------------[ cut here ]------------
refcount_t: addition on 0; use-after-free.
WARNING: CPU: 0 PID: 6615 at lib/refcount.c:25 refcount_warn_saturate+0xfa/0x1d0 lib/refcount.c:25
Modules linked in:
CPU: 0 UID: 0 PID: 6615 Comm: syz.3.194 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:refcount_warn_saturate+0xfa/0x1d0 lib/refcount.c:25
Code: 00 00 e8 c9 83 3e fd 5b 41 5e c3 cc cc cc cc cc e8 bb 83 3e fd c6 05 4d d8 61 0a 01 90 48 c7 c7 60 9c 3e 8b e8 27 cc 02 fd 90 <0f> 0b 90 90 eb d7 e8 9b 83 3e fd c6 05 2e d8 61 0a 01 90 48 c7 c7
RSP: 0018:ffffc90003e962b8 EFLAGS: 00010246
RAX: 55807c67d2116b00 RBX: 0000000000000002 RCX: ffff888024b08000
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000100
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000100
R10: dffffc0000000000 R11: ffffed101710487b R12: dffffc0000000000
R13: ffffc90003e963a0 R14: ffff888031aa9e80 R15: dffffc0000000000
FS:  000055555ae47500(0000) GS:ffff888126bcb000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2f722ff8 CR3: 00000000207d4000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 __refcount_add include/linux/refcount.h:-1 [inline]
 __refcount_inc include/linux/refcount.h:366 [inline]
 refcount_inc include/linux/refcount.h:383 [inline]
 sock_hold include/net/sock.h:816 [inline]
 mptcp_schedule_work+0x164/0x1a0 net/mptcp/protocol.c:934
 mptcp_incoming_options+0x1059/0x1f60 net/mptcp/options.c:1163
 tcp_reset+0xe5/0x390 net/ipv4/tcp_input.c:4636
 tcp_validate_incoming+0x15d5/0x22a0 net/ipv4/tcp_input.c:6224
 tcp_rcv_state_process+0x611/0x44d0 net/ipv4/tcp_input.c:6978
 tcp_v4_do_rcv+0x3fb/0xbf0 net/ipv4/tcp_ipv4.c:1954
 tcp_v4_rcv+0x252a/0x2dc0 net/ipv4/tcp_ipv4.c:2374
 ip_protocol_deliver_rcu+0x221/0x440 net/ipv4/ip_input.c:205
 ip_local_deliver_finish+0x3bb/0x6f0 net/ipv4/ip_input.c:239
 NF_HOOK+0x309/0x3a0 include/linux/netfilter.h:318
 NF_HOOK+0x309/0x3a0 include/linux/netfilter.h:318
 __netif_receive_skb_one_core net/core/dev.c:6079 [inline]
 __netif_receive_skb+0x143/0x380 net/core/dev.c:6192
 process_backlog+0x31e/0x900 net/core/dev.c:6544
 __napi_poll+0xb6/0x540 net/core/dev.c:7594
 napi_poll net/core/dev.c:7657 [inline]
 net_rx_action+0x5f7/0xda0 net/core/dev.c:7784
 handle_softirqs+0x22f/0x710 kernel/softirq.c:622
 __do_softirq kernel/softirq.c:656 [inline]
 __local_bh_enable_ip+0x1a0/0x2e0 kernel/softirq.c:302
 local_bh_enable include/linux/bottom_half.h:33 [inline]
 rcu_read_unlock_bh include/linux/rcupdate.h:936 [inline]
 __dev_queue_xmit+0x1d3d/0x3b70 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]
 ip_finish_output2+0xd5a/0x11d0 net/ipv4/ip_output.c:237
 NF_HOOK_COND include/linux/netfilter.h:307 [inline]
 ip_output+0x29f/0x450 net/ipv4/ip_output.c:438
 ip_local_out net/ipv4/ip_output.c:131 [inline]
 __ip_queue_xmit+0x118d/0x1c30 net/ipv4/ip_output.c:534
 __tcp_transmit_skb+0x24f6/0x3aa0 net/ipv4/tcp_output.c:1628
 tcp_transmit_skb net/ipv4/tcp_output.c:1646 [inline]
 tcp_send_active_reset+0x35f/0x6d0 net/ipv4/tcp_output.c:3817
 tcp_disconnect+0x192/0x1fd0 net/ipv4/tcp.c:3366
 __tcp_close+0x676/0x1010 net/ipv4/tcp.c:3175
 __mptcp_close_ssk+0x3d7/0xfd0 net/mptcp/protocol.c:2460
 mptcp_do_fastclose+0x175/0x1f0 net/mptcp/protocol.c:2744
 __mptcp_unaccepted_force_close+0x29/0x40 net/mptcp/protocol.c:3039
 mptcp_subflow_queue_clean+0x20b/0x410 net/mptcp/subflow.c:1916
 mptcp_check_listen_stop+0x1be/0x2b0 net/mptcp/protocol.c:3062
 __mptcp_close+0xf6/0xa60 net/mptcp/protocol.c:3078
 mptcp_close+0x28/0x1a0 net/mptcp/protocol.c:3144
 inet_release+0x141/0x190 net/ipv4/af_inet.c:437
 __sock_release net/socket.c:662 [inline]
 sock_close+0xc3/0x240 net/socket.c:1455
 __fput+0x458/0xa80 fs/file_table.c:468
 task_work_run+0x1d4/0x260 kernel/task_work.c:227
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop+0xe9/0x130 kernel/entry/common.c:43
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
 do_syscall_64+0x2bd/0xfa0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fbae6fdeec9
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:00007ffc6312ca58 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007fbae7237da0 RCX: 00007fbae6fdeec9
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007fbae7237da0 R08: 000000000001b564 R09: 0000000f6312cd4f
R10: 00007fbae7237cb0 R11: 0000000000000246 R12: 00000000000348c4
R13: 00007ffc6312cb50 R14: ffffffffffffffff R15: 00007ffc6312cb70
 </TASK>