netlink: 4 bytes leftover after parsing attributes in process `syz.0.5857'.
input: Bluetooth HID Boot Protocol Device as /devices/virtual/bluetooth/hci2/hci2:200/input7
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.5857/19177 is trying to acquire lock:
ffff8881012d4210 (&root->kernfs_iattr_rwsem){++++}-{4:4}, at: kernfs_link_sibling+0x4c7/0x5a0

but task is already holding lock:
ffff8881012d4180 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_add_one+0x41/0x6f0

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #9 (&root->kernfs_rwsem){++++}-{4:4}:
       down_write+0x96/0x200
       kernfs_add_one+0x41/0x6f0
       kernfs_create_dir_ns+0x1a1/0x230
       internal_create_group+0x440/0x1180
       cpuhp_invoke_callback+0x434/0x810
       cpuhp_issue_call+0x3f0/0x750
       __cpuhp_setup_state_cpuslocked+0x3f4/0x6f0
       __cpuhp_setup_state+0x3f/0x60
       do_one_initcall+0x250/0x870
       do_initcall_level+0x10a/0x1a0
       do_initcalls+0x59/0xa0
       kernel_init_freeable+0x29d/0x3e0
       kernel_init+0x22/0x1d0
       ret_from_fork+0x514/0xb70
       ret_from_fork_asm+0x1a/0x30

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

-> #7 (cpu_hotplug_lock){++++}-{0:0}:
       cpus_read_lock+0x42/0x160
       static_key_slow_inc+0x12/0x30
       nbd_genl_reconnect_sock_cb+0x69a/0xbb0
       nbd_genl_foreach_sock+0x265/0x450
       nbd_genl_reconfigure+0xbbb/0x1040
       genl_family_rcv_msg_doit+0x233/0x340
       genl_rcv_msg+0x614/0x7a0
       netlink_rcv_skb+0x226/0x4a0
       genl_rcv+0x28/0x40
       netlink_unicast+0x7bd/0x940
       netlink_sendmsg+0x813/0xb40
       sock_sendmsg_nosec+0x14e/0x190
       ____sys_sendmsg+0x54e/0x850
       ___sys_sendmsg+0x2a5/0x360
       __x64_sys_sendmsg+0x1b1/0x290
       do_syscall_64+0x166/0x520
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #6 (&nsock->tx_lock){+.+.}-{4:4}:
       __mutex_lock+0x19d/0x1550
       nbd_queue_rq+0x373/0xff0
       blk_mq_dispatch_rq_list+0x499/0x1990
       __blk_mq_sched_dispatch_requests+0xd36/0x1580
       blk_mq_sched_dispatch_requests+0xd7/0x190
       blk_mq_run_work_fn+0x16c/0x300
       process_scheduled_works+0xc3d/0x1630
       worker_thread+0xa47/0xfb0
       kthread+0x38b/0x480
       ret_from_fork+0x514/0xb70
       ret_from_fork_asm+0x1a/0x30

-> #5 (&cmd->lock){+.+.}-{4:4}:
       __mutex_lock+0x19d/0x1550
       nbd_queue_rq+0xc1/0xff0
       blk_mq_dispatch_rq_list+0x499/0x1990
       __blk_mq_sched_dispatch_requests+0xd36/0x1580
       blk_mq_sched_dispatch_requests+0xd7/0x190
       blk_mq_run_work_fn+0x16c/0x300
       process_scheduled_works+0xc3d/0x1630
       worker_thread+0xa47/0xfb0
       kthread+0x38b/0x480
       ret_from_fork+0x514/0xb70
       ret_from_fork_asm+0x1a/0x30

-> #4 (set->srcu){.+.+}-{0:0}:
       __synchronize_srcu+0xc9/0x2f0
       elevator_switch+0x1e8/0x7b0
       elevator_change+0x2fa/0x480
       elevator_set_default+0x375/0x440
       blk_register_queue+0x3f3/0x4e0
       __add_disk+0x6b8/0xdb0
       add_disk_fwnode+0x100/0x3a0
       nbd_dev_add+0x733/0xb60
       nbd_init+0x168/0x1f0
       do_one_initcall+0x250/0x870
       do_initcall_level+0x10a/0x1a0
       do_initcalls+0x59/0xa0
       kernel_init_freeable+0x29d/0x3e0
       kernel_init+0x22/0x1d0
       ret_from_fork+0x514/0xb70
       ret_from_fork_asm+0x1a/0x30

-> #3 (&q->elevator_lock){+.+.}-{4:4}:
       __mutex_lock+0x19d/0x1550
       elevator_change+0x1af/0x480
       elevator_set_none+0xb5/0x140
       blk_mq_update_nr_hw_queues+0x5ef/0x19f0
       nbd_start_device+0x189/0xb30
       nbd_genl_connect+0x167d/0x1cd0
       genl_family_rcv_msg_doit+0x233/0x340
       genl_rcv_msg+0x614/0x7a0
       netlink_rcv_skb+0x226/0x4a0
       genl_rcv+0x28/0x40
       netlink_unicast+0x7bd/0x940
       netlink_sendmsg+0x813/0xb40
       sock_sendmsg_nosec+0x14e/0x190
       ____sys_sendmsg+0x54e/0x850
       ___sys_sendmsg+0x2a5/0x360
       __x64_sys_sendmsg+0x1b1/0x290
       do_syscall_64+0x166/0x520
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&q->q_usage_counter(io)#49){++++}-{0:0}:
       blk_alloc_queue+0x544/0x690
       __blk_mq_alloc_disk+0x194/0x390
       nbd_dev_add+0x494/0xb60
       nbd_init+0x168/0x1f0
       do_one_initcall+0x250/0x870
       do_initcall_level+0x10a/0x1a0
       do_initcalls+0x59/0xa0
       kernel_init_freeable+0x29d/0x3e0
       kernel_init+0x22/0x1d0
       ret_from_fork+0x514/0xb70
       ret_from_fork_asm+0x1a/0x30

-> #1 (fs_reclaim){+.+.}-{0:0}:
       fs_reclaim_acquire+0x71/0x100
       kmem_cache_alloc_noprof+0x5f/0x600
       __kernfs_iattrs+0xdd/0x380
       kernfs_iop_setattr+0xe6/0x3f0
       notify_change+0xbba/0xea0
       do_truncate+0x1c2/0x250
       path_openat+0x15b5/0x1d60
       do_file_open+0x23e/0x4a0
       do_sys_openat2+0x115/0x200
       __x64_sys_openat+0x138/0x170
       do_syscall_64+0x166/0x520
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&root->kernfs_iattr_rwsem){++++}-{4:4}:
       __lock_acquire+0x164c/0x2de0
       lock_acquire+0x115/0x350
       down_write+0x96/0x200
       kernfs_link_sibling+0x4c7/0x5a0
       kernfs_add_one+0x2db/0x6f0
       kernfs_create_dir_ns+0x1a1/0x230
       sysfs_create_dir_ns+0x12f/0x2a0
       kobject_add_internal+0x622/0xcd0
       kobject_add+0x163/0x240
       device_add+0x3fa/0xb80
       device_create_with_groups+0x26a/0x300
       led_classdev_register_ext+0x498/0x990
       input_leds_connect+0x4de/0x750
       input_register_device+0xd08/0x1150
       hidp_session_probe+0x1a5/0x8a0
       l2cap_register_user+0xbd/0x1d0
       hidp_connection_add+0x1570/0x1a00
       hidp_sock_ioctl+0x403/0x650
       sock_do_ioctl+0x101/0x320
       sock_ioctl+0x57a/0x7e0
       __se_sys_ioctl+0xfc/0x170
       do_syscall_64+0x166/0x520
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

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 syz.0.5857/19177: 5, last CPU#1:
 #0: ffff88816a5682f8 (&conn->lock#2){+.+.}-{4:4}, at: l2cap_register_user+0x34/0x1d0
 #1: ffffffff903f9c88 (hidp_session_sem){++++}-{4:4}, at: hidp_session_probe+0x98/0x8a0
 #2: ffffffff8fcc8820 (input_mutex){+.+.}-{4:4}, at: input_register_device+0xa7f/0x1150
 #3: ffff88816efcc2f0 (&led_cdev->led_access){+.+.}-{4:4}, at: led_classdev_register_ext+0x45e/0x990
 #4: ffff8881012d4180 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_add_one+0x41/0x6f0

stack backtrace:
CPU: 1 UID: 0 PID: 19177 Comm: syz.0.5857 Not tainted syzkaller #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+0xe8/0x150
 print_circular_bug+0x2e2/0x300
 check_noncircular+0x12f/0x150
 __lock_acquire+0x164c/0x2de0
 lock_acquire+0x115/0x350
 down_write+0x96/0x200
 kernfs_link_sibling+0x4c7/0x5a0
 kernfs_add_one+0x2db/0x6f0
 kernfs_create_dir_ns+0x1a1/0x230
 sysfs_create_dir_ns+0x12f/0x2a0
 kobject_add_internal+0x622/0xcd0
 kobject_add+0x163/0x240
 device_add+0x3fa/0xb80
 device_create_with_groups+0x26a/0x300
 led_classdev_register_ext+0x498/0x990
 input_leds_connect+0x4de/0x750
 input_register_device+0xd08/0x1150
 hidp_session_probe+0x1a5/0x8a0
 l2cap_register_user+0xbd/0x1d0
 hidp_connection_add+0x1570/0x1a00
 hidp_sock_ioctl+0x403/0x650
 sock_do_ioctl+0x101/0x320
 sock_ioctl+0x57a/0x7e0
 __se_sys_ioctl+0xfc/0x170
 do_syscall_64+0x166/0x520
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff5f2d9e199
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ff5f3b8c028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ff5f3025fa0 RCX: 00007ff5f2d9e199
RDX: 0000200000000500 RSI: 00000000400448c8 RDI: 000000000000000b
RBP: 00007ff5f2e350b8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff5f3026038 R14: 00007ff5f3025fa0 R15: 00007ffe6e625a58
 </TASK>
