======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
khidpd_00010003/6872 is trying to acquire lock:
ffffffff8ea848a0 (fs_reclaim){+.+.}-{0:0}, at: kmem_cache_alloc_node_noprof+0x6a/0x610

but task is already holding lock:
ffffffff90196540 (uevent_sock_mutex){+.+.}-{4:4}, at: kobject_uevent_net_broadcast+0x27e/0x560

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #10 (uevent_sock_mutex){+.+.}-{4:4}:
       __mutex_lock+0x19d/0x1550
       kobject_uevent_net_broadcast+0x27e/0x560
       kobject_uevent_env+0x566/0x9e0
       device_add+0x544/0xb80
       device_create+0x269/0x300
       msr_device_create+0x33/0x50
       cpuhp_invoke_callback+0x434/0x810
       cpuhp_thread_fun+0x362/0x780
       smpboot_thread_fn+0x57c/0xa80
       kthread+0x388/0x470
       ret_from_fork+0x514/0xb70
       ret_from_fork_asm+0x1a/0x30

-> #9 (cpuhp_state-up){+.+.}-{0:0}:
       cpuhp_thread_fun+0x127/0x780
       smpboot_thread_fn+0x57c/0xa80
       kthread+0x388/0x470
       ret_from_fork+0x514/0xb70
       ret_from_fork_asm+0x1a/0x30

-> #8 (cpu_hotplug_lock){++++}-{0:0}:
       cpus_read_lock+0x42/0x160
       static_key_slow_inc+0x12/0x30
       tcp_md5_do_add+0x1d4/0x390
       tcp_v6_parse_md5_keys+0x550/0x670
       do_tcp_setsockopt+0x1250/0x1f80
       do_sock_setsockopt+0x17c/0x1b0
       __x64_sys_setsockopt+0x13d/0x1b0
       do_syscall_64+0x174/0x580
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #7 (sk_lock-AF_INET6){+.+.}-{0:0}:
       lock_sock_nested+0x41/0x100
       tls_sw_sendmsg+0x161/0x2860
       sock_sendmsg_nosec+0x90/0x180
       ____sys_sendmsg+0x54e/0x850
       ___sys_sendmsg+0x2a5/0x360
       __x64_sys_sendmsg+0x1b1/0x290
       do_syscall_64+0x174/0x580
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #6 (&ctx->tx_lock){+.+.}-{4:4}:
       __mutex_lock+0x19d/0x1550
       tls_sw_sendmsg+0x13c/0x2860
       sock_sendmsg_nosec+0x90/0x180
       sock_sendmsg+0x1ca/0x2d0
       __sock_xmit+0x245/0x4f0
       nbd_disconnect+0x3ad/0x560
       nbd_disconnect_and_put+0x32/0x280
       nbd_genl_disconnect+0x4af/0x590
       genl_family_rcv_msg_doit+0x233/0x340
       genl_rcv_msg+0x614/0x7a0
       netlink_rcv_skb+0x226/0x4a0
       genl_rcv+0x28/0x40
       netlink_unicast+0x7bb/0x940
       netlink_sendmsg+0x813/0xb40
       sock_sendmsg_nosec+0x13a/0x180
       ____sys_sendmsg+0x54e/0x850
       ___sys_sendmsg+0x2a5/0x360
       __x64_sys_sendmsg+0x1b1/0x290
       do_syscall_64+0x174/0x580
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #5 (&nsock->tx_lock){+.+.}-{4:4}:
       __mutex_lock+0x19d/0x1550
       nbd_queue_rq+0x373/0x1150
       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+0xa8e/0x14e0
       worker_thread+0xa47/0xfb0
       kthread+0x388/0x470
       ret_from_fork+0x514/0xb70
       ret_from_fork_asm+0x1a/0x30

-> #4 (&cmd->lock){+.+.}-{4:4}:
       __mutex_lock+0x19d/0x1550
       nbd_queue_rq+0xc1/0x1150
       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+0xa8e/0x14e0
       worker_thread+0xa47/0xfb0
       kthread+0x388/0x470
       ret_from_fork+0x514/0xb70
       ret_from_fork_asm+0x1a/0x30

-> #3 (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+0x6cb/0xe30
       add_disk_fwnode+0xfb/0x4b0
       nbd_dev_add+0x733/0xb60
       nbd_init+0x15f/0x1e0
       do_one_initcall+0x250/0x870
       do_initcall_level+0x10a/0x1a0
       do_initcalls+0x59/0xa0
       kernel_init_freeable+0x29d/0x3e0
       kernel_init+0x1d/0x1d0
       ret_from_fork+0x514/0xb70
       ret_from_fork_asm+0x1a/0x30

-> #2 (&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+0x1597/0x1c10
       genl_family_rcv_msg_doit+0x233/0x340
       genl_rcv_msg+0x614/0x7a0
       netlink_rcv_skb+0x226/0x4a0
       genl_rcv+0x28/0x40
       netlink_unicast+0x7bb/0x940
       netlink_sendmsg+0x813/0xb40
       sock_sendmsg_nosec+0x13a/0x180
       ____sys_sendmsg+0x54e/0x850
       ___sys_sendmsg+0x2a5/0x360
       __x64_sys_sendmsg+0x1b1/0x290
       do_syscall_64+0x174/0x580
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&q->q_usage_counter(io)#52){++++}-{0:0}:
       blk_alloc_queue+0x544/0x690
       __blk_mq_alloc_disk+0x194/0x390
       nbd_dev_add+0x494/0xb60
       nbd_init+0x15f/0x1e0
       do_one_initcall+0x250/0x870
       do_initcall_level+0x10a/0x1a0
       do_initcalls+0x59/0xa0
       kernel_init_freeable+0x29d/0x3e0
       kernel_init+0x1d/0x1d0
       ret_from_fork+0x514/0xb70
       ret_from_fork_asm+0x1a/0x30

-> #0 (fs_reclaim){+.+.}-{0:0}:
       __lock_acquire+0x1520/0x2cf0
       lock_acquire+0x106/0x350
       fs_reclaim_acquire+0x71/0x100
       kmem_cache_alloc_node_noprof+0x6a/0x610
       __alloc_skb+0x276/0x7a0
       alloc_uevent_skb+0x7d/0x230
       kobject_uevent_net_broadcast+0x2fa/0x560
       kobject_uevent_env+0x566/0x9e0
       led_trigger_set+0x708/0x940
       led_classdev_unregister+0xa8/0x280
       input_leds_disconnect+0x96/0x140
       __input_unregister_device+0x356/0x650
       input_unregister_device+0x9b/0x100
       hidp_session_remove+0x181/0x2b0
       l2cap_unregister_user+0x145/0x160
       hidp_session_unregister_conn+0x8b/0xc0
       hidp_session_thread+0x399/0x400
       kthread+0x388/0x470
       ret_from_fork+0x514/0xb70
       ret_from_fork_asm+0x1a/0x30

other info that might help us debug this:

Chain exists of:
  fs_reclaim --> cpuhp_state-up --> uevent_sock_mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(uevent_sock_mutex);
                               lock(cpuhp_state-up);
                               lock(uevent_sock_mutex);
  lock(fs_reclaim);

 *** DEADLOCK ***

5 locks held by khidpd_00010003/6872:
 #0: ffff8881a7e532f8 (&conn->lock#2){+.+.}-{4:4}, at: l2cap_unregister_user+0x35/0x160
 #1: ffffffff8ff9e488 (hidp_session_sem){++++}-{4:4}, at: hidp_session_remove+0x2c/0x2b0
 #2: ffffffff8f8659c0 (input_mutex){+.+.}-{4:4}, at: __input_unregister_device+0x2d8/0x650
 #3: ffff8881844be210 (&led_cdev->trigger_lock){+.+.}-{4:4}, at: led_classdev_unregister+0x75/0x280
 #4: ffffffff90196540 (uevent_sock_mutex){+.+.}-{4:4}, at: kobject_uevent_net_broadcast+0x27e/0x560

stack backtrace:
CPU: 0 UID: 0 PID: 6872 Comm: khidpd_00010003 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+0x2e1/0x300
 check_noncircular+0x12e/0x150
 __lock_acquire+0x1520/0x2cf0
 lock_acquire+0x106/0x350
 fs_reclaim_acquire+0x71/0x100
 kmem_cache_alloc_node_noprof+0x6a/0x610
 __alloc_skb+0x276/0x7a0
 alloc_uevent_skb+0x7d/0x230
 kobject_uevent_net_broadcast+0x2fa/0x560
 kobject_uevent_env+0x566/0x9e0
 led_trigger_set+0x708/0x940
 led_classdev_unregister+0xa8/0x280
 input_leds_disconnect+0x96/0x140
 __input_unregister_device+0x356/0x650
 input_unregister_device+0x9b/0x100
 hidp_session_remove+0x181/0x2b0
 l2cap_unregister_user+0x145/0x160
 hidp_session_unregister_conn+0x8b/0xc0
 hidp_session_thread+0x399/0x400
 kthread+0x388/0x470
 ret_from_fork+0x514/0xb70
 ret_from_fork_asm+0x1a/0x30
 </TASK>
