.com/bug?extid=9475dcc0b42355ded022
compiler:       gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: i386

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

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-fd95357f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9301ea2e80a9/vmlinux-fd95357f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/13592a9d2a74/bzImage-fd95357f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9475dcc0b42355ded022@...kaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 2 PID: 1143 at net/mptcp/protocol.c:718 __mptcp_move_skbs_from_subflow+0xeda/0x3360 net/mptcp/protocol.c:718
Modules linked in:
CPU: 2 UID: 0 PID: 1143 Comm: kworker/u32:7 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Workqueue: krdsd rds_shutdown_worker
RIP: 0010:__mptcp_move_skbs_from_subflow+0xeda/0x3360 net/mptcp/protocol.c:718
Code: 75 f6 e8 09 a8 75 f6 8b 5c 24 18 8b 6c 24 70 01 5c 24 1c 89 ee 89 df e8 74 a2 75 f6 39 dd 0f 83 d9 f3 ff ff e8 e7 a7 75 f6 90 <0f> 0b 90 48 b8 00 00 00 00 00 fc ff df 48 8b 54 24 48 48 c1 ea 03
RSP: 0018:ffffc90000537aa0 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000001508 RCX: ffffffff8b46af8c
RDX: ffff888021412480 RSI: ffffffff8b46af99 RDI: 0000000000000004
RBP: 00000000000010bc R08: 0000000000000004 R09: 0000000000001508
R10: 00000000000010bc R11: 0000000000000001 R12: ffff88806b1b00e8
R13: ffffffff9afc3e80 R14: dffffc0000000000 R15: ffff88806b1b0000
FS:  0000000000000000(0000) GS:ffff888097a0d000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000c230000 CR3: 00000000663a8000 CR4: 0000000000352ef0
Call Trace:
 <IRQ>
 move_skbs_to_msk net/mptcp/protocol.c:833 [inline]
 __mptcp_data_ready net/mptcp/protocol.c:853 [inline]
 mptcp_data_ready+0x251/0x6c0 net/mptcp/protocol.c:870
 subflow_state_change+0x4fb/0x800 net/mptcp/subflow.c:1870
 tcp_rcv_state_process+0x453b/0x6490 net/ipv4/tcp_input.c:7073
 tcp_v6_do_rcv+0x7b8/0x1dc0 net/ipv6/tcp_ipv6.c:1675
 tcp_v6_rcv+0x2ab5/0x48f0 net/ipv6/tcp_ipv6.c:1922
 ip6_protocol_deliver_rcu+0x188/0x1520 net/ipv6/ip6_input.c:438
 ip6_input_finish+0x1e4/0x4b0 net/ipv6/ip6_input.c:489
 NF_HOOK include/linux/netfilter.h:318 [inline]
 NF_HOOK include/linux/netfilter.h:312 [inline]
 ip6_input+0x105/0x2f0 net/ipv6/ip6_input.c:500
 dst_input include/net/dst.h:474 [inline]
 ip6_rcv_finish+0x1ac/0x580 net/ipv6/ip6_input.c:79
 ip_sabotage_in+0x21e/0x290 net/bridge/br_netfilter_hooks.c:990
 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
 nf_hook_slow+0xbe/0x200 net/netfilter/core.c:623
 nf_hook.constprop.0+0x424/0x750 include/linux/netfilter.h:273
 NF_HOOK include/linux/netfilter.h:316 [inline]
 ipv6_rcv+0xa4/0x650 net/ipv6/ip6_input.c:311
 __netif_receive_skb_one_core+0x12d/0x1e0 net/core/dev.c:6079
 __netif_receive_skb+0x1d/0x160 net/core/dev.c:6192
 netif_receive_skb_internal net/core/dev.c:6278 [inline]
 netif_receive_skb+0x137/0x7b0 net/core/dev.c:6337
 NF_HOOK include/linux/netfilter.h:318 [inline]
 NF_HOOK include/linux/netfilter.h:312 [inline]
 br_pass_frame_up+0x346/0x490 net/bridge/br_input.c:70
 br_handle_frame_finish+0x12fe/0x1f00 net/bridge/br_input.c:222
 br_nf_hook_thresh+0x307/0x410 net/bridge/br_netfilter_hooks.c:1167
 br_nf_pre_routing_finish_ipv6+0x76a/0xfc0 net/bridge/br_netfilter_ipv6.c:154
 NF_HOOK include/linux/netfilter.h:318 [inline]
 br_nf_pre_routing_ipv6+0x3cd/0x8c0 net/bridge/br_netfilter_ipv6.c:184
 br_nf_pre_routing+0x860/0x15b0 net/bridge/br_netfilter_hooks.c:508
 nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
 nf_hook_bridge_pre net/bridge/br_input.c:291 [inline]
 br_handle_frame+0xb28/0x14e0 net/bridge/br_input.c:442
 __netif_receive_skb_core.constprop.0+0xa25/0x4bd0 net/core/dev.c:5966
 __netif_receive_skb_one_core+0xb0/0x1e0 net/core/dev.c:6077
 __netif_receive_skb+0x1d/0x160 net/core/dev.c:6192
 process_backlog+0x439/0x15e0 net/core/dev.c:6544
 __napi_poll.constprop.0+0xba/0x550 net/core/dev.c:7594
 napi_poll net/core/dev.c:7657 [inline]
 net_rx_action+0x97f/0xef0 net/core/dev.c:7784
 handle_softirqs+0x219/0x8e0 kernel/softirq.c:622
 do_softirq kernel/softirq.c:523 [inline]
 do_softirq+0xb2/0xf0 kernel/softirq.c:510
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0x100/0x120 kernel/softirq.c:450
 local_bh_enable include/linux/bottom_half.h:33 [inline]
 rcu_read_unlock_bh include/linux/rcupdate.h:936 [inline]
 __dev_queue_xmit+0xb06/0x4490 net/core/dev.c:4790
 dev_queue_xmit include/linux/netdevice.h:3365 [inline]
 neigh_hh_output include/net/neighbour.h:531 [inline]
 neigh_output include/net/neighbour.h:545 [inline]
 ip6_finish_output2+0x1184/0x1cf0 net/ipv6/ip6_output.c:136
 __ip6_finish_output+0x3cd/0x1010 net/ipv6/ip6_output.c:209
 ip6_finish_output net/ipv6/ip6_output.c:220 [inline]
 NF_HOOK_COND include/linux/netfilter.h:307 [inline]
 ip6_output+0x253/0x710 net/ipv6/ip6_output.c:247
 dst_output include/net/dst.h:464 [inline]
 NF_HOOK include/linux/netfilter.h:318 [inline]
 NF_HOOK include/linux/netfilter.h:312 [inline]
 ip6_xmit+0x1512/0x23f0 net/ipv6/ip6_output.c:371
 inet6_csk_xmit+0x444/0x7f0 net/ipv6/inet6_connection_sock.c:120
 __tcp_transmit_skb+0x1d67/0x44d0 net/ipv4/tcp_output.c:1628
 tcp_transmit_skb net/ipv4/tcp_output.c:1646 [inline]
 tcp_write_xmit+0x12a9/0x86e0 net/ipv4/tcp_output.c:2999
 __tcp_push_pending_frames+0xaf/0x390 net/ipv4/tcp_output.c:3182
 tcp_send_fin+0x121/0x1050 net/ipv4/tcp_output.c:3800
 __tcp_close+0xa46/0x1120 net/ipv4/tcp.c:3207
 tcp_close+0x28/0x120 net/ipv4/tcp.c:3298
 inet_release+0xed/0x200 net/ipv4/af_inet.c:437
 inet6_release+0x4f/0x70 net/ipv6/af_inet6.c:487
 __sock_release net/socket.c:662 [inline]
 sock_release+0x91/0x1d0 net/socket.c:690
 rds_tcp_conn_path_shutdown+0x1f9/0x410 net/rds/tcp_connect.c:220
 rds_conn_shutdown+0x28b/0xaa0 net/rds/connection.c:399
 process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3263
 process_scheduled_works kernel/workqueue.c:3346 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3427
 kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x675/0x7d0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>


---
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