------------[ cut here ]------------
WARNING: CPU: 0 PID: 15 at net/mptcp/subflow.c:1520 subflow_data_ready+0x4b8/0x7e0
Modules linked in:
CPU: 0 UID: 0 PID: 15 Comm: ksoftirqd/0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:subflow_data_ready+0x4b8/0x7e0
Code: 0f 0b 90 90 e9 bc fc ff ff e8 e4 94 58 f6 48 89 df 48 83 c4 08 5b 41 5c 41 5d 41 5e 41 5f 5d e9 6e 0e 00 00 e8 c9 94 58 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:ffffc90000126e80 EFLAGS: 00010246
RAX: ffffffff8b6718c7 RBX: ffff88803d5fe800 RCX: ffff88801c2fb980
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffff88802a7c3937 R09: 1ffff110054f8726
R10: dffffc0000000000 R11: ffffed10054f8727 R12: 0000000000000000
R13: dffffc0000000000 R14: ffff88802a7c3000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8880b8613000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb2f50e0020 CR3: 000000003e82c000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 tcp_data_queue+0x54b/0x6450
 tcp_rcv_state_process+0x23a4/0x44d0
 tcp_v4_do_rcv+0x3f2/0xce0
 tcp_v4_rcv+0x252a/0x2dc0
 ip_protocol_deliver_rcu+0x221/0x440
 ip_local_deliver_finish+0x3bb/0x6f0
 NF_HOOK+0x30c/0x3a0
 NF_HOOK+0x30c/0x3a0
 __netif_receive_skb+0x143/0x380
 process_backlog+0x60e/0x14f0
 __napi_poll+0xc7/0x360
 net_rx_action+0x707/0xe30
 handle_softirqs+0x286/0x870
 run_ksoftirqd+0x9b/0x100
 smpboot_thread_fn+0x542/0xa60
 kthread+0x711/0x8a0
 ret_from_fork+0x439/0x7d0
 ret_from_fork_asm+0x1a/0x30
 </TASK>
