loop7: detected capacity change from 0 to 264192
FAT-fs (loop7): Invalid FSINFO signature: 0x00000000, 0x00000000 (sector = 1)
======================================================
WARNING: possible circular locking dependency detected
6.1.0-next-20221214 #1 Not tainted
------------------------------------------------------
syz-executor.1/15410 is trying to acquire lock:
ffff88800ee2b070 ((work_completion)(&(&conn->timeout_work)->work)){+.+.}-{0:0}, at: __flush_work+0xdd/0xd00

but task is already holding lock:
ffffffff85be3e68 (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:

-> #3 (hci_cb_list_lock){+.+.}-{3:3}:
       __mutex_lock+0x136/0x14e0
       hci_connect_cfm+0x26/0x140
       hci_remote_features_evt+0x478/0x870
       hci_event_packet+0x91d/0xf60
       hci_rx_work+0xa86/0x1000
       process_one_work+0xa0f/0x1690
       worker_thread+0x63b/0x1260
       kthread+0x2f1/0x3a0
       ret_from_fork+0x2c/0x50

-> #2 (&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

-> #1 (sk_lock-AF_BLUETOOTH-BTPROTO_SCO){+.+.}-{0:0}:
       lock_sock_nested+0x41/0xf0
       sco_sock_timeout+0xc7/0x230
       process_one_work+0xa0f/0x1690
       worker_thread+0x63b/0x1260
       kthread+0x2f1/0x3a0
       ret_from_fork+0x2c/0x50

-> #0 ((work_completion)(&(&conn->timeout_work)->work)){+.+.}-{0:0}:
       __lock_acquire+0x2a02/0x5e70
       lock_acquire.part.0+0x11e/0x340
       __flush_work+0x109/0xd00
       __cancel_work_timer+0x39c/0x4e0
       sco_conn_del+0x1e4/0x2c0
       sco_disconn_cfm+0x66/0x80
       hci_conn_hash_flush+0x11d/0x230
       hci_dev_close_sync+0x57f/0xff0
       hci_unregister_dev+0x15e/0x410
       vhci_release+0x80/0x100
       __fput+0x263/0xa40
       task_work_run+0x174/0x280
       do_exit+0xaad/0x2760
       do_group_exit+0xd4/0x2a0
       get_signal+0x21b7/0x22f0
       arch_do_signal_or_restart+0x79/0x5a0
       exit_to_user_mode_prepare+0x131/0x1a0
       syscall_exit_to_user_mode+0x1d/0x50
       do_syscall_64+0x4c/0x90
       entry_SYSCALL_64_after_hwframe+0x72/0xdc

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.1/15410:
 #0: ffff888020fb9028 (&hdev->req_lock){+.+.}-{3:3}, at: hci_unregister_dev+0x156/0x410
 #1: ffff888020fb8078 (&hdev->lock){+.+.}-{3:3}, at: hci_dev_close_sync+0x2e4/0xff0
 #2: ffffffff85be3e68 (hci_cb_list_lock){+.+.}-{3:3}, at: hci_conn_hash_flush+0xcb/0x230

stack backtrace:
CPU: 1 PID: 15410 Comm: syz-executor.1 Not tainted 6.1.0-next-20221214 #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.part.0+0x11e/0x340
 __flush_work+0x109/0xd00
 __cancel_work_timer+0x39c/0x4e0
 sco_conn_del+0x1e4/0x2c0
 sco_disconn_cfm+0x66/0x80
 hci_conn_hash_flush+0x11d/0x230
 hci_dev_close_sync+0x57f/0xff0
 hci_unregister_dev+0x15e/0x410
 vhci_release+0x80/0x100
 __fput+0x263/0xa40
 task_work_run+0x174/0x280
 do_exit+0xaad/0x2760
 do_group_exit+0xd4/0x2a0
 get_signal+0x21b7/0x22f0
 arch_do_signal_or_restart+0x79/0x5a0
 exit_to_user_mode_prepare+0x131/0x1a0
 syscall_exit_to_user_mode+0x1d/0x50
 do_syscall_64+0x4c/0x90
 entry_SYSCALL_64_after_hwframe+0x72/0xdc
RIP: 0033:0x7f6d6fc6fb19
Code: Unable to access opcode bytes at 0x7f6d6fc6faef.
RSP: 002b:00007f6d6d1e5218 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f6d6fd82f68 RCX: 00007f6d6fc6fb19
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f6d6fd82f68
RBP: 00007f6d6fd82f60 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f6d6fd82f6c
R13: 00007ffc0546f62f R14: 00007f6d6d1e5300 R15: 0000000000022000
 </TASK>
Bluetooth: hci0: unexpected cc 0x0c03 length: 249 > 1
Bluetooth: hci0: unexpected cc 0x1003 length: 249 > 9
Bluetooth: hci0: unexpected cc 0x1001 length: 249 > 9
Bluetooth: hci0: unexpected cc 0x0c23 length: 249 > 4
Bluetooth: hci0: unexpected cc 0x0c25 length: 249 > 3
Bluetooth: hci0: unexpected cc 0x0c38 length: 249 > 2
Bluetooth: hci0: command 0x0409 tx timeout
Bluetooth: hci0: command 0x041b tx timeout
Bluetooth: hci0: command 0x040f tx timeout