------------[ cut here ]------------
WARNING: net/mptcp/subflow.c:1528 at subflow_data_ready+0x49b/0x7c0 net/mptcp/subflow.c:1527, CPU#0: syz.0.0/5339
Modules linked in:
CPU: 0 UID: 0 PID: 5339 Comm: syz.0.0 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
RIP: 0010:subflow_data_ready+0x49b/0x7c0 net/mptcp/subflow.c:1527
Code: 48 0f b9 3a e9 c9 fc ff ff e8 f1 e4 77 f6 48 89 df 48 83 c4 08 5b 41 5c 41 5d 41 5e 41 5f 5d e9 6b 0e 00 00 e8 d6 e4 77 f6 90 <0f> 0b 90 e9 f2 fd ff ff 90 0f 0b 90 43 0f b6 04 2f 84 c0 0f 85 a1
RSP: 0018:ffffc9000ec67760 EFLAGS: 00010293
RAX: ffffffff8b49dbca RBX: ffff88804168c240 RCX: ffff88801c608000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffff88801c66094f R09: 1ffff110038cc129
R10: dffffc0000000000 R11: ffffed10038cc12a R12: 0000000000000000
R13: dffffc0000000000 R14: ffff88801c660000 R15: 0000000000000000
FS:  00007f62ad6a46c0(0000) GS:ffff88808d22a000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffef2208ff8 CR3: 0000000040595000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 tcp_data_queue+0x1e14/0x5e30 net/ipv4/tcp_input.c:5461
 tcp_rcv_established+0xf57/0x2580 net/ipv4/tcp_input.c:6474
 tcp_v4_do_rcv+0xa90/0x1430 net/ipv4/tcp_ipv4.c:1881
 sk_backlog_rcv include/net/sock.h:1177 [inline]
 __release_sock+0x265/0x3a0 net/core/sock.c:3213
 release_sock+0x5f/0x1f0 net/core/sock.c:3795
 mptcp_connect+0x5be/0x860 net/mptcp/protocol.c:3985
 __inet_stream_connect+0x298/0xf00 net/ipv4/af_inet.c:679
 inet_stream_connect+0x66/0xa0 net/ipv4/af_inet.c:750
 __sys_connect_file net/socket.c:2089 [inline]
 __sys_connect+0x316/0x440 net/socket.c:2108
 __do_sys_connect net/socket.c:2114 [inline]
 __se_sys_connect net/socket.c:2111 [inline]
 __x64_sys_connect+0x7a/0x90 net/socket.c:2111
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f62ac78f7c9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f62ad6a4038 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 00007f62ac9e5fa0 RCX: 00007f62ac78f7c9
RDX: 000000000000001c RSI: 0000200000000040 RDI: 0000000000000003
RBP: 00007f62ac813f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f62ac9e6038 R14: 00007f62ac9e5fa0 R15: 00007ffe193a9228
 </TASK>