======================================================
WARNING: possible circular locking dependency detected
6.1.0-rc7-next-20221202 #1 Not tainted
------------------------------------------------------
syz-executor.6/6654 is trying to acquire lock:
ffff8880426f4130 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}, at: sco_conn_del+0x11c/0x2c0

but task is already holding lock:
ffffffff85be2f28 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_conn_hash_flush+0xcb/0x230

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (hci_cb_list_lock){+.+.}-{3:3}:
       __mutex_lock+0x136/0x14e0
       hci_remote_features_evt+0x47e/0x990
       hci_event_packet+0x91d/0xf60
       hci_rx_work+0xa86/0x1000
       process_one_work+0xa17/0x16a0
       worker_thread+0x63b/0x1260
       kthread+0x2f1/0x3a0
       ret_from_fork+0x2c/0x50

-> #1 (&hdev->lock){+.+.}-{3:3}:
       __mutex_lock+0x136/0x14e0
       sco_sock_connect+0x1e8/0xa60
       __sys_connect_file+0x159/0x1a0
       __sys_connect+0x169/0x1a0
       __x64_sys_connect+0x73/0xb0
       do_syscall_64+0x3f/0x90
       entry_SYSCALL_64_after_hwframe+0x72/0xdc

-> #0 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}:
       __lock_acquire+0x2a02/0x5e70
       lock_acquire+0x1a6/0x530
       lock_sock_nested+0x41/0xf0
       sco_conn_del+0x11c/0x2c0
       sco_disconn_cfm+0x66/0x80
       hci_conn_hash_flush+0x11d/0x230
       hci_dev_close_sync+0x57f/0xff0
       hci_unregister_dev+0x113/0x380
       vhci_release+0x80/0x100
       __fput+0x263/0xa40
       task_work_run+0x174/0x280
       do_exit+0xa8e/0x2720
       do_group_exit+0xd4/0x2a0
       __x64_sys_exit_group+0x3e/0x50
       do_syscall_64+0x3f/0x90
       entry_SYSCALL_64_after_hwframe+0x72/0xdc

other info that might help us debug this:

Chain exists of:
  sk_lock-AF_BLUETOOTH-BTPROTO_SCO --> &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(sk_lock-AF_BLUETOOTH-BTPROTO_SCO);

 *** DEADLOCK ***

3 locks held by syz-executor.6/6654:
 #0: ffff888045d35028 (&hdev->req_lock){+.+.}-{3:3}, at: hci_unregister_dev+0x10b/0x380
 #1: ffff888045d34078 (&hdev->lock){+.+.}-{3:3}, at: hci_dev_close_sync+0x2e4/0xff0
 #2: ffffffff85be2f28 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_conn_hash_flush+0xcb/0x230

stack backtrace:
CPU: 1 PID: 6654 Comm: syz-executor.6 Not tainted 6.1.0-rc7-next-20221202 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x8f/0xb7
 check_noncircular+0x263/0x2e0
 __lock_acquire+0x2a02/0x5e70
 lock_acquire+0x1a6/0x530
 lock_sock_nested+0x41/0xf0
 sco_conn_del+0x11c/0x2c0
 sco_disconn_cfm+0x66/0x80
 hci_conn_hash_flush+0x11d/0x230
 hci_dev_close_sync+0x57f/0xff0
 hci_unregister_dev+0x113/0x380
 vhci_release+0x80/0x100
 __fput+0x263/0xa40
 task_work_run+0x174/0x280
 do_exit+0xa8e/0x2720
 do_group_exit+0xd4/0x2a0
 __x64_sys_exit_group+0x3e/0x50
 do_syscall_64+0x3f/0x90
 entry_SYSCALL_64_after_hwframe+0x72/0xdc
RIP: 0033:0x7f028fe13b19
Code: Unable to access opcode bytes at 0x7f028fe13aef.
RSP: 002b:00007fffafa58568 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000064 RCX: 00007f028fe13b19
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 00007f028fe6d177 R08: 000000000000000c R09: 0000555555d903bc
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000016
R13: 00007fffafa59840 R14: 0000555555d903bc R15: 00007fffafa5a940
 </TASK>
cgroup: fork rejected by pids controller in /syz4
Bluetooth: hci4: Opcode 0x c03 failed: -110
Bluetooth: hci4: Opcode 0x c03 failed: -110