======================================================
WARNING: possible circular locking dependency detected
6.16.0-syzkaller-08685-g260f6f4fda93 #0 Not tainted
------------------------------------------------------
syz.7.3352/18481 is trying to acquire lock:
ffff8880351cf840 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}
, at: touch_work_lockdep_map kernel/workqueue.c:3924 [inline]
, at: start_flush_work kernel/workqueue.c:4178 [inline]
, at: __flush_work+0x4d0/0xcc0 kernel/workqueue.c:4210

but task is already holding lock:
ffff8880351cfb38 (&conn->lock#2){+.+.}-{4:4}, at: l2cap_conn_del+0x80/0x730 net/bluetooth/l2cap_core.c:1762

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&conn->lock#2){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:598 [inline]
       __mutex_lock+0x191/0x1070 kernel/locking/mutex.c:760
       l2cap_info_timeout+0x79/0xa0 net/bluetooth/l2cap_core.c:1668
       process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3238
       process_scheduled_works kernel/workqueue.c:3321 [inline]
       worker_thread+0x6c8/0xf10 kernel/workqueue.c:3402
       kthread+0x3c5/0x780 kernel/kthread.c:464
       ret_from_fork+0x5d4/0x6f0 arch/x86/kernel/process.c:148
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #0 ((work_completion)(&(&conn->info_timer)->work)){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3165 [inline]
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5237
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5825
       touch_work_lockdep_map kernel/workqueue.c:3924 [inline]
       start_flush_work kernel/workqueue.c:4178 [inline]
       __flush_work+0x4e4/0xcc0 kernel/workqueue.c:4210
       __cancel_work_sync+0x10c/0x130 kernel/workqueue.c:4366
       l2cap_conn_del+0x5af/0x730 net/bluetooth/l2cap_core.c:1796
       l2cap_disconn_cfm net/bluetooth/l2cap_core.c:7325 [inline]
       l2cap_disconn_cfm+0x96/0xd0 net/bluetooth/l2cap_core.c:7318
       hci_disconn_cfm include/net/bluetooth/hci_core.h:2065 [inline]
       hci_conn_hash_flush+0x10e/0x260 net/bluetooth/hci_conn.c:2564
       hci_dev_close_sync+0x602/0x11d0 net/bluetooth/hci_sync.c:5294
       hci_dev_do_close+0x2e/0x90 net/bluetooth/hci_core.c:501
       hci_dev_close+0x185/0x1e0 net/bluetooth/hci_core.c:526
       hci_sock_ioctl+0x2b3/0x7d0 net/bluetooth/hci_sock.c:1135
       sock_do_ioctl+0x118/0x280 net/socket.c:1238
       sock_ioctl+0x227/0x6b0 net/socket.c:1359
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:598 [inline]
       __se_sys_ioctl fs/ioctl.c:584 [inline]
       __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:584
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
       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.7.3352/18481:
 #0: ffff88802bb54dc0 (&hdev->req_lock){+.+.}-{4:4}, at: hci_dev_do_close+0x26/0x90 net/bluetooth/hci_core.c:499
 #1: ffff88802bb540b8 (&hdev->lock){+.+.}-{4:4}, at: hci_dev_close_sync+0x3ae/0x11d0 net/bluetooth/hci_sync.c:5282
 #2: ffffffff905b4c68 (hci_cb_list_lock){+.+.}-{4:4}, at: hci_disconn_cfm include/net/bluetooth/hci_core.h:2062 [inline]
 #2: ffffffff905b4c68 (hci_cb_list_lock){+.+.}-{4:4}, at: hci_conn_hash_flush+0xbb/0x260 net/bluetooth/hci_conn.c:2564
 #3: ffff8880351cfb38 (&conn->lock#2){+.+.}-{4:4}, at: l2cap_conn_del+0x80/0x730 net/bluetooth/l2cap_core.c:1762
 #4: ffffffff8e5c1060 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #4: ffffffff8e5c1060 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
 #4: ffffffff8e5c1060 (rcu_read_lock){....}-{1:3}, at: start_flush_work kernel/workqueue.c:4152 [inline]
 #4: ffffffff8e5c1060 (rcu_read_lock){....}-{1:3}, at: __flush_work+0xfb/0xcc0 kernel/workqueue.c:4210

stack backtrace:
CPU: 0 UID: 0 PID: 18481 Comm: syz.7.3352 Not tainted 6.16.0-syzkaller-08685-g260f6f4fda93 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_circular_bug+0x275/0x350 kernel/locking/lockdep.c:2043
 check_noncircular+0x14c/0x170 kernel/locking/lockdep.c:2175
 check_prev_add kernel/locking/lockdep.c:3165 [inline]
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5237
 lock_acquire kernel/locking/lockdep.c:5868 [inline]
 lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5825
 touch_work_lockdep_map kernel/workqueue.c:3924 [inline]
 start_flush_work kernel/workqueue.c:4178 [inline]
 __flush_work+0x4e4/0xcc0 kernel/workqueue.c:4210
 __cancel_work_sync+0x10c/0x130 kernel/workqueue.c:4366
 l2cap_conn_del+0x5af/0x730 net/bluetooth/l2cap_core.c:1796
 l2cap_disconn_cfm net/bluetooth/l2cap_core.c:7325 [inline]
 l2cap_disconn_cfm+0x96/0xd0 net/bluetooth/l2cap_core.c:7318
 hci_disconn_cfm include/net/bluetooth/hci_core.h:2065 [inline]
 hci_conn_hash_flush+0x10e/0x260 net/bluetooth/hci_conn.c:2564
 hci_dev_close_sync+0x602/0x11d0 net/bluetooth/hci_sync.c:5294
 hci_dev_do_close+0x2e/0x90 net/bluetooth/hci_core.c:501
 hci_dev_close+0x185/0x1e0 net/bluetooth/hci_core.c:526
 hci_sock_ioctl+0x2b3/0x7d0 net/bluetooth/hci_sock.c:1135
 sock_do_ioctl+0x118/0x280 net/socket.c:1238
 sock_ioctl+0x227/0x6b0 net/socket.c:1359
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:598 [inline]
 __se_sys_ioctl fs/ioctl.c:584 [inline]
 __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:584
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5562f8eb69
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:00007f5563ed2038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f55631b5fa0 RCX: 00007f5562f8eb69
RDX: 0000000000000000 RSI: 00000000400448ca RDI: 0000000000000009
RBP: 00007f5563011df1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f55631b5fa0 R15: 00007ffc7dfa1b28
 </TASK>