syzbot

======================================================
WARNING: possible circular locking dependency detected
5.15.189-syzkaller #0 Not tainted
------------------------------------------------------
syz.0.17/4274 is trying to acquire lock:
ffff0000d0a34c28
 ((work_completion)(&hdev->bg_scan_update)
){+.+.}-{0:0}
, at: __flush_work+0xcc/0x1bc kernel/workqueue.c:3087

but task is already holding lock:
ffff80001651bc28 (rfkill_global_mutex
){+.+.}-{3:3}
, at: rfkill_fop_write+0x238/0x5cc net/rfkill/core.c:1266

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 (rfkill_global_mutex){+.+.}-{3:3}:
       __mutex_lock_common+0x194/0x1edc kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0xac/0x11c kernel/locking/mutex.c:743
       rfkill_register+0x44/0x77c net/rfkill/core.c:1045
       hci_register_dev+0x3d8/0x854 net/bluetooth/hci_core.c:3960
       __vhci_create_device drivers/bluetooth/hci_vhci.c:129 [inline]
       vhci_create_device+0x2bc/0x564 drivers/bluetooth/hci_vhci.c:153
       vhci_get_user drivers/bluetooth/hci_vhci.c:210 [inline]
       vhci_write+0x30c/0x3ac drivers/bluetooth/hci_vhci.c:290
       call_write_iter include/linux/fs.h:2172 [inline]
       new_sync_write fs/read_write.c:507 [inline]
       vfs_write+0x7c8/0xa2c fs/read_write.c:594
       ksys_write+0x120/0x210 fs/read_write.c:647
       __do_sys_write fs/read_write.c:659 [inline]
       __se_sys_write fs/read_write.c:656 [inline]
       __arm64_sys_write+0x7c/0x90 fs/read_write.c:656
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
       el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
       el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

-> #3 (&data->open_mutex){+.+.}-{3:3}:
       __mutex_lock_common+0x194/0x1edc kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0xac/0x11c kernel/locking/mutex.c:743
       vhci_send_frame+0x88/0x118 drivers/bluetooth/hci_vhci.c:71
       hci_send_frame+0x194/0x2f0 net/bluetooth/hci_core.c:4256
       hci_sched_acl_pkt net/bluetooth/hci_core.c:4781 [inline]
       hci_sched_acl net/bluetooth/hci_core.c:4866 [inline]
       hci_tx_work+0x7e4/0x1394 net/bluetooth/hci_core.c:4932
       process_one_work+0x79c/0x1140 kernel/workqueue.c:2310
       worker_thread+0x8f4/0x101c kernel/workqueue.c:2457
       kthread+0x374/0x454 kernel/kthread.c:334
       ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:855

-> #2 (
(work_completion)(&hdev->tx_work)){+.+.}-{0:0}:
       __flush_work+0xf4/0x1bc kernel/workqueue.c:3090
       flush_work+0x24/0x38 kernel/workqueue.c:3115
       hci_dev_do_close+0x164/0x105c net/bluetooth/hci_core.c:1756
       hci_unregister_dev+0x23c/0x4c0 net/bluetooth/hci_core.c:4040
       vhci_release+0x74/0xc4 drivers/bluetooth/hci_vhci.c:345
       __fput+0x1c0/0x7f8 fs/file_table.c:311
       ____fput+0x20/0x30 fs/file_table.c:339
       task_work_run+0x12c/0x1e0 kernel/task_work.c:188
       exit_task_work include/linux/task_work.h:33 [inline]
       do_exit+0x684/0x1f58 kernel/exit.c:883
       do_group_exit+0x100/0x268 kernel/exit.c:997
       get_signal+0x73c/0x1340 kernel/signal.c:2900
       do_signal arch/arm64/kernel/signal.c:893 [inline]
       do_notify_resume+0x35c/0x3128 arch/arm64/kernel/signal.c:946
       prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:133 [inline]
       exit_to_user_mode arch/arm64/kernel/entry-common.c:138 [inline]
       el0_svc+0xf0/0x1e0 arch/arm64/kernel/entry-common.c:609
       el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

-> #1 (&hdev->req_lock){+.+.}-{3:3}:
       __mutex_lock_common+0x194/0x1edc kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0xac/0x11c kernel/locking/mutex.c:743
       hci_req_sync net/bluetooth/hci_request.c:278 [inline]
       bg_scan_update+0x48/0x3d0 net/bluetooth/hci_request.c:2952
       process_one_work+0x79c/0x1140 kernel/workqueue.c:2310
       worker_thread+0x8f4/0x101c kernel/workqueue.c:2457
       kthread+0x374/0x454 kernel/kthread.c:334
       ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:855

-> #0 ((work_completion)(&hdev->bg_scan_update)){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3053 [inline]
       check_prevs_add kernel/locking/lockdep.c:3172 [inline]
       validate_chain kernel/locking/lockdep.c:3788 [inline]
       __lock_acquire+0x2928/0x651c kernel/locking/lockdep.c:5012
       lock_acquire+0x1f4/0x620 kernel/locking/lockdep.c:5623
       __flush_work+0xf4/0x1bc kernel/workqueue.c:3090
       __cancel_work_timer+0x2ec/0x448 kernel/workqueue.c:3181
       cancel_work_sync+0x24/0x38 kernel/workqueue.c:3217
       hci_request_cancel_all+0xbc/0x2d0 net/bluetooth/hci_request.c:3522
       hci_dev_do_close+0x54/0x105c net/bluetooth/hci_core.c:1736
       hci_rfkill_set_block+0xdc/0x1d0 net/bluetooth/hci_core.c:2235
       rfkill_set_block+0x18c/0x374 net/rfkill/core.c:345
       rfkill_fop_write+0x4a4/0x5cc net/rfkill/core.c:1274
       vfs_write+0x280/0xa2c fs/read_write.c:592
       ksys_write+0x120/0x210 fs/read_write.c:647
       __do_sys_write fs/read_write.c:659 [inline]
       __se_sys_write fs/read_write.c:656 [inline]
       __arm64_sys_write+0x7c/0x90 fs/read_write.c:656
       __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
       invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
       el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
       do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
       el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
       el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
       el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584

other info that might help us debug this:

Chain exists of:
  (work_completion)(&hdev->bg_scan_update) --> &data->open_mutex --> rfkill_global_mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(rfkill_global_mutex);
                               lock(&data->open_mutex);
                               lock(rfkill_global_mutex);
  lock((work_completion)(&hdev->bg_scan_update));

 *** DEADLOCK ***

1 lock held by syz.0.17/4274:
 #0: ffff80001651bc28 (rfkill_global_mutex){+.+.}-{3:3}, at: rfkill_fop_write+0x238/0x5cc net/rfkill/core.c:1266

stack backtrace:
CPU: 1 PID: 4274 Comm: syz.0.17 Not tainted 5.15.189-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/30/2025
Call trace:
 dump_backtrace+0x0/0x43c arch/arm64/kernel/stacktrace.c:152
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf8/0x160 lib/dump_stack.c:106
 dump_stack+0x1c/0x5c lib/dump_stack.c:113
 print_circular_bug+0x148/0x1b0 kernel/locking/lockdep.c:2011
 check_noncircular+0x240/0x2d4 kernel/locking/lockdep.c:2133
 check_prev_add kernel/locking/lockdep.c:3053 [inline]
 check_prevs_add kernel/locking/lockdep.c:3172 [inline]
 validate_chain kernel/locking/lockdep.c:3788 [inline]
 __lock_acquire+0x2928/0x651c kernel/locking/lockdep.c:5012
 lock_acquire+0x1f4/0x620 kernel/locking/lockdep.c:5623
 __flush_work+0xf4/0x1bc kernel/workqueue.c:3090
 __cancel_work_timer+0x2ec/0x448 kernel/workqueue.c:3181
 cancel_work_sync+0x24/0x38 kernel/workqueue.c:3217
 hci_request_cancel_all+0xbc/0x2d0 net/bluetooth/hci_request.c:3522
 hci_dev_do_close+0x54/0x105c net/bluetooth/hci_core.c:1736
 hci_rfkill_set_block+0xdc/0x1d0 net/bluetooth/hci_core.c:2235
 rfkill_set_block+0x18c/0x374 net/rfkill/core.c:345
 rfkill_fop_write+0x4a4/0x5cc net/rfkill/core.c:1274
 vfs_write+0x280/0xa2c fs/read_write.c:592
 ksys_write+0x120/0x210 fs/read_write.c:647
 __do_sys_write fs/read_write.c:659 [inline]
 __se_sys_write fs/read_write.c:656 [inline]
 __arm64_sys_write+0x7c/0x90 fs/read_write.c:656
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
 el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
 el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584