======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G             L     
------------------------------------------------------
syz.5.3522/15377 is trying to acquire lock:
ffff8880b8824358 (tasklet_sync_callback.cb_lock){+...}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:44 [inline]
ffff8880b8824358 (tasklet_sync_callback.cb_lock){+...}-{3:3}, at: tasklet_lock_callback kernel/softirq.c:864 [inline]
ffff8880b8824358 (tasklet_sync_callback.cb_lock){+...}-{3:3}, at: tasklet_action_common+0xb6/0x540 kernel/softirq.c:914

but task is already holding lock:
ffff888038aaa270 (&dev->event_lock#2){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:44 [inline]
ffff888038aaa270 (&dev->event_lock#2){+.+.}-{3:3}, at: class_spinlock_irqsave_constructor include/linux/spinlock.h:585 [inline]
ffff888038aaa270 (&dev->event_lock#2){+.+.}-{3:3}, at: input_inject_event+0xa5/0x330 drivers/input/input.c:419

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&dev->event_lock#2){+.+.}-{3:3}:
       rt_spin_lock+0x88/0x3e0 kernel/locking/spinlock_rt.c:56
       spin_lock include/linux/spinlock_rt.h:44 [inline]
       class_spinlock_irqsave_constructor include/linux/spinlock.h:585 [inline]
       input_inject_event+0xa5/0x330 drivers/input/input.c:419
       led_trigger_event+0x13b/0x220 drivers/leds/led-triggers.c:420
       kbd_propagate_led_state drivers/tty/vt/keyboard.c:1065 [inline]
       kbd_bh+0x1ec/0x300 drivers/tty/vt/keyboard.c:1244
       tasklet_action_common+0x2bf/0x540 kernel/softirq.c:925
       handle_softirqs+0x1df/0x650 kernel/softirq.c:622
       __do_softirq kernel/softirq.c:656 [inline]
       __local_bh_enable_ip+0x171/0x2c0 kernel/softirq.c:302
       lock_sock include/net/sock.h:1700 [inline]
       l2cap_sock_connect+0xfe/0x7d0 net/bluetooth/l2cap_sock.c:192
       __sys_connect_file net/socket.c:2089 [inline]
       __sys_connect+0x323/0x450 net/socket.c:2108
       __do_sys_connect net/socket.c:2114 [inline]
       __se_sys_connect net/socket.c:2111 [inline]
       __x64_sys_connect+0x7a/0x90 net/socket.c:2111
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (tasklet_sync_callback.cb_lock){+...}-{3:3}:
       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+0x15a6/0x2cf0 kernel/locking/lockdep.c:5237
       lock_acquire+0x107/0x340 kernel/locking/lockdep.c:5868
       rt_spin_lock+0x88/0x3e0 kernel/locking/spinlock_rt.c:56
       spin_lock include/linux/spinlock_rt.h:44 [inline]
       tasklet_lock_callback kernel/softirq.c:864 [inline]
       tasklet_action_common+0xb6/0x540 kernel/softirq.c:914
       handle_softirqs+0x1df/0x650 kernel/softirq.c:622
       __do_softirq kernel/softirq.c:656 [inline]
       __local_bh_enable_ip+0x171/0x2c0 kernel/softirq.c:302
       local_bh_enable include/linux/bottom_half.h:33 [inline]
       __alloc_skb+0x1bc/0x3a0 net/core/skbuff.c:674
       alloc_skb include/linux/skbuff.h:1383 [inline]
       hidp_send_message+0xb5/0x230 net/bluetooth/hidp/core.c:111
       hidp_send_intr_message net/bluetooth/hidp/core.c:143 [inline]
       hidp_input_event+0x290/0x370 net/bluetooth/hidp/core.c:175
       input_event_dispose+0x80/0x6b0 drivers/input/input.c:322
       input_inject_event+0x1d8/0x330 drivers/input/input.c:424
       kbd_led_trigger_activate+0xbc/0x100 drivers/tty/vt/keyboard.c:1021
       led_trigger_set+0x533/0x950 drivers/leds/led-triggers.c:220
       led_match_default_trigger drivers/leds/led-triggers.c:277 [inline]
       led_trigger_set_default+0x266/0x2a0 drivers/leds/led-triggers.c:300
       led_classdev_register_ext+0x73d/0x960 drivers/leds/led-class.c:578
       led_classdev_register include/linux/leds.h:274 [inline]
       input_leds_connect+0x517/0x790 drivers/input/input-leds.c:145
       input_attach_handler drivers/input/input.c:994 [inline]
       input_register_device+0xd00/0x1170 drivers/input/input.c:2378
       hidp_session_dev_add net/bluetooth/hidp/core.c:861 [inline]
       hidp_session_probe+0x1a8/0x8a0 net/bluetooth/hidp/core.c:1116
       l2cap_register_user+0xf4/0x200 net/bluetooth/l2cap_core.c:1712
       hidp_connection_add+0x158b/0x1a20 net/bluetooth/hidp/core.c:1378
       do_hidp_sock_ioctl net/bluetooth/hidp/sock.c:81 [inline]
       hidp_sock_ioctl+0x3a8/0x5c0 net/bluetooth/hidp/sock.c:128
       sock_do_ioctl+0xdc/0x300 net/socket.c:1254
       sock_ioctl+0x579/0x790 net/socket.c:1375
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl+0xff/0x170 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xec/0xf80 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(&dev->event_lock#2);
                               lock(tasklet_sync_callback.cb_lock);
                               lock(&dev->event_lock#2);
  lock(tasklet_sync_callback.cb_lock);

 *** DEADLOCK ***

10 locks held by syz.5.3522/15377:
 #0: ffff88805e1140b0 (&hdev->lock){+.+.}-{4:4}, at: l2cap_register_user+0x67/0x200 net/bluetooth/l2cap_core.c:1699
 #1: ffffffff8ea40100 (hidp_session_sem){++++}-{4:4}, at: hidp_session_probe+0x99/0x8a0 net/bluetooth/hidp/core.c:1106
 #2: ffffffff8e326af8 (input_mutex){+.+.}-{4:4}, at: class_mutex_intr_constructor include/linux/mutex.h:255 [inline]
 #2: ffffffff8e326af8 (input_mutex){+.+.}-{4:4}, at: input_register_device+0xa76/0x1170 drivers/input/input.c:2374
 #3: ffff8880383885a0 (&led_cdev->led_access){+.+.}-{4:4}, at: led_classdev_register_ext+0x43d/0x960 drivers/leds/led-class.c:536
 #4: ffffffff8dd126c0 (triggers_list_lock){++++}-{4:4}, at: led_trigger_set_default+0x77/0x2a0 drivers/leds/led-triggers.c:297
 #5: ffff8880383884c8 (&led_cdev->trigger_lock){+.+.}-{4:4}, at: led_trigger_set_default+0x87/0x2a0 drivers/leds/led-triggers.c:298
 #6: ffff888038aaa270 (&dev->event_lock#2){+.+.}-{3:3}, at: spin_lock include/linux/spinlock_rt.h:44 [inline]
 #6: ffff888038aaa270 (&dev->event_lock#2){+.+.}-{3:3}, at: class_spinlock_irqsave_constructor include/linux/spinlock.h:585 [inline]
 #6: ffff888038aaa270 (&dev->event_lock#2){+.+.}-{3:3}, at: input_inject_event+0xa5/0x330 drivers/input/input.c:419
 #7: ffffffff8d5ae940 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #7: ffffffff8d5ae940 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline]
 #7: ffffffff8d5ae940 (rcu_read_lock){....}-{1:3}, at: __rt_spin_lock kernel/locking/spinlock_rt.c:50 [inline]
 #7: ffffffff8d5ae940 (rcu_read_lock){....}-{1:3}, at: rt_spin_lock+0x1c1/0x3e0 kernel/locking/spinlock_rt.c:57
 #8: ffffffff8d5ae940 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #8: ffffffff8d5ae940 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline]
 #8: ffffffff8d5ae940 (rcu_read_lock){....}-{1:3}, at: class_rcu_constructor include/linux/rcupdate.h:1195 [inline]
 #8: ffffffff8d5ae940 (rcu_read_lock){....}-{1:3}, at: input_inject_event+0xb1/0x330 drivers/input/input.c:420
 #9: ffffffff8d5ae940 (rcu_read_lock){....}-{1:3}, at: __local_bh_disable_ip+0x3c/0x420 kernel/softirq.c:163

stack backtrace:
CPU: 0 UID: 0 PID: 15377 Comm: syz.5.3522 Tainted: G             L      syzkaller #0 PREEMPT_{RT,(full)} 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2043
 check_noncircular+0x12e/0x150 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+0x15a6/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0x107/0x340 kernel/locking/lockdep.c:5868
 rt_spin_lock+0x88/0x3e0 kernel/locking/spinlock_rt.c:56
 spin_lock include/linux/spinlock_rt.h:44 [inline]
 tasklet_lock_callback kernel/softirq.c:864 [inline]
 tasklet_action_common+0xb6/0x540 kernel/softirq.c:914
 handle_softirqs+0x1df/0x650 kernel/softirq.c:622
 __do_softirq kernel/softirq.c:656 [inline]
 __local_bh_enable_ip+0x171/0x2c0 kernel/softirq.c:302
 local_bh_enable include/linux/bottom_half.h:33 [inline]
 __alloc_skb+0x1bc/0x3a0 net/core/skbuff.c:674
 alloc_skb include/linux/skbuff.h:1383 [inline]
 hidp_send_message+0xb5/0x230 net/bluetooth/hidp/core.c:111
 hidp_send_intr_message net/bluetooth/hidp/core.c:143 [inline]
 hidp_input_event+0x290/0x370 net/bluetooth/hidp/core.c:175
 input_event_dispose+0x80/0x6b0 drivers/input/input.c:322
 input_inject_event+0x1d8/0x330 drivers/input/input.c:424
 kbd_led_trigger_activate+0xbc/0x100 drivers/tty/vt/keyboard.c:1021
 led_trigger_set+0x533/0x950 drivers/leds/led-triggers.c:220
 led_match_default_trigger drivers/leds/led-triggers.c:277 [inline]
 led_trigger_set_default+0x266/0x2a0 drivers/leds/led-triggers.c:300
 led_classdev_register_ext+0x73d/0x960 drivers/leds/led-class.c:578
 led_classdev_register include/linux/leds.h:274 [inline]
 input_leds_connect+0x517/0x790 drivers/input/input-leds.c:145
 input_attach_handler drivers/input/input.c:994 [inline]
 input_register_device+0xd00/0x1170 drivers/input/input.c:2378
 hidp_session_dev_add net/bluetooth/hidp/core.c:861 [inline]
 hidp_session_probe+0x1a8/0x8a0 net/bluetooth/hidp/core.c:1116
 l2cap_register_user+0xf4/0x200 net/bluetooth/l2cap_core.c:1712
 hidp_connection_add+0x158b/0x1a20 net/bluetooth/hidp/core.c:1378
 do_hidp_sock_ioctl net/bluetooth/hidp/sock.c:81 [inline]
 hidp_sock_ioctl+0x3a8/0x5c0 net/bluetooth/hidp/sock.c:128
 sock_do_ioctl+0xdc/0x300 net/socket.c:1254
 sock_ioctl+0x579/0x790 net/socket.c:1375
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xff/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f76daedf749
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:00007f76d9125038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f76db136090 RCX: 00007f76daedf749
RDX: 00002000000000c0 RSI: 00000000400448c8 RDI: 0000000000000008
RBP: 00007f76daf63f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f76db136128 R14: 00007f76db136090 R15: 00007ffd7a813ec8
 </TASK>
BUG: workqueue leaked atomic, lock or RCU: ksoftirqd/0[15]
     preempt=0x00000000 lock=4->0 RCU=2->2 workfn=usb_giveback_urb_bh
INFO: lockdep is turned off.
CPU: 0 UID: 0 PID: 15 Comm: ksoftirqd/0 Tainted: G             L      syzkaller #0 PREEMPT_{RT,(full)} 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 process_one_work kernel/workqueue.c:3278 [inline]
 process_scheduled_works+0x11ab/0x1770 kernel/workqueue.c:3340
 bh_worker+0x2ca/0x630 kernel/workqueue.c:3611
 tasklet_hi_action+0xf/0x70 kernel/softirq.c:958
 handle_softirqs+0x1df/0x650 kernel/softirq.c:622
 run_ksoftirqd+0x52/0x190 kernel/softirq.c:1063
 smpboot_thread_fn+0x542/0xa60 kernel/smpboot.c:160
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>