============================================
WARNING: possible recursive locking detected
6.2.0-rc7-syzkaller-17907-g2d3827b3f393 #0 Not tainted
--------------------------------------------
syz-executor.4/18884 is trying to acquire lock:
ffff000118f35130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1725 [inline]
ffff000118f35130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: l2tp_tunnel_register+0x3c4/0x988 net/l2tp/l2tp_core.c:1483

but task is already holding lock:
ffff000118f35130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1725 [inline]
ffff000118f35130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: pppol2tp_connect+0x188/0x6c0 net/l2tp/l2tp_ppp.c:675

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

       CPU0
       ----
  lock(sk_lock-AF_PPPOX);
  lock(sk_lock-AF_PPPOX);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

1 lock held by syz-executor.4/18884:
 #0: ffff000118f35130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1725 [inline]
 #0: ffff000118f35130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: pppol2tp_connect+0x188/0x6c0 net/l2tp/l2tp_ppp.c:675

stack backtrace:
CPU: 1 PID: 18884 Comm: syz-executor.4 Not tainted 6.2.0-rc7-syzkaller-17907-g2d3827b3f393 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/21/2023
Call trace:
 dump_backtrace+0x1c8/0x1f4 arch/arm64/kernel/stacktrace.c:158
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xd0/0x124 lib/dump_stack.c:106
 dump_stack+0x1c/0x28 lib/dump_stack.c:113
 __lock_acquire+0x808/0x2f48
 lock_acquire+0x164/0x334 kernel/locking/lockdep.c:5668
 lock_sock_nested+0x70/0xd8 net/core/sock.c:3470
 lock_sock include/net/sock.h:1725 [inline]
 l2tp_tunnel_register+0x3c4/0x988 net/l2tp/l2tp_core.c:1483
 pppol2tp_connect+0x3f4/0x6c0 net/l2tp/l2tp_ppp.c:723
 __sys_connect_file net/socket.c:1976 [inline]
 __sys_connect+0x184/0x190 net/socket.c:1993
 __do_sys_connect net/socket.c:2003 [inline]
 __se_sys_connect net/socket.c:2000 [inline]
 __arm64_sys_connect+0x28/0x3c net/socket.c:2000
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x64/0x178 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0xbc/0x180 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x48/0x110 arch/arm64/kernel/syscall.c:193
 el0_svc+0x58/0x14c arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:591