INFO: task udevd:5806 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:udevd           state:D stack:22120 pid:5806  tgid:5806  ppid:5253   task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 __schedule+0x14ef/0x4fb0
 preempt_schedule_common+0x82/0xd0
 preempt_schedule_thunk+0x16/0x30
 _raw_spin_unlock_irqrestore+0x30/0x80
 lockdep_hardirqs_on+0x7a/0x110
 </TASK>

Showing all locks held in the system:
1 lock held by pool_workqueue_/3:
 #0: ffffffff8e360c78 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x38d/0x770
1 lock held by khungtaskd/35:
 #0: ffffffff8e35a360 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180
1 lock held by klogd/5242:
 #0: ffff88812103a918 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2a/0x140
2 locks held by getty/5629:
 #0: ffff88816cd110a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70
 #1: ffffc9000357b2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x45c/0x13c0
1 lock held by udevd/8138:
 #0: ffff8881af2ff358 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_open+0xe0/0xd30
7 locks held by kworker/u9:10/10251:
4 locks held by kworker/u8:6/13196:
 #0: ffff888100ef7948 ((wq_completion)netns){+.+.}-{0:0}, at: process_scheduled_works+0x9d4/0x17a0
 #1: ffffc90004737bc0 (net_cleanup_work){+.+.}-{0:0}, at: process_scheduled_works+0xa0f/0x17a0
 #2: ffffffff8f79bbb0 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xfe/0x7b0
 #3: ffffffff8f7aa548 (rtnl_mutex){+.+.}-{4:4}, at: cfg80211_pernet_exit+0x19/0x120
1 lock held by syz.1.6175/29460:
 #0: ffffffff8f7aa548 (rtnl_mutex){+.+.}-{4:4}, at: ppp_release+0x87/0x1f0

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

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 35 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+0xe8/0x150
 nmi_cpu_backtrace+0x274/0x2d0
 nmi_trigger_cpumask_backtrace+0x17a/0x300
 sys_info+0x135/0x170
 watchdog+0xf90/0xfe0
 kthread+0x726/0x8b0
 ret_from_fork+0x51b/0xa40
 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: 13196 Comm: kworker/u8:6 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
Workqueue: netns cleanup_net
RIP: 0010:unwind_get_return_address+0x4d/0x90
Code: c0 75 4c 83 3b 00 74 3a 48 83 c3 48 49 89 df 49 c1 ef 03 43 80 3c 37 00 74 08 48 89 df e8 bb e0 b4 00 48 8b 3b e8 73 11 19 00 <85> c0 74 14 43 80 3c 37 00 74 08 48 89 df e8 a0 e0 b4 00 48 8b 03
RSP: 0018:ffffc90004737268 EFLAGS: 00000202
RAX: 0000000000000001 RBX: ffffc900047372d0 RCX: 0000000000000000
RDX: 0000000000000001 RSI: ffffffff8dd42d89 RDI: ffffffff822977dd
RBP: ffffc90004737310 R08: ffffc900047375e8 R09: 0000000000000000
R10: ffffc900047372d8 R11: fffff520008e6e5d R12: ffff88810a688000
R13: ffff888197be4870 R14: dffffc0000000000 R15: 1ffff920008e6e5a
FS:  0000000000000000(0000) GS:ffff88818e318000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000001000 CR3: 0000000113b5e000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 arch_stack_walk+0xfb/0x150
 stack_trace_save+0xa9/0x100
 kasan_save_stack+0x3e/0x60
 kasan_record_aux_stack+0xbd/0xd0
 call_rcu+0xee/0x890
 kernfs_put+0x18e/0x470
 kernfs_remove_by_name_ns+0xb7/0x130
 sysfs_remove_group+0xfc/0x2e0
 sysfs_remove_groups+0x54/0xb0
 ib_free_port_attrs+0xc5/0x3b0
 rdma_dev_exit_net+0x1de/0x350
 ops_undo_list+0x49f/0x940
 cleanup_net+0x4df/0x7b0
 process_scheduled_works+0xaec/0x17a0
 worker_thread+0x89f/0xd90
 kthread+0x726/0x8b0
 ret_from_fork+0x51b/0xa40
 ret_from_fork_asm+0x1a/0x30
 </TASK>
