[v6.6] WARNING in subflow_data_ready

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 5fa4793a2d2d Linux 6.6.119
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=17143a1a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=691a6769a86ac817
dashboard link: https://syzkaller.appspot.com/bug?extid=32c1241cc455e5d3fc88
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/63699875f1dd/disk-5fa4793a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8506652fcb6f/vmlinux-5fa4793a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1b30ceed1710/bzImage-5fa4793a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+32c124...@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 0 PID: 2950 at net/mptcp/subflow.c:1472 subflow_data_ready+0x412/0x660 net/mptcp/subflow.c:1471
Modules linked in:
CPU: 0 PID: 2950 Comm: kworker/u4:9 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: krdsd rds_send_worker
RIP: 0010:subflow_data_ready+0x412/0x660 net/mptcp/subflow.c:1471
Code: 88 38 f7 0f 0b e9 4e fd ff ff e8 89 88 38 f7 48 89 df 48 83 c4 10 5b 41 5c 41 5d 41 5e 41 5f 5d e9 83 0d 00 00 e8 6e 88 38 f7 <0f> 0b e9 3f fe ff ff 44 89 f9 80 e1 07 38 c1 0f 8c 36 fc ff ff 4c
RSP: 0018:ffffc90000006758 EFLAGS: 00010246
RAX: ffffffff8a4d0852 RBX: ffff88802d76db00 RCX: ffff88802bcf1e00
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffff8880765608e7 R09: 1ffff1100ecac11c
R10: dffffc0000000000 R11: ffffed100ecac11d R12: ffff888076560000
R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c3e2065 CR3: 00000000610f3000 CR4: 00000000003506f0
Call Trace:
<IRQ>
tcp_data_queue+0x21b2/0x5a80 net/ipv4/tcp_input.c:5226
tcp_rcv_state_process+0x2772/0x4130 net/ipv4/tcp_input.c:6858
tcp_v6_do_rcv+0xc46/0x12d0 net/ipv6/tcp_ipv6.c:1503
tcp_v6_rcv+0x1fd4/0x26a0 net/ipv6/tcp_ipv6.c:1743
ip6_protocol_deliver_rcu+0xb7a/0x13c0 net/ipv6/ip6_input.c:438
ip6_input_finish+0x184/0x2c0 net/ipv6/ip6_input.c:483
NF_HOOK+0x303/0x390 include/linux/netfilter.h:304
ip_sabotage_in+0x1f4/0x280 net/bridge/br_netfilter_hooks.c:1001
nf_hook_entry_hookfn include/linux/netfilter.h:144 [inline]
nf_hook_slow+0xbd/0x200 net/netfilter/core.c:626
nf_hook include/linux/netfilter.h:259 [inline]
NF_HOOK+0x204/0x390 include/linux/netfilter.h:302
__netif_receive_skb_one_core net/core/dev.c:5608 [inline]
__netif_receive_skb+0xcc/0x290 net/core/dev.c:5722
netif_receive_skb_internal net/core/dev.c:5808 [inline]
netif_receive_skb+0x1bc/0x6f0 net/core/dev.c:5867
NF_HOOK+0x9a/0x380 include/linux/netfilter.h:304
br_handle_frame_finish+0xf31/0x1950 net/bridge/br_input.c:208
br_nf_hook_thresh+0x3b6/0x480 net/bridge/br_netfilter_hooks.c:1184
br_nf_pre_routing_finish_ipv6+0x9e3/0xd90 net/bridge/br_netfilter_ipv6.c:-1
NF_HOOK include/linux/netfilter.h:304 [inline]
br_nf_pre_routing_ipv6+0x34d/0x680 net/bridge/br_netfilter_ipv6.c:184
nf_hook_entry_hookfn include/linux/netfilter.h:144 [inline]
nf_hook_bridge_pre net/bridge/br_input.c:277 [inline]
br_handle_frame+0x957/0x14c0 net/bridge/br_input.c:424
__netif_receive_skb_core+0xf6b/0x3ac0 net/core/dev.c:5502
__netif_receive_skb_one_core net/core/dev.c:5606 [inline]
__netif_receive_skb+0x74/0x290 net/core/dev.c:5722
process_backlog+0x380/0x6e0 net/core/dev.c:6050
__napi_poll+0xc0/0x460 net/core/dev.c:6612
napi_poll net/core/dev.c:6679 [inline]
net_rx_action+0x5ea/0xbf0 net/core/dev.c:6815
handle_softirqs+0x280/0x820 kernel/softirq.c:578
do_softirq+0xed/0x180 kernel/softirq.c:479
</IRQ>
<TASK>
__local_bh_enable_ip+0x178/0x1c0 kernel/softirq.c:406
local_bh_enable include/linux/bottom_half.h:33 [inline]
rcu_read_unlock_bh include/linux/rcupdate.h:856 [inline]
__dev_queue_xmit+0x1449/0x35a0 net/core/dev.c:4452
neigh_output include/net/neighbour.h:543 [inline]
ip6_finish_output2+0xe2e/0x1650 net/ipv6/ip6_output.c:141
dst_output include/net/dst.h:467 [inline]
NF_HOOK include/linux/netfilter.h:304 [inline]
ip6_xmit+0x10aa/0x1840 net/ipv6/ip6_output.c:360
inet6_csk_xmit+0x472/0x710 net/ipv6/inet6_connection_sock.c:135
__tcp_transmit_skb+0x1c97/0x32a0 net/ipv4/tcp_output.c:1422
tcp_transmit_skb net/ipv4/tcp_output.c:1440 [inline]
tcp_write_xmit+0x174c/0x62e0 net/ipv4/tcp_output.c:2778
__tcp_push_pending_frames+0x97/0x340 net/ipv4/tcp_output.c:2963
tcp_sendmsg_locked+0x4286/0x4af0 net/ipv4/tcp.c:1312
tcp_sendmsg+0x2f/0x50 net/ipv4/tcp.c:1344
sock_sendmsg_nosec net/socket.c:730 [inline]
__sock_sendmsg net/socket.c:745 [inline]
sock_sendmsg+0x225/0x370 net/socket.c:768
rds_tcp_xmit+0x617/0xb50 net/rds/tcp_send.c:125
rds_send_xmit+0x1258/0x2600 net/rds/send.c:366
rds_send_worker+0x7d/0x2c0 net/rds/threads.c:200
process_one_work kernel/workqueue.c:2634 [inline]
process_scheduled_works+0xa45/0x15b0 kernel/workqueue.c:2711
worker_thread+0xa55/0xfc0 kernel/workqueue.c:2792
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
</TASK>


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 5fa4793a2d2d Linux 6.6.119
git tree: linux-6.6.y

console output: https://syzkaller.appspot.com/x/log.txt?x=15513a1a580000

kernel config: https://syzkaller.appspot.com/x/.config?x=691a6769a86ac817
dashboard link: https://syzkaller.appspot.com/bug?extid=32c1241cc455e5d3fc88
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1717deb4580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13513a1a580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/63699875f1dd/disk-5fa4793a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8506652fcb6f/vmlinux-5fa4793a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1b30ceed1710/bzImage-5fa4793a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+32c124...@syzkaller.appspotmail.com

------------[ cut here ]------------

WARNING: CPU: 1 PID: 11 at net/mptcp/subflow.c:1472 subflow_data_ready+0x412/0x660 net/mptcp/subflow.c:1471
Modules linked in:
CPU: 1 PID: 11 Comm: kworker/u4:0 Not tainted syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: krdsd rds_send_worker
RIP: 0010:subflow_data_ready+0x412/0x660 net/mptcp/subflow.c:1471
Code: 88 38 f7 0f 0b e9 4e fd ff ff e8 89 88 38 f7 48 89 df 48 83 c4 10 5b 41 5c 41 5d 41 5e 41 5f 5d e9 83 0d 00 00 e8 6e 88 38 f7 <0f> 0b e9 3f fe ff ff 44 89 f9 80 e1 07 38 c1 0f 8c 36 fc ff ff 4c

RSP: 0018:ffffc900001ef758 EFLAGS: 00010246
RAX: ffffffff8a4d0852 RBX: ffff88807d18ce00 RCX: ffff88801be43c00

RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000000

RBP: 0000000000000000 R08: ffff88802f5f9567 R09: 1ffff11005ebf2ac
R10: dffffc0000000000 R11: ffffed1005ebf2ad R12: ffff88802f5f8c80

R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000000

FS: 0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 000055555f992808 CR3: 0000000079cf8000 CR4: 00000000003506e0

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.