======================================================
WARNING: possible circular locking dependency detected
6.16.0-syzkaller-11895-gcca7a0aae895-dirty #0 Not tainted
------------------------------------------------------
syz.1.13/5956 is trying to acquire lock:
ffff888021485840 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}, at: __flush_work+0xd2/0xbc0

but task is already holding lock:
ffff888021485b38 (&conn->lock#2){+.+.}-{4:4}, at: l2cap_conn_del+0x70/0x680

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&conn->lock#2){+.+.}-{4:4}:
       lock_acquire+0x120/0x360
       __mutex_lock+0x187/0x1360
       l2cap_info_timeout+0x60/0xa0
       process_scheduled_works+0xae1/0x17b0
       worker_thread+0x8a0/0xda0
       kthread+0x711/0x8a0
       ret_from_fork+0x3fc/0x770
       ret_from_fork_asm+0x1a/0x30

-> #0 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}:
       validate_chain+0xb9b/0x2140
       __lock_acquire+0xab9/0xd20
       lock_acquire+0x120/0x360
       __flush_work+0x6b8/0xbc0
       __cancel_work_sync+0xbe/0x110
       l2cap_conn_del+0x4f0/0x680
       hci_conn_hash_flush+0x10d/0x230
       hci_dev_close_sync+0xaef/0x1330
       hci_dev_do_close+0x2f/0x90
       hci_rfkill_set_block+0x21d/0x2e0
       rfkill_set_block+0x1d2/0x440
       rfkill_fop_write+0x44b/0x570
       vfs_write+0x27e/0xa90
       ksys_write+0x145/0x250
       do_syscall_64+0xfa/0x3b0
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&conn->lock#2);
                               lock((work_completion)(&(&conn->info_timer)->work));
                               lock(&conn->lock#2);
  lock((work_completion)(&(&conn->info_timer)->work));

 *** DEADLOCK ***

6 locks held by syz.1.13/5956:
 #0: ffffffff8f80e028 (rfkill_global_mutex){+.+.}-{4:4}, at: rfkill_fop_write+0x191/0x570
 #1: ffff888027ac4dc0 (&hdev->req_lock){+.+.}-{4:4}, at: hci_dev_do_close+0x27/0x90
 #2: ffff888027ac40b8 (&hdev->lock){+.+.}-{4:4}, at: hci_dev_close_sync+0x66a/0x1330
 #3: ffffffff8f6991c8 (hci_cb_list_lock){+.+.}-{4:4}, at: hci_conn_hash_flush+0xa1/0x230
 #4: ffff888021485b38 (&conn->lock#2){+.+.}-{4:4}, at: l2cap_conn_del+0x70/0x680
 #5: ffffffff8e139ee0 (rcu_read_lock){....}-{1:3}, at: __flush_work+0xd2/0xbc0

stack backtrace:
CPU: 0 UID: 0 PID: 5956 Comm: syz.1.13 Not tainted 6.16.0-syzkaller-11895-gcca7a0aae895-dirty #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250
 print_circular_bug+0x2ee/0x310
 check_noncircular+0x134/0x160
 validate_chain+0xb9b/0x2140
 __lock_acquire+0xab9/0xd20
 lock_acquire+0x120/0x360
 __flush_work+0x6b8/0xbc0
 __cancel_work_sync+0xbe/0x110
 l2cap_conn_del+0x4f0/0x680
 hci_conn_hash_flush+0x10d/0x230
 hci_dev_close_sync+0xaef/0x1330
 hci_dev_do_close+0x2f/0x90
 hci_rfkill_set_block+0x21d/0x2e0
 rfkill_set_block+0x1d2/0x440
 rfkill_fop_write+0x44b/0x570
 vfs_write+0x27e/0xa90
 ksys_write+0x145/0x250
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f7f7b58ebe9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f7f7c370038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f7f7b7b5fa0 RCX: 00007f7f7b58ebe9
RDX: 0000000000000008 RSI: 0000200000000080 RDI: 0000000000000006
RBP: 00007f7f7b611e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7f7b7b6038 R14: 00007f7f7b7b5fa0 R15: 00007ffff15f9128
 </TASK>
