Bluetooth: hci4: unexpected cc 0x1001 length: 249 > 9
Bluetooth: hci4: unexpected cc 0x0c23 length: 249 > 4
Bluetooth: hci4: unexpected cc 0x0c38 length: 249 > 2
device: 'hci4:200': device_add
kobject: 'hci4:200' (ffff888023f38cf0): kobject_add_internal: parent: 'hci4', set: 'devices'
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G             L     
------------------------------------------------------
kworker/u9:2/5638 is trying to acquire lock:
ffff88801d28ca10 (&root->kernfs_iattr_rwsem){++++}-{4:4}, at: kernfs_link_sibling+0x539/0x6b0 fs/kernfs/dir.c:413

but task is already holding lock:
ffff88801d28c980 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_add_one+0x41/0x510 fs/kernfs/dir.c:833

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #9 (&root->kernfs_rwsem){++++}-{4:4}:
       down_write+0x91/0x200 kernel/locking/rwsem.c:1631
       kernfs_add_one+0x41/0x510 fs/kernfs/dir.c:833
       kernfs_create_dir_ns+0x18c/0x220 fs/kernfs/dir.c:1143
       internal_create_group+0x440/0x1180 fs/sysfs/group.c:176
       cpuhp_invoke_callback+0x434/0x810 kernel/cpu.c:194
       cpuhp_issue_call+0x3f0/0x750 kernel/cpu.c:-1
       __cpuhp_setup_state_cpuslocked+0x3f4/0x6f0 kernel/cpu.c:2507
       __cpuhp_setup_state+0x3f/0x60 kernel/cpu.c:2536
       do_one_initcall+0x250/0x870 init/main.c:1419
       do_initcall_level+0x10a/0x1a0 init/main.c:1481
       do_initcalls+0x59/0xa0 init/main.c:1497
       kernel_init_freeable+0x29d/0x3e0 init/main.c:1732
       kernel_init+0x22/0x1d0 init/main.c:1622
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #8 (cpuhp_state_mutex){+.+.}-{4:4}:

-> #7 (cpu_hotplug_lock){++++}-{0:0}:
       percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline]
       percpu_down_read include/linux/percpu-rwsem.h:77 [inline]
       cpus_read_lock+0x3d/0x160 kernel/cpu.c:490
       static_key_slow_inc+0x12/0x30 kernel/jump_label.c:190
       nbd_genl_reconnect_sock_cb+0x69a/0xbb0 drivers/block/nbd.c:1377
       nbd_genl_foreach_sock+0x265/0x450 drivers/block/nbd.c:2152
       nbd_genl_reconfigure+0xbbb/0x1040 drivers/block/nbd.c:2477
       genl_family_rcv_msg_doit+0x233/0x340 net/netlink/genetlink.c:1114
       genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline]
       genl_rcv_msg+0x614/0x7a0 net/netlink/genetlink.c:1209
       netlink_rcv_skb+0x226/0x4a0 net/netlink/af_netlink.c:2584
       genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218
       netlink_unicast_kernel net/netlink/af_netlink.c:1335 [inline]
       netlink_unicast+0x8ef/0xa80 net/netlink/af_netlink.c:1361
       netlink_sendmsg+0x7f0/0xb20 net/netlink/af_netlink.c:1920
       sock_sendmsg_nosec+0x14e/0x190 net/socket.c:800
       __sock_sendmsg net/socket.c:818 [inline]
       ____sys_sendmsg+0x54e/0x850 net/socket.c:2715
       ___sys_sendmsg+0x2a6/0x360 net/socket.c:2769
       __sys_sendmsg net/socket.c:2801 [inline]
       __do_sys_sendmsg net/socket.c:2806 [inline]
       __se_sys_sendmsg net/socket.c:2804 [inline]
       __x64_sys_sendmsg+0x1b1/0x290 net/socket.c:2804
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #6 (&nsock->tx_lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x197/0x15a0 kernel/locking/mutex.c:821
       nbd_handle_cmd drivers/block/nbd.c:1143 [inline]
       nbd_queue_rq+0x373/0xff0 drivers/block/nbd.c:1207
       blk_mq_dispatch_rq_list+0x499/0x1990 block/blk-mq.c:2141
       __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline]
       blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline]
       __blk_mq_sched_dispatch_requests+0xd36/0x1580 block/blk-mq-sched.c:307
       blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329
       blk_mq_run_work_fn+0x167/0x2f0 block/blk-mq.c:2556
       process_one_work kernel/workqueue.c:3495 [inline]
       process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3578
       worker_thread+0xa47/0xfb0 kernel/workqueue.c:3659
       kthread+0x38b/0x480 kernel/kthread.c:436
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #5 (&cmd->lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x197/0x15a0 kernel/locking/mutex.c:821
       nbd_queue_rq+0xc1/0xff0 drivers/block/nbd.c:1199
       blk_mq_dispatch_rq_list+0x499/0x1990 block/blk-mq.c:2141
       __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline]
       blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline]
       __blk_mq_sched_dispatch_requests+0xd36/0x1580 block/blk-mq-sched.c:307
       blk_mq_sched_dispatch_requests+0xd7/0x190 block/blk-mq-sched.c:329
       blk_mq_run_work_fn+0x167/0x2f0 block/blk-mq.c:2556
       process_one_work kernel/workqueue.c:3495 [inline]
       process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3578
       worker_thread+0xa47/0xfb0 kernel/workqueue.c:3659
       kthread+0x38b/0x480 kernel/kthread.c:436
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #4 (set->srcu){.+.+}-{0:0}:
       srcu_lock_sync include/linux/srcu.h:225 [inline]
       __synchronize_srcu+0xca/0x2f0 kernel/rcu/srcutree.c:1662
       elevator_switch+0x1e8/0x7b0 block/elevator.c:576
       elevator_change+0x2fa/0x480 block/elevator.c:681
       elevator_set_default+0x375/0x440 block/elevator.c:754
       blk_register_queue+0x404/0x4f0 block/blk-sysfs.c:992
       __add_disk+0x6b8/0xdb0 block/genhd.c:531
       add_disk_fwnode+0x100/0x3a0 block/genhd.c:600
       add_disk include/linux/blkdev.h:801 [inline]
       nbd_dev_add+0x733/0xb60 drivers/block/nbd.c:2026
       nbd_init+0x168/0x1f0 drivers/block/nbd.c:2743
       do_one_initcall+0x250/0x870 init/main.c:1419
       do_initcall_level+0x10a/0x1a0 init/main.c:1481
       do_initcalls+0x59/0xa0 init/main.c:1497
       kernel_init_freeable+0x29d/0x3e0 init/main.c:1732
       kernel_init+0x22/0x1d0 init/main.c:1622
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #3 (&q->elevator_lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x197/0x15a0 kernel/locking/mutex.c:821
       elevator_change+0x1af/0x480 block/elevator.c:679
       elv_iosched_store+0x504/0x630 block/elevator.c:826
       queue_attr_store+0x207/0x2b0 block/blk-sysfs.c:906
       kernfs_fop_write_iter+0x3a4/0x540 fs/kernfs/file.c:345
       new_sync_write fs/read_write.c:595 [inline]
       vfs_write+0x612/0xba0 fs/read_write.c:687
       ksys_write+0x150/0x270 fs/read_write.c:1036
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&q->q_usage_counter(io)#17){++++}-{0:0}:
       blk_alloc_queue+0x544/0x690 block/blk-core.c:505
       blk_mq_alloc_queue block/blk-mq.c:4460 [inline]
       __blk_mq_alloc_disk+0x194/0x390 block/blk-mq.c:4507
       loop_add+0x480/0xb40 drivers/block/loop.c:1971
       loop_init+0xd7/0x160 drivers/block/loop.c:2210
       do_one_initcall+0x250/0x870 init/main.c:1419
       do_initcall_level+0x10a/0x1a0 init/main.c:1481
       do_initcalls+0x59/0xa0 init/main.c:1497
       kernel_init_freeable+0x29d/0x3e0 init/main.c:1732
       kernel_init+0x22/0x1d0 init/main.c:1622
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #1 (fs_reclaim){+.+.}-{0:0}:
       __fs_reclaim_acquire mm/page_alloc.c:4363 [inline]
       fs_reclaim_acquire+0x71/0x100 mm/page_alloc.c:4377
       might_alloc include/linux/sched/mm.h:316 [inline]
       slab_pre_alloc_hook mm/slub.c:4673 [inline]
       slab_alloc_node mm/slub.c:5011 [inline]
       kmem_cache_alloc_noprof+0x5f/0x600 mm/slub.c:5047
       __kernfs_iattrs+0xdd/0x380 fs/kernfs/inode.c:36
       kernfs_iattrs fs/kernfs/inode.c:60 [inline]
       __kernfs_setattr fs/kernfs/inode.c:73 [inline]
       kernfs_iop_setattr+0xe6/0x3f0 fs/kernfs/inode.c:127
       notify_change+0xbba/0xea0 fs/attr.c:556
       do_truncate+0x1c2/0x250 fs/open.c:68
       handle_truncate fs/namei.c:4306 [inline]
       do_open fs/namei.c:4855 [inline]
       path_openat+0x18a6/0x20f0 fs/namei.c:5016
       do_file_open+0x23e/0x4a0 fs/namei.c:5045
       do_sys_openat2+0x115/0x200 fs/open.c:1442
       do_sys_open fs/open.c:1448 [inline]
       __do_sys_openat fs/open.c:1788 [inline]
       __se_sys_openat fs/open.c:1783 [inline]
       __x64_sys_openat+0x138/0x170 fs/open.c:1783
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&root->kernfs_iattr_rwsem){++++}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3209 [inline]
       check_prevs_add kernel/locking/lockdep.c:3328 [inline]
       validate_chain kernel/locking/lockdep.c:3952 [inline]
       __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288
       lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942
       down_write+0x91/0x200 kernel/locking/rwsem.c:1631
       kernfs_link_sibling+0x539/0x6b0 fs/kernfs/dir.c:413
       kernfs_add_one+0x30a/0x510 fs/kernfs/dir.c:852
       kernfs_create_dir_ns+0x18c/0x220 fs/kernfs/dir.c:1143
       sysfs_create_dir_ns+0x12f/0x2a0 fs/sysfs/dir.c:59
       create_dir lib/kobject.c:73 [inline]
       kobject_add_internal+0x622/0xcd0 lib/kobject.c:240
       kobject_add_varg lib/kobject.c:374 [inline]
       kobject_add+0x163/0x240 lib/kobject.c:426
       device_add+0x3fa/0xb80 drivers/base/core.c:3701
       hci_conn_add_sysfs+0xd5/0x210 net/bluetooth/hci_sysfs.c:61
       hci_conn_complete_evt+0x8a8/0x1350 net/bluetooth/hci_event.c:3319
       hci_event_func net/bluetooth/hci_event.c:8082 [inline]
       hci_event_packet+0x6cd/0xf10 net/bluetooth/hci_event.c:8133
       hci_rx_work+0x2b4/0x1110 net/bluetooth/hci_core.c:4238
       process_one_work kernel/workqueue.c:3495 [inline]
       process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3578
       worker_thread+0xa47/0xfb0 kernel/workqueue.c:3659
       kthread+0x38b/0x480 kernel/kthread.c:436
       ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

other info that might help us debug this:

Chain exists of:
  &root->kernfs_iattr_rwsem --> cpuhp_state_mutex --> &root->kernfs_rwsem

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&root->kernfs_rwsem);
                               lock(cpuhp_state_mutex);
                               lock(&root->kernfs_rwsem);
  lock(&root->kernfs_iattr_rwsem);

 *** DEADLOCK ***

locks held by kworker/u9:2/5638: 4, last CPU#1:
 #0: ffff888057702948 ((wq_completion)hci4#2){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #0: ffff888057702948 ((wq_completion)hci4#2){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #0: ffff888057702948 ((wq_completion)hci4#2){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3460 [inline]
 #0: ffff888057702948 ((wq_completion)hci4#2){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3578
 #1: ffffc90004297c40 ((work_completion)(&hdev->rx_work)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #1: ffffc90004297c40 ((work_completion)(&hdev->rx_work)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #1: ffffc90004297c40 ((work_completion)(&hdev->rx_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3460 [inline]
 #1: ffffc90004297c40 ((work_completion)(&hdev->rx_work)){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3578
 #2: ffff888064d940b8 (&hdev->lock){+.+.}-{4:4}, at: hci_conn_complete_evt+0xba/0x1350 net/bluetooth/hci_event.c:3236
 #3: ffff88801d28c980 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_add_one+0x41/0x510 fs/kernfs/dir.c:833

stack backtrace:
CPU: 1 UID: 0 PID: 5638 Comm: kworker/u9:2 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
Workqueue: hci4 hci_rx_work
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2087
 check_noncircular+0x12f/0x150 kernel/locking/lockdep.c:2219
 check_prev_add kernel/locking/lockdep.c:3209 [inline]
 check_prevs_add kernel/locking/lockdep.c:3328 [inline]
 validate_chain kernel/locking/lockdep.c:3952 [inline]
 __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288
 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942
 down_write+0x91/0x200 kernel/locking/rwsem.c:1631
 kernfs_link_sibling+0x539/0x6b0 fs/kernfs/dir.c:413
 kernfs_add_one+0x30a/0x510 fs/kernfs/dir.c:852
 kernfs_create_dir_ns+0x18c/0x220 fs/kernfs/dir.c:1143
 sysfs_create_dir_ns+0x12f/0x2a0 fs/sysfs/dir.c:59
 create_dir lib/kobject.c:73 [inline]
 kobject_add_internal+0x622/0xcd0 lib/kobject.c:240
 kobject_add_varg lib/kobject.c:374 [inline]
 kobject_add+0x163/0x240 lib/kobject.c:426
 device_add+0x3fa/0xb80 drivers/base/core.c:3701
 hci_conn_add_sysfs+0xd5/0x210 net/bluetooth/hci_sysfs.c:61
 hci_conn_complete_evt+0x8a8/0x1350 net/bluetooth/hci_event.c:3319
 hci_event_func net/bluetooth/hci_event.c:8082 [inline]
 hci_event_packet+0x6cd/0xf10 net/bluetooth/hci_event.c:8133
 hci_rx_work+0x2b4/0x1110 net/bluetooth/hci_core.c:4238
 process_one_work kernel/workqueue.c:3495 [inline]
 process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3578
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3659
 kthread+0x38b/0x480 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
PM: Adding info for No Bus:hci4:200
kobject: 'hci4:200' (ffff888023f38cf0): kobject_uevent_env
kobject: 'hci4:200' (ffff888023f38cf0): fill_kobj_path: path = '/devices/virtual/bluetooth/hci4/hci4:200'
hci4 opcode 0x041b plen 2
hci4: skb len 5
hci4 opcode 0x040f plen 4
hci4: skb len 7
kcov: kcov_move_area: ffffc9001e848000 1048576 <= ffffc9001a03b000 1048575
kcov: kcov_remote_start: handle = 3, context: task
kcov: kcov_start: t = ffff88807bcb3e80, size = 1048576, area = ffffc9001a03b000
hci4 Event packet
hci4: event 0x0b
hci4: status 0x00
hci4 opcode 0x0419 plen 10
hci4: skb len 13
hcon ffff888023f38000 bdaddr 10:aa:aa:aa:aa:aa status 0
hci4 hcon ffff888023f38000
hcon ffff888023f38000 conn ffff888037e23800 hchan ffff88807d96d600
conn ffff888037e23800
conn ffff888037e23800, code 0x0a, ident 0x01, len 2
code 0x0a
hci4 chan ffff88807d96d600 flags 0x0002
hci4 nonfrag skb ffff888033d7c3c0 len 14
hci4: chan ffff88807d96d600 queued 1
hcon ffff888023f38000 orig refcnt 1
kcov: kcov_move_area: ffffc9001e848000 1048576 <= ffffc9001a03b000 7781
kcov: kcov_remote_start: handle = 3, context: task
kcov: kcov_start: t = ffff88807bcb3e80, size = 1048576, area = ffffc9001a03b000
hci4 Event packet
hci4: event 0x3e
hci4: subevent 0x01
hci4: status 0x00
hci4: dst 11:aa:aa:aa:aa:aa
hci4: dst 11:aa:aa:aa:aa:aa handle 0x0f00
hci4 orig refcnt 10
hci4: conn ffff8880372a8000
hci4: hcon ffff8880372a8000 handle 0x00c9
channel 3 len 19
hci4: conn ffff8880372a8000
device: 'hci4:201': device_add
kobject: 'hci4:201' (ffff8880372a8cf0): kobject_add_internal: parent: 'hci4', set: 'devices'
PM: Adding info for No Bus:hci4:201
kobject: 'hci4:201' (ffff8880372a8cf0): kobject_uevent_env
kobject: 'hci4:201' (ffff8880372a8cf0): fill_kobj_path: path = '/devices/virtual/bluetooth/hci4/hci4:201'
hcon ffff8880372a8000 bdaddr 11:aa:aa:aa:aa:aa status 0
hci4 hcon ffff8880372a8000
hcon ffff8880372a8000 conn ffff888056905000 hchan ffff88802b2ff400
conn ffff888056905000
hci4 conn ffff888056905000
conn ffff888056905000, code 0x12, ident 0x01, len 8
code 0x12
hci4 chan ffff88802b2ff400 flags 0x0000
hci4 nonfrag skb ffff888052e40dc0 len 20
hci4: chan ffff88802b2ff400 queued 1
kcov: kcov_move_area: ffffc9001e848000 1048576 <= ffffc9001a03b000 16847
hci5 cmd_cnt 1 cmd queued 1
hci5: skb ffff88805e276c80
hci5 type 1 len 6
hci4: 
hci4: entry ffff888066d4bb00
hci4: entry ffff888066d4b480
hci4 cmd_cnt 1 cmd queued 4
hci4: skb ffff888064d5d780
hci4 type 1 len 10
hci4 acl 4 sco 0 le 0 iso 0
hci4: type 0
hci4: type 2
hci4
hci4
hci4
hci4
hci4
chan ffff88807d96d600 quote 4
chan ffff88807d96d600 skb ffff888033d7c3c0 len 14 priority 7
hcon ffff888023f38000 mode 0
hci4 type 2 len 14
hci4: type 0
hci4: type 2
hci4
hci4
hci4
hci4
chan ffff88802b2ff400 quote 3
chan ffff88802b2ff400 skb ffff888052e40dc0 len 20 priority 7
hci4 type 2 len 20
hci4: type 0
hci4: type 2
hci4
hci4