======================================================
WARNING: possible circular locking dependency detected
6.1.0-rc5-syzkaller-01316-g170d97739de4 #0 Not tainted
------------------------------------------------------
syz-executor.2/32217 is trying to acquire lock:
ffff8880451dbb30 (k-sk_lock-AF_INET){+.+.}-{0:0}, at: sk_common_release+0x68/0x390 net/core/sock.c:3662

but task is already holding lock:
ffff8880451dbdb8 (k-clock-AF_INET){+++.}-{2:2}, at: l2tp_tunnel_register+0x126/0x1210 net/l2tp/l2tp_core.c:1477

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (k-clock-AF_INET){+++.}-{2:2}:
       __raw_write_lock_bh include/linux/rwlock_api_smp.h:202 [inline]
       _raw_write_lock_bh+0x33/0x40 kernel/locking/spinlock.c:334
       sock_orphan include/net/sock.h:2090 [inline]
       dccp_close+0x4c8/0xd60 net/dccp/proto.c:1045
       inet_release+0x132/0x270 net/ipv4/af_inet.c:428
       __sock_release net/socket.c:650 [inline]
       sock_release+0x8b/0x1b0 net/socket.c:678
       inet_ctl_sock_destroy include/net/inet_common.h:71 [inline]
       dccp_v4_exit_net+0x15a/0x2c0 net/dccp/ipv4.c:1050
       ops_exit_list+0xb0/0x170 net/core/net_namespace.c:169
       cleanup_net+0x4ee/0xb10 net/core/net_namespace.c:606
       process_one_work+0x9bf/0x1710 kernel/workqueue.c:2289
       worker_thread+0x669/0x1090 kernel/workqueue.c:2436
       kthread+0x2e8/0x3a0 kernel/kthread.c:376
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306

-> #0 (k-sk_lock-AF_INET){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3097 [inline]
       check_prevs_add kernel/locking/lockdep.c:3216 [inline]
       validate_chain kernel/locking/lockdep.c:3831 [inline]
       __lock_acquire+0x2a43/0x56d0 kernel/locking/lockdep.c:5055
       lock_acquire kernel/locking/lockdep.c:5668 [inline]
       lock_acquire+0x1e3/0x630 kernel/locking/lockdep.c:5633
       lock_sock_fast include/net/sock.h:1753 [inline]
       udp_destroy_sock+0x34/0x250 net/ipv4/udp.c:2661
       sk_common_release+0x68/0x390 net/core/sock.c:3662
       inet_release+0x132/0x270 net/ipv4/af_inet.c:428
       __sock_release net/socket.c:650 [inline]
       sock_release+0x8b/0x1b0 net/socket.c:678
       l2tp_tunnel_register+0xc75/0x1210 net/l2tp/l2tp_core.c:1530
       l2tp_nl_cmd_tunnel_create+0x3d6/0x8b0 net/l2tp/l2tp_netlink.c:245
       genl_family_rcv_msg_doit.isra.0+0x1e6/0x2d0 net/netlink/genetlink.c:968
       genl_family_rcv_msg net/netlink/genetlink.c:1048 [inline]
       genl_rcv_msg+0x4ff/0x7e0 net/netlink/genetlink.c:1065
       netlink_rcv_skb+0x165/0x440 net/netlink/af_netlink.c:2564
       genl_rcv+0x28/0x40 net/netlink/genetlink.c:1076
       netlink_unicast_kernel net/netlink/af_netlink.c:1330 [inline]
       netlink_unicast+0x547/0x7f0 net/netlink/af_netlink.c:1356
       netlink_sendmsg+0x91b/0xe10 net/netlink/af_netlink.c:1932
       sock_sendmsg_nosec net/socket.c:714 [inline]
       sock_sendmsg+0xd3/0x120 net/socket.c:734
       ____sys_sendmsg+0x712/0x8c0 net/socket.c:2476
       ___sys_sendmsg+0x110/0x1b0 net/socket.c:2530
       __sys_sendmsg+0xf7/0x1c0 net/socket.c:2559
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x63/0xcd

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(k-clock-AF_INET);
                               lock(k-sk_lock-AF_INET);
                               lock(k-clock-AF_INET);
  lock(k-sk_lock-AF_INET);

 *** DEADLOCK ***

3 locks held by syz-executor.2/32217:
 #0: ffffffff8df53370 (cb_lock){++++}-{3:3}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1075
 #1: ffffffff8df53428 (genl_mutex){+.+.}-{3:3}, at: genl_lock net/netlink/genetlink.c:33 [inline]
 #1: ffffffff8df53428 (genl_mutex){+.+.}-{3:3}, at: genl_rcv_msg+0x51a/0x7e0 net/netlink/genetlink.c:1063
 #2: ffff8880451dbdb8 (k-clock-AF_INET){+++.}-{2:2}, at: l2tp_tunnel_register+0x126/0x1210 net/l2tp/l2tp_core.c:1477

stack backtrace:
CPU: 1 PID: 32217 Comm: syz-executor.2 Not tainted 6.1.0-rc5-syzkaller-01316-g170d97739de4 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xd1/0x138 lib/dump_stack.c:106
 check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2177
 check_prev_add kernel/locking/lockdep.c:3097 [inline]
 check_prevs_add kernel/locking/lockdep.c:3216 [inline]
 validate_chain kernel/locking/lockdep.c:3831 [inline]
 __lock_acquire+0x2a43/0x56d0 kernel/locking/lockdep.c:5055
 lock_acquire kernel/locking/lockdep.c:5668 [inline]
 lock_acquire+0x1e3/0x630 kernel/locking/lockdep.c:5633
 lock_sock_fast include/net/sock.h:1753 [inline]
 udp_destroy_sock+0x34/0x250 net/ipv4/udp.c:2661
 sk_common_release+0x68/0x390 net/core/sock.c:3662
 inet_release+0x132/0x270 net/ipv4/af_inet.c:428
 __sock_release net/socket.c:650 [inline]
 sock_release+0x8b/0x1b0 net/socket.c:678
 l2tp_tunnel_register+0xc75/0x1210 net/l2tp/l2tp_core.c:1530
 l2tp_nl_cmd_tunnel_create+0x3d6/0x8b0 net/l2tp/l2tp_netlink.c:245
 genl_family_rcv_msg_doit.isra.0+0x1e6/0x2d0 net/netlink/genetlink.c:968
 genl_family_rcv_msg net/netlink/genetlink.c:1048 [inline]
 genl_rcv_msg+0x4ff/0x7e0 net/netlink/genetlink.c:1065
 netlink_rcv_skb+0x165/0x440 net/netlink/af_netlink.c:2564
 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1076
 netlink_unicast_kernel net/netlink/af_netlink.c:1330 [inline]
 netlink_unicast+0x547/0x7f0 net/netlink/af_netlink.c:1356
 netlink_sendmsg+0x91b/0xe10 net/netlink/af_netlink.c:1932
 sock_sendmsg_nosec net/socket.c:714 [inline]
 sock_sendmsg+0xd3/0x120 net/socket.c:734
 ____sys_sendmsg+0x712/0x8c0 net/socket.c:2476
 ___sys_sendmsg+0x110/0x1b0 net/socket.c:2530
 __sys_sendmsg+0xf7/0x1c0 net/socket.c:2559
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f96d208c0d9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f96d2e82168 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f96d21abf80 RCX: 00007f96d208c0d9
RDX: 0000000000000000 RSI: 0000000020000240 RDI: 0000000000000003
RBP: 00007f96d20e7ae9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fff22263f3f R14: 00007f96d2e82300 R15: 0000000000022000
 </TASK>
BUG: sleeping function called from invalid context at net/core/sock.c:3493
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 32217, name: syz-executor.2
preempt_count: 1, expected: 0
RCU nest depth: 0, expected: 0
INFO: lockdep is turned off.
Preemption disabled at:
[<0000000000000000>] 0x0
CPU: 1 PID: 32217 Comm: syz-executor.2 Not tainted 6.1.0-rc5-syzkaller-01316-g170d97739de4 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xd1/0x138 lib/dump_stack.c:106
 __might_resched.cold+0x222/0x26b kernel/sched/core.c:9890
 __lock_sock_fast+0x25/0xe0 net/core/sock.c:3493
 lock_sock_fast include/net/sock.h:1755 [inline]
 udp_destroy_sock+0x3c/0x250 net/ipv4/udp.c:2661
 sk_common_release+0x68/0x390 net/core/sock.c:3662
 inet_release+0x132/0x270 net/ipv4/af_inet.c:428
 __sock_release net/socket.c:650 [inline]
 sock_release+0x8b/0x1b0 net/socket.c:678
 l2tp_tunnel_register+0xc75/0x1210 net/l2tp/l2tp_core.c:1530
 l2tp_nl_cmd_tunnel_create+0x3d6/0x8b0 net/l2tp/l2tp_netlink.c:245
 genl_family_rcv_msg_doit.isra.0+0x1e6/0x2d0 net/netlink/genetlink.c:968
 genl_family_rcv_msg net/netlink/genetlink.c:1048 [inline]
 genl_rcv_msg+0x4ff/0x7e0 net/netlink/genetlink.c:1065
 netlink_rcv_skb+0x165/0x440 net/netlink/af_netlink.c:2564
 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1076
 netlink_unicast_kernel net/netlink/af_netlink.c:1330 [inline]
 netlink_unicast+0x547/0x7f0 net/netlink/af_netlink.c:1356
 netlink_sendmsg+0x91b/0xe10 net/netlink/af_netlink.c:1932
 sock_sendmsg_nosec net/socket.c:714 [inline]
 sock_sendmsg+0xd3/0x120 net/socket.c:734
 ____sys_sendmsg+0x712/0x8c0 net/socket.c:2476
 ___sys_sendmsg+0x110/0x1b0 net/socket.c:2530
 __sys_sendmsg+0xf7/0x1c0 net/socket.c:2559
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f96d208c0d9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f96d2e82168 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f96d21abf80 RCX: 00007f96d208c0d9
RDX: 0000000000000000 RSI: 0000000020000240 RDI: 0000000000000003
RBP: 00007f96d20e7ae9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fff22263f3f R14: 00007f96d2e82300 R15: 0000000000022000
 </TASK>