GRED: Unable to relocate VQ 0x0 after dequeue, screwing up backlog
------------[ cut here ]------------
WARNING: CPU: 0 PID: 1316 at net/mptcp/subflow.c:1528 subflow_data_ready+0x4b8/0x7e0 net/mptcp/subflow.c:1527
Modules linked in:
CPU: 0 UID: 0 PID: 1316 Comm: kworker/u8:5 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: krdsd rds_tcp_accept_worker
RIP: 0010:subflow_data_ready+0x4b8/0x7e0 net/mptcp/subflow.c:1527
Code: 0f 0b 90 90 e9 bc fc ff ff e8 b4 7b 8b f6 48 89 df 48 83 c4 08 5b 41 5c 41 5d 41 5e 41 5f 5d e9 6e 0e 00 00 e8 99 7b 8b f6 90 <0f> 0b 90 e9 e5 fd ff ff 90 0f 0b 90 43 0f b6 04 2f 84 c0 0f 85 a1
RSP: 0018:ffffc90000007100 EFLAGS: 00010246
RAX: ffffffff8b348817 RBX: ffff888057c83500 RCX: ffff888027201e40
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffff88807659094f R09: 1ffff1100ecb2129
R10: dffffc0000000000 R11: ffffed100ecb212a R12: 0000000000000000
R13: dffffc0000000000 R14: ffff888076590000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff888126131000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000002dc6c000 CR4: 00000000003526f0
Call Trace:
 <IRQ>
 tcp_data_queue+0x201e/0x6590 net/ipv4/tcp_input.c:5461
 tcp_rcv_established+0x1335/0x2670 net/ipv4/tcp_input.c:6474
 tcp_v6_do_rcv+0x8eb/0x1ba0 net/ipv6/tcp_ipv6.c:1607
 tcp_v6_rcv+0x2247/0x2ae0 net/ipv6/tcp_ipv6.c:1877
 ip6_protocol_deliver_rcu+0xcb0/0x15c0 net/ipv6/ip6_input.c:438
 ip6_input_finish+0x191/0x370 net/ipv6/ip6_input.c:489
 NF_HOOK+0x30c/0x3a0 include/linux/netfilter.h:318
 ip6_input+0x16a/0x270 net/ipv6/ip6_input.c:500
 NF_HOOK+0x30c/0x3a0 include/linux/netfilter.h:318
 __netif_receive_skb_one_core net/core/dev.c:6137 [inline]
 __netif_receive_skb+0xd3/0x380 net/core/dev.c:6250
 process_backlog+0x622/0x1530 net/core/dev.c:6602
 __napi_poll+0xae/0x320 net/core/dev.c:7666
 napi_poll net/core/dev.c:7729 [inline]
 net_rx_action+0x672/0xe50 net/core/dev.c:7881
 handle_softirqs+0x286/0x870 kernel/softirq.c:622
 do_softirq+0xec/0x180 kernel/softirq.c:523
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0x17d/0x1c0 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+0x1987/0x3180 net/core/dev.c:4844
 dev_queue_xmit include/linux/netdevice.h:3368 [inline]
 neigh_hh_output include/net/neighbour.h:540 [inline]
 neigh_output include/net/neighbour.h:554 [inline]
 ip6_finish_output2+0xf70/0x1480 net/ipv6/ip6_output.c:136
 NF_HOOK_COND include/linux/netfilter.h:307 [inline]
 ip6_output+0x340/0x550 net/ipv6/ip6_output.c:247
 NF_HOOK include/linux/netfilter.h:318 [inline]
 ip6_xmit+0x11b5/0x1970 net/ipv6/ip6_output.c:371
 inet6_csk_xmit+0x4db/0x780 net/ipv6/inet6_connection_sock.c:120
 __tcp_transmit_skb+0x2092/0x3aa0 net/ipv4/tcp_output.c:1631
 tcp_transmit_skb net/ipv4/tcp_output.c:1649 [inline]
 tcp_write_xmit+0x16e8/0x6940 net/ipv4/tcp_output.c:3002
 __tcp_push_pending_frames+0x97/0x360 net/ipv4/tcp_output.c:3185
 __tcp_close+0x617/0xfe0 net/ipv4/tcp.c:3208
 tcp_close+0x28/0x110 net/ipv4/tcp.c:3299
 inet_release+0x144/0x190 net/ipv4/af_inet.c:437
 __sock_release net/socket.c:662 [inline]
 sock_release+0x85/0x150 net/socket.c:690
 rds_tcp_accept_one+0x71a/0x930 net/rds/tcp_listen.c:214
 rds_tcp_accept_worker+0x3e/0xa0 net/rds/tcp.c:529
 process_one_work kernel/workqueue.c:3263 [inline]
 process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3346
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>