INFO: task kworker/u8:3:5848 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u8:3    state:D stack:20440 pid:5848  tgid:5848  ppid:2      task_flags:0x4208060 flags:0x00080000
Workqueue: netns cleanup_net
Call Trace:
 <TASK>
 __schedule+0x17e4/0x4de0
 schedule+0x164/0x360
 schedule_preempt_disabled+0x13/0x30
 __mutex_lock+0x7fe/0x1300
 rdma_dev_change_netns+0x39/0x300
 rdma_dev_exit_net+0x209/0x350
 ops_undo_list+0x49f/0x940
 cleanup_net+0x4df/0x820
 process_scheduled_works+0xafc/0x17d0
 worker_thread+0xda6/0x1360
 kthread+0x726/0x8b0
 ret_from_fork+0x4d3/0x870
 ret_from_fork_asm+0x1a/0x30
 </TASK>
INFO: task syz.1.12842:11692 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.1.12842     state:D stack:22776 pid:11692 tgid:11688 ppid:5805   task_flags:0x400140 flags:0x00080003
Call Trace:
 <TASK>
 __schedule+0x17e4/0x4de0
 schedule+0x164/0x360
 schedule_timeout+0xc3/0x2c0
 wait_for_completion+0x2cc/0x5e0
 disable_device+0x1c6/0x330
 __ib_unregister_device+0x2cb/0x3f0
 ib_unregister_device_and_put+0xb8/0xf0
 nldev_dellink+0x288/0x320
 rdma_nl_rcv+0x6d7/0xa10
 netlink_unicast+0x80f/0x9b0
 netlink_sendmsg+0x813/0xb40
 ____sys_sendmsg+0xa84/0xaf0
 ___sys_sendmsg+0x2a5/0x360
 __x64_sys_sendmsg+0x1bd/0x2a0
 do_syscall_64+0xf0/0xfa0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f683c79c819
RSP: 002b:00007f683d621028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f683ca16090 RCX: 00007f683c79c819
RDX: 0000000000000000 RSI: 00002000000002c0 RDI: 0000000000000005
RBP: 00007f683c832c91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f683ca16128 R14: 00007f683ca16090 R15: 00007fffde2ebff8
 </TASK>

Showing all locks held in the system:
1 lock held by rcu_exp_gp_kthr/18:
1 lock held by khungtaskd/34:
 #0: ffffffff8e33eba0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180
2 locks held by getty/5639:
 #0: ffff888174b440a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70
 #1: ffffc9000356b2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x45f/0x14a0
3 locks held by kworker/u8:2/5816:
 #0: ffff88811199c948 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_scheduled_works+0x9d4/0x17d0
 #1: ffffc90003c97ba0 ((work_completion)(&(&net->ipv6.addr_chk_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0xa0f/0x17d0
 #2: ffffffff8f6d98c8 (rtnl_mutex){+.+.}-{4:4}, at: addrconf_verify_work+0x19/0x30
4 locks held by kworker/u8:3/5848:
 #0: ffff888100ef7948 ((wq_completion)netns){+.+.}-{0:0}, at: process_scheduled_works+0x9d4/0x17d0
 #1: ffffc90003ff7ba0 (net_cleanup_work){+.+.}-{0:0}, at: process_scheduled_works+0xa0f/0x17d0
 #2: ffffffff8f6ccad0 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xfe/0x820
 #3: ffff8881ac4c0700 (&device->unregistration_lock){+.+.}-{4:4}, at: rdma_dev_change_netns+0x39/0x300
2 locks held by syz.1.12842/11692:
 #0: ffffffff99fc5ed8 (&rdma_nl_types[idx].sem){.+.+}-{4:4}, at: rdma_nl_rcv+0x32b/0xa10
 #1: ffff8881ac4c0700 (&device->unregistration_lock){+.+.}-{4:4}, at: __ib_unregister_device+0x284/0x3f0
2 locks held by syz.2.14228/15932:
 #0: ffffffff8f6ccad0 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x336/0x4e0
 #1: ffff8881ac4c0700 (&device->unregistration_lock){+.+.}-{4:4}, at: rdma_dev_change_netns+0x39/0x300
2 locks held by syz.3.14873/18021:
 #0: ffffffff8f6ccad0 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x336/0x4e0
 #1: ffff8881ac4c0700 (&device->unregistration_lock){+.+.}-{4:4}, at: rdma_dev_change_netns+0x39/0x300
2 locks held by syz.5.15407/19780:
 #0: ffffffff8f6ccad0 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x336/0x4e0
 #1: ffff8881ac4c0700 (&device->unregistration_lock){+.+.}-{4:4}, at: rdma_dev_change_netns+0x39/0x300
2 locks held by syz.5.15407/19781:
 #0: ffffffff8f6ccad0 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x336/0x4e0
 #1: ffff8881ac4c0700 (&device->unregistration_lock){+.+.}-{4:4}, at: rdma_dev_change_netns+0x39/0x300
1 lock held by syz.4.15539/20245:
 #0: ffffffff8f6d98c8 (rtnl_mutex){+.+.}-{4:4}, at: tun_chr_close+0x3e/0x1c0
2 locks held by syz.4.15539/20246:
 #0: ffffffff8f6d98c8 (rtnl_mutex){+.+.}-{4:4}, at: rtnetlink_rcv_msg+0x722/0xbe0
 #1: ffffffff8e344638 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x3f2/0x7e0
4 locks held by syz.0.15540/20248:
 #0: ffff88819807e208 (&sb->s_type->i_mutex_key#11){+.+.}-{4:4}, at: sock_close+0x9b/0x240
 #1: ffffffff8f73dc70 ((netlink_chain).rwsem){++++}-{4:4}, at: blocking_notifier_call_chain+0x54/0x90
 #2: ffff8881098eb0d8 (&nft_net->commit_mutex){+.+.}-{4:4}, at: nft_rcv_nl_event+0x13d/0xdb0
 #3: ffffffff8e344638 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x32f/0x7e0
1 lock held by syz.0.15540/20249:
 #0: ffffffff8f6d98c8 (rtnl_mutex){+.+.}-{4:4}, at: __tun_chr_ioctl+0x3bc/0x1e10
1 lock held by syz.0.15540/20250:
 #0: ffffffff8f6d98c8 (rtnl_mutex){+.+.}-{4:4}, at: rtnetlink_rcv_msg+0x722/0xbe0

=============================================

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 34 Comm: khungtaskd 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+0x1a9/0x280
 nmi_cpu_backtrace+0x3a9/0x3e0
 nmi_trigger_cpumask_backtrace+0x17a/0x300
 watchdog+0xf5b/0xfa0
 kthread+0x726/0x8b0
 ret_from_fork+0x4d3/0x870
 ret_from_fork_asm+0x1a/0x30
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 0 Comm: swapper/0 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
RIP: 0010:pv_native_safe_halt+0xf/0x20
Code: 37 5d 02 e9 03 ed 02 00 cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa eb 07 0f 00 2d c3 1d 27 00 fb f4 <c3> cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc 90 90 90 90 90
RSP: 0018:ffffffff8e007d80 EFLAGS: 00000286
RAX: 21cc0ee99e39e800 RBX: ffffffff8198cb6b RCX: 21cc0ee99e39e800
RDX: 0000000000000001 RSI: ffffffff8db33656 RDI: ffffffff8bff20e0
RBP: ffffffff8e007ea8 R08: ffff888121032fdb R09: 1ffff110242065fb
R10: dffffc0000000000 R11: ffffed10242065fc R12: 1ffffffff1c12a40
R13: 1ffffffff1c00fbc R14: 0000000000000000 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff88818e4dc000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7bd9419b6f CR3: 000000011561c000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 default_idle+0x9/0x20
 default_idle_call+0x72/0xb0
 do_idle+0x1eb/0x4e0
 cpu_startup_entry+0x43/0x60
 rest_init+0x2de/0x300
 start_kernel+0x3ad/0x410
 x86_64_start_reservations+0x24/0x30
 x86_64_start_kernel+0x143/0x1c0
 common_startup_64+0x13e/0x147
 </TASK>
