======================================================
WARNING: possible circular locking dependency detected
6.0.0-next-20221014 #1 Not tainted
------------------------------------------------------
syz-executor.5/22374 is trying to acquire lock:
ffff8880174ec070 ((work_completion)(&(&conn->timeout_work)->work)){+.+.}-{0:0}, at: __flush_work+0xdd/0xd00

but task is already holding lock:
ffffffff859dfee8 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_conn_hash_flush+0xc7/0x230

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (hci_cb_list_lock){+.+.}-{3:3}:
       __mutex_lock+0x136/0x14d0
       hci_remote_features_evt+0x47a/0x990
       hci_event_packet+0x919/0xf60
       hci_rx_work+0xa82/0x1000
       process_one_work+0xa17/0x16a0
       worker_thread+0x637/0x1260
       kthread+0x2ed/0x3a0
       ret_from_fork+0x22/0x30

-> #2 (&hdev->lock){+.+.}-{3:3}:
       __mutex_lock+0x136/0x14d0
       sco_sock_connect+0x1e4/0xa60
       __sys_connect_file+0x155/0x1a0
       __sys_connect+0x165/0x1a0
       __x64_sys_connect+0x6f/0xb0
       do_syscall_64+0x3b/0x90
       entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #1 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}:
       lock_sock_nested+0x3d/0xf0
       sco_sock_timeout+0xc3/0x230
       process_one_work+0xa17/0x16a0
       worker_thread+0x637/0x1260
       kthread+0x2ed/0x3a0
       ret_from_fork+0x22/0x30

-> #0 ((work_completion)(&(&conn->timeout_work)->work)){+.+.}-{0:0}:
       __lock_acquire+0x2a02/0x5e70
       lock_acquire+0x1a2/0x530
       __flush_work+0x105/0xd00
       __cancel_work_timer+0x39c/0x4e0
       sco_conn_del+0x1e4/0x2c0
       sco_disconn_cfm+0x62/0x80
       hci_conn_hash_flush+0x119/0x230
       hci_dev_close_sync+0x57b/0xfe0
       hci_unregister_dev+0x10f/0x380
       vhci_release+0x7c/0xf0
       __fput+0x263/0xa40
       task_work_run+0x170/0x280
       do_exit+0xb21/0x27f0
       do_group_exit+0xd0/0x2a0
       __x64_sys_exit_group+0x3a/0x50
       do_syscall_64+0x3b/0x90
       entry_SYSCALL_64_after_hwframe+0x63/0xcd

other info that might help us debug this:

Chain exists of:
  (work_completion)(&(&conn->timeout_work)->work) --> &hdev->lock --> hci_cb_list_lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(hci_cb_list_lock);
                               lock(&hdev->lock);
                               lock(hci_cb_list_lock);
  lock((work_completion)(&(&conn->timeout_work)->work));

 *** DEADLOCK ***

3 locks held by syz-executor.5/22374:
 #0: ffff888044131028 (&hdev->req_lock){+.+.}-{3:3}, at: hci_unregister_dev+0x107/0x380
 #1: ffff888044130078 (&hdev->lock){+.+.}-{3:3}, at: hci_dev_close_sync+0x2e0/0xfe0
 #2: ffffffff859dfee8 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_conn_hash_flush+0xc7/0x230

stack backtrace:
CPU: 0 PID: 22374 Comm: syz-executor.5 Not tainted 6.0.0-next-20221014 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x8b/0xb3
 check_noncircular+0x263/0x2e0
 __lock_acquire+0x2a02/0x5e70
 lock_acquire+0x1a2/0x530
 __flush_work+0x105/0xd00
 __cancel_work_timer+0x39c/0x4e0
 sco_conn_del+0x1e4/0x2c0
 sco_disconn_cfm+0x62/0x80
 hci_conn_hash_flush+0x119/0x230
 hci_dev_close_sync+0x57b/0xfe0
 hci_unregister_dev+0x10f/0x380
 vhci_release+0x7c/0xf0
 __fput+0x263/0xa40
 task_work_run+0x170/0x280
 do_exit+0xb21/0x27f0
 do_group_exit+0xd0/0x2a0
 __x64_sys_exit_group+0x3a/0x50
 do_syscall_64+0x3b/0x90
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7fd3a5eabb19
Code: Unable to access opcode bytes at 0x7fd3a5eabaef.
RSP: 002b:00007ffc4fbf61d8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00000000000000ae RCX: 00007fd3a5eabb19
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000043
RBP: 0000000000000000 R08: 0000000000000014 R09: 00000000000000ae
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fd3a5f060c3
R13: 0000000000000000 R14: 0000000000000003 R15: 00007ffc4fbf63c0
 </TASK>
Bluetooth: hci6: unexpected cc 0x0c03 length: 249 > 1
Bluetooth: hci6: unexpected cc 0x1003 length: 249 > 9
Bluetooth: hci6: unexpected cc 0x1001 length: 249 > 9
Bluetooth: hci6: unexpected cc 0x0c23 length: 249 > 4
Bluetooth: hci6: unexpected cc 0x0c25 length: 249 > 3
Bluetooth: hci6: unexpected cc 0x0c38 length: 249 > 2
Bluetooth: hci6: HCI_REQ-0x0c1a
Bluetooth: hci6: command 0x0409 tx timeout
Bluetooth: hci6: command 0x041b tx timeout
Bluetooth: hci6: command 0x040f tx timeout