======================================================
WARNING: possible circular locking dependency detected
6.16.0-rc5-syzkaller-00159-g47c84997c686-dirty #0 Not tainted
------------------------------------------------------
syz-executor/7288 is trying to acquire lock:
ffff8881074e1040 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}, at: __flush_work+0xd2/0xbc0

but task is already holding lock:
ffff8881074e1338 (&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+0x182/0xe80
       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_unregister_dev+0x21a/0x510
       vhci_release+0x80/0xd0
       __fput+0x44c/0xa70
       task_work_run+0x1d4/0x260
       do_exit+0x6b5/0x22e0
       do_group_exit+0x21c/0x2d0
       __x64_sys_exit_group+0x3f/0x40
       x64_sys_call+0x21ba/0x21c0
       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 ***

5 locks held by syz-executor/7288:
 #0: ffff88803ab0cdc0 (&hdev->req_lock){+.+.}-{4:4}, at: hci_unregister_dev+0x212/0x510
 #1: ffff88803ab0c0b8 (&hdev->lock){+.+.}-{4:4}, at: hci_dev_close_sync+0x66a/0x1330
 #2: ffffffff8f685a88 (hci_cb_list_lock){+.+.}-{4:4}, at: hci_conn_hash_flush+0xa1/0x230
 #3: ffff8881074e1338 (&conn->lock#2){+.+.}-{4:4}, at: l2cap_conn_del+0x70/0x680
 #4: ffffffff8e13f160 (rcu_read_lock){....}-{1:3}, at: __flush_work+0xd2/0xbc0

stack backtrace:
CPU: 1 UID: 0 PID: 7288 Comm: syz-executor Not tainted 6.16.0-rc5-syzkaller-00159-g47c84997c686-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_unregister_dev+0x21a/0x510
 vhci_release+0x80/0xd0
 __fput+0x44c/0xa70
 task_work_run+0x1d4/0x260
 do_exit+0x6b5/0x22e0
 do_group_exit+0x21c/0x2d0
 __x64_sys_exit_group+0x3f/0x40
 x64_sys_call+0x21ba/0x21c0
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f4e5ed8e929
Code: Unable to access opcode bytes at 0x7f4e5ed8e8ff.
RSP: 002b:00007ffe1f798c48 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f4e5ed8e929
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000043
RBP: 00007f4e5edee8f0 R08: 00007ffe1f7969e7 R09: 0000000000000003
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 0000000000000003 R14: 00000000ffffffff R15: 00007ffe1f798e00
 </TASK>
