============================================
WARNING: possible recursive locking detected
6.12.0-rc1-syzkaller-00010-gc05ad457ce8c #0 Not tainted
--------------------------------------------
syz.0.736/9831 is trying to acquire lock:
ff6000001a9bb1d8 (k-slock-AF_INET){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
ff6000001a9bb1d8 (k-slock-AF_INET){+.-.}-{2:2}, at: sk_clone_lock+0x34c/0x1154 net/core/sock.c:2396

but task is already holding lock:
ff6000001e84b4d8 (k-slock-AF_INET){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
ff6000001e84b4d8 (k-slock-AF_INET){+.-.}-{2:2}, at: sk_clone_lock+0x34c/0x1154 net/core/sock.c:2396

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(k-slock-AF_INET);
  lock(k-slock-AF_INET);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

7 locks held by syz.0.736/9831:
 #0: ff6000001a9ba658 (sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1609 [inline]
 #0: ff6000001a9ba658 (sk_lock-AF_INET){+.+.}-{0:0}, at: inet_stream_connect+0x48/0xa0 net/ipv4/af_inet.c:749
 #1: ff6000001e848f18 (k-sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1609 [inline]
 #1: ff6000001e848f18 (k-sk_lock-AF_INET){+.+.}-{0:0}, at: mptcp_connect+0x4e0/0xf42 net/mptcp/protocol.c:3760
 #2: ffffffff87fcc100 (rcu_read_lock){....}-{1:2}, at: read_pnet include/net/net_namespace.h:383 [inline]
 #2: ffffffff87fcc100 (rcu_read_lock){....}-{1:2}, at: sock_net include/net/sock.h:655 [inline]
 #2: ffffffff87fcc100 (rcu_read_lock){....}-{1:2}, at: __ip_queue_xmit+0x52/0x1b20 net/ipv4/ip_output.c:461
 #3: ffffffff87fcc100 (rcu_read_lock){....}-{1:2}, at: lwtunnel_xmit_redirect include/net/lwtunnel.h:98 [inline]
 #3: ffffffff87fcc100 (rcu_read_lock){....}-{1:2}, at: ip_finish_output2+0x456/0x2c48 net/ipv4/ip_output.c:222
 #4: ffffffff87fcc100 (rcu_read_lock){....}-{1:2}, at: local_lock_release include/linux/local_lock_internal.h:37 [inline]
 #4: ffffffff87fcc100 (rcu_read_lock){....}-{1:2}, at: process_backlog+0x482/0x1cbc net/core/dev.c:6105
 #5: ffffffff87fcc100 (rcu_read_lock){....}-{1:2}, at: __skb_pull include/linux/skbuff.h:2768 [inline]
 #5: ffffffff87fcc100 (rcu_read_lock){....}-{1:2}, at: ip_local_deliver_finish+0x216/0x57c net/ipv4/ip_input.c:230
 #6: ff6000001e84b4d8 (k-slock-AF_INET){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
 #6: ff6000001e84b4d8 (k-slock-AF_INET){+.-.}-{2:2}, at: sk_clone_lock+0x34c/0x1154 net/core/sock.c:2396

stack backtrace:
CPU: 1 UID: 0 PID: 9831 Comm: syz.0.736 Not tainted 6.12.0-rc1-syzkaller-00010-gc05ad457ce8c #0
Hardware name: riscv-virtio,qemu (DT)
Call Trace:
[<ffffffff80010a14>] dump_backtrace+0x2e/0x3c arch/riscv/kernel/stacktrace.c:130
[<ffffffff85f7c3cc>] show_stack+0x34/0x40 arch/riscv/kernel/stacktrace.c:136
[<ffffffff85fd797a>] __dump_stack lib/dump_stack.c:94 [inline]
[<ffffffff85fd797a>] dump_stack_lvl+0x122/0x196 lib/dump_stack.c:120
[<ffffffff85fd7a0a>] dump_stack+0x1c/0x24 lib/dump_stack.c:129
[<ffffffff80239486>] print_deadlock_bug+0x6ac/0x70a kernel/locking/lockdep.c:3037
[<ffffffff80242d5e>] check_deadlock kernel/locking/lockdep.c:3089 [inline]
[<ffffffff80242d5e>] validate_chain kernel/locking/lockdep.c:3891 [inline]
[<ffffffff80242d5e>] __lock_acquire+0x34e8/0x8320 kernel/locking/lockdep.c:5202
[<ffffffff80249eb6>] lock_acquire.part.0+0x2c6/0x81c kernel/locking/lockdep.c:5825
[<ffffffff8024a480>] lock_acquire+0x74/0x98 kernel/locking/lockdep.c:5798
[<ffffffff85ffb260>] __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
[<ffffffff85ffb260>] _raw_spin_lock+0x32/0x48 kernel/locking/spinlock.c:154
[<ffffffff84c78092>] spin_lock include/linux/spinlock.h:351 [inline]
[<ffffffff84c78092>] sk_clone_lock+0x34c/0x1154 net/core/sock.c:2396
[<ffffffff85e7411e>] mptcp_sk_clone_init+0x3e/0x1564 net/mptcp/protocol.c:3279
[<ffffffff85e844e2>] subflow_syn_recv_sock+0x11a4/0x1b24 net/mptcp/subflow.c:878
[<ffffffff854308c4>] tcp_check_req+0x9ac/0x21a2 net/ipv4/tcp_minisocks.c:858
[<ffffffff8542bf58>] tcp_v4_rcv+0x17ec/0x462e net/ipv4/tcp_ipv4.c:2271
[<ffffffff8532f57c>] ip_protocol_deliver_rcu+0xa2/0x64a net/ipv4/ip_input.c:205
[<ffffffff8532fe10>] ip_local_deliver_finish+0x2ec/0x57c net/ipv4/ip_input.c:233
[<ffffffff85330252>] NF_HOOK include/linux/netfilter.h:314 [inline]
[<ffffffff85330252>] NF_HOOK include/linux/netfilter.h:308 [inline]
[<ffffffff85330252>] ip_local_deliver+0x1b2/0x568 net/ipv4/ip_input.c:254
[<ffffffff8532ee32>] dst_input include/net/dst.h:460 [inline]
[<ffffffff8532ee32>] ip_rcv_finish+0x1b0/0x2d2 net/ipv4/ip_input.c:449
[<ffffffff853306de>] NF_HOOK include/linux/netfilter.h:314 [inline]
[<ffffffff853306de>] NF_HOOK include/linux/netfilter.h:308 [inline]
[<ffffffff853306de>] ip_rcv+0xd6/0x44e net/ipv4/ip_input.c:569
[<ffffffff84d21a54>] __netif_receive_skb_one_core+0x106/0x16e net/core/dev.c:5662
[<ffffffff84d21cd4>] __netif_receive_skb+0x2c/0x144 net/core/dev.c:5775
[<ffffffff84d22d58>] process_backlog+0x4fc/0x1cbc net/core/dev.c:6107
[<ffffffff84d2760a>] __napi_poll.constprop.0+0xaa/0x4b8 net/core/dev.c:6771
[<ffffffff84d2842a>] napi_poll net/core/dev.c:6840 [inline]
[<ffffffff84d2842a>] net_rx_action+0xa12/0xf10 net/core/dev.c:6962
[<ffffffff800e0fba>] handle_softirqs+0x4a6/0x10de kernel/softirq.c:554
[<ffffffff85ffccb8>] __do_softirq+0x12/0x1a kernel/softirq.c:588
[<ffffffff80006f74>] ___do_softirq+0x18/0x20 arch/riscv/kernel/irq.c:85
[<ffffffff85ffcc1a>] call_on_irq_stack+0x32/0x40 arch/riscv/kernel/entry.S:355