syzbot

=====================================================
WARNING: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected
syzkaller #0 Tainted: G             L     
-----------------------------------------------------
syz.7.8974/6651 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire:
ffffffff8e40c058 (tasklist_lock){.+.+}-{3:3}, at: send_sigurg+0x12b/0x420 fs/fcntl.c:978

and this task is already holding:
ffff88803f015920 (&f_owner->lock){....}-{3:3}, at: send_sigurg+0x55/0x420 fs/fcntl.c:962
which would create a new lock dependency:
 (&f_owner->lock){....}-{3:3} -> (tasklist_lock){.+.+}-{3:3}

but this new dependency connects a SOFTIRQ-irq-safe lock:
 (&client->buffer_lock){..-.}-{3:3}

... which became SOFTIRQ-irq-safe at:
  lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
  __raw_spin_lock include/linux/spinlock_api_smp.h:158 [inline]
  _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
  spin_lock include/linux/spinlock.h:341 [inline]
  evdev_pass_values+0xb9/0xbd0 drivers/input/evdev.c:261
  evdev_events+0x1e6/0x340 drivers/input/evdev.c:306
  input_pass_values+0x288/0x890 drivers/input/input.c:128
  input_event_dispose+0x3e5/0x6b0 drivers/input/input.c:353
  input_event+0x89/0xe0 drivers/input/input.c:396
  hidinput_hid_event+0x1487/0x1e60 drivers/hid/hid-input.c:1747
  hid_process_event+0x4be/0x620 drivers/hid/hid-core.c:1565
  hid_process_report drivers/hid/hid-core.c:1713 [inline]
  hid_report_raw_event+0xe8f/0x1720 drivers/hid/hid-core.c:2074
  __hid_input_report drivers/hid/hid-core.c:2144 [inline]
  hid_input_report+0x44b/0x580 drivers/hid/hid-core.c:2166
  hid_irq_in+0x47e/0x6d0 drivers/hid/usbhid/hid-core.c:286
  __usb_hcd_giveback_urb+0x376/0x540 drivers/usb/core/hcd.c:1657
  dummy_timer+0xbbd/0x45d0 drivers/usb/gadget/udc/dummy_hcd.c:1995
  __run_hrtimer kernel/time/hrtimer.c:1785 [inline]
  __hrtimer_run_queues+0x53a/0xcc0 kernel/time/hrtimer.c:1849
  hrtimer_run_softirq+0x182/0x5a0 kernel/time/hrtimer.c:1866
  handle_softirqs+0x22a/0x870 kernel/softirq.c:622
  __do_softirq kernel/softirq.c:656 [inline]
  invoke_softirq kernel/softirq.c:496 [inline]
  __irq_exit_rcu+0x5f/0x150 kernel/softirq.c:723
  irq_exit_rcu+0x9/0x30 kernel/softirq.c:739
  instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1056 [inline]
  sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1056
  asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
  native_safe_halt arch/x86/include/asm/irqflags.h:48 [inline]
  pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:62
  arch_safe_halt arch/x86/kernel/process.c:766 [inline]
  default_idle+0x9/0x20 arch/x86/kernel/process.c:767
  default_idle_call+0x72/0xb0 kernel/sched/idle.c:122
  cpuidle_idle_call kernel/sched/idle.c:191 [inline]
  do_idle+0x1ba/0x5d0 kernel/sched/idle.c:341
  cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:439
  rest_init+0x2de/0x300 init/main.c:760
  start_kernel+0x385/0x3d0 init/main.c:1210
  x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310
  x86_64_start_kernel+0x143/0x1c0 arch/x86/kernel/head64.c:291
  common_startup_64+0x13e/0x147

to a SOFTIRQ-irq-unsafe lock:
 (tasklist_lock){.+.+}-{3:3}

... which became SOFTIRQ-irq-unsafe at:
...
  lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
  __raw_read_lock include/linux/rwlock_api_smp.h:161 [inline]
  _raw_read_lock+0x36/0x50 kernel/locking/spinlock.c:228
  __do_wait+0xde/0x740 kernel/exit.c:1678
  do_wait+0x1e7/0x540 kernel/exit.c:1722
  kernel_wait+0xd6/0x1c0 kernel/exit.c:1898
  call_usermodehelper_exec_sync kernel/umh.c:136 [inline]
  call_usermodehelper_exec_work+0xbe/0x230 kernel/umh.c:163
  process_one_work kernel/workqueue.c:3276 [inline]
  process_scheduled_works+0xb6e/0x18c0 kernel/workqueue.c:3359
  worker_thread+0xa53/0xfc0 kernel/workqueue.c:3440
  kthread+0x388/0x470 kernel/kthread.c:436
  ret_from_fork+0x51e/0xb90 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:
  &client->buffer_lock --> &f_owner->lock --> tasklist_lock

 Possible interrupt unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(tasklist_lock);
                               local_irq_disable();
                               lock(&client->buffer_lock);
                               lock(&f_owner->lock);
  <Interrupt>
    lock(&client->buffer_lock);

 *** DEADLOCK ***

2 locks held by syz.7.8974/6651:
 #0: ffff8880226bde60 (&u->lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock.h:341 [inline]
 #0: ffff8880226bde60 (&u->lock){+.+.}-{3:3}, at: queue_oob+0x1b6/0x4f0 net/unix/af_unix.c:2331
 #1: ffff88803f015920 (&f_owner->lock){....}-{3:3}, at: send_sigurg+0x55/0x420 fs/fcntl.c:962

the dependencies between SOFTIRQ-irq-safe lock and the holding lock:
  -> (&client->buffer_lock){..-.}-{3:3} {
     IN-SOFTIRQ-W at:
                        lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
                        __raw_spin_lock include/linux/spinlock_api_smp.h:158 [inline]
                        _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
                        spin_lock include/linux/spinlock.h:341 [inline]
                        evdev_pass_values+0xb9/0xbd0 drivers/input/evdev.c:261
                        evdev_events+0x1e6/0x340 drivers/input/evdev.c:306
                        input_pass_values+0x288/0x890 drivers/input/input.c:128
                        input_event_dispose+0x3e5/0x6b0 drivers/input/input.c:353
                        input_event+0x89/0xe0 drivers/input/input.c:396
                        hidinput_hid_event+0x1487/0x1e60 drivers/hid/hid-input.c:1747
                        hid_process_event+0x4be/0x620 drivers/hid/hid-core.c:1565
                        hid_process_report drivers/hid/hid-core.c:1713 [inline]
                        hid_report_raw_event+0xe8f/0x1720 drivers/hid/hid-core.c:2074
                        __hid_input_report drivers/hid/hid-core.c:2144 [inline]
                        hid_input_report+0x44b/0x580 drivers/hid/hid-core.c:2166
                        hid_irq_in+0x47e/0x6d0 drivers/hid/usbhid/hid-core.c:286
                        __usb_hcd_giveback_urb+0x376/0x540 drivers/usb/core/hcd.c:1657
                        dummy_timer+0xbbd/0x45d0 drivers/usb/gadget/udc/dummy_hcd.c:1995
                        __run_hrtimer kernel/time/hrtimer.c:1785 [inline]
                        __hrtimer_run_queues+0x53a/0xcc0 kernel/time/hrtimer.c:1849
                        hrtimer_run_softirq+0x182/0x5a0 kernel/time/hrtimer.c:1866
                        handle_softirqs+0x22a/0x870 kernel/softirq.c:622
                        __do_softirq kernel/softirq.c:656 [inline]
                        invoke_softirq kernel/softirq.c:496 [inline]
                        __irq_exit_rcu+0x5f/0x150 kernel/softirq.c:723
                        irq_exit_rcu+0x9/0x30 kernel/softirq.c:739
                        instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1056 [inline]
                        sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1056
                        asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
                        native_safe_halt arch/x86/include/asm/irqflags.h:48 [inline]
                        pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:62
                        arch_safe_halt arch/x86/kernel/process.c:766 [inline]
                        default_idle+0x9/0x20 arch/x86/kernel/process.c:767
                        default_idle_call+0x72/0xb0 kernel/sched/idle.c:122
                        cpuidle_idle_call kernel/sched/idle.c:191 [inline]
                        do_idle+0x1ba/0x5d0 kernel/sched/idle.c:341
                        cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:439
                        rest_init+0x2de/0x300 init/main.c:760
                        start_kernel+0x385/0x3d0 init/main.c:1210
                        x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310
                        x86_64_start_kernel+0x143/0x1c0 arch/x86/kernel/head64.c:291
                        common_startup_64+0x13e/0x147
     INITIAL USE at:
                       lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
                       __raw_spin_lock include/linux/spinlock_api_smp.h:158 [inline]
                       _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
                       spin_lock include/linux/spinlock.h:341 [inline]
                       evdev_pass_values+0xb9/0xbd0 drivers/input/evdev.c:261
                       evdev_events+0x1e6/0x340 drivers/input/evdev.c:306
                       input_pass_values+0x288/0x890 drivers/input/input.c:128
                       input_event_dispose+0x330/0x6b0 drivers/input/input.c:342
                       input_inject_event+0x1dd/0x340 drivers/input/input.c:424
                       evdev_write+0x325/0x4c0 drivers/input/evdev.c:528
                       vfs_write+0x29a/0xb90 fs/read_write.c:686
                       ksys_write+0x150/0x270 fs/read_write.c:740
                       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
                       do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
                       entry_SYSCALL_64_after_hwframe+0x77/0x7f
   }
   ... key      at: [<ffffffff9a60b800>] evdev_open.__key.27+0x0/0x20
 -> (&new->fa_lock){...-}-{3:3} {
    IN-SOFTIRQ-R at:
                      lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
                      __raw_read_lock_irqsave include/linux/rwlock_api_smp.h:172 [inline]
                      _raw_read_lock_irqsave+0x48/0x60 kernel/locking/spinlock.c:236
                      kill_fasync_rcu fs/fcntl.c:1135 [inline]
                      kill_fasync+0x199/0x4d0 fs/fcntl.c:1159
                      sock_wake_async+0x137/0x160 net/socket.c:-1
                      sk_wake_async_rcu include/net/sock.h:2579 [inline]
                      sock_def_readable+0x3c1/0x580 net/core/sock.c:3613
                      tcp_data_queue+0x1e2e/0x5e50 net/ipv4/tcp_input.c:5714
                      tcp_rcv_established+0xf45/0x2740 net/ipv4/tcp_input.c:6708
                      tcp_v4_do_rcv+0xa90/0x1430 net/ipv4/tcp_ipv4.c:1884
                      tcp_v4_rcv+0x2825/0x31f0 net/ipv4/tcp_ipv4.c:2319
                      ip_protocol_deliver_rcu+0x221/0x440 net/ipv4/ip_input.c:207
                      ip_local_deliver_finish+0x3bb/0x6f0 net/ipv4/ip_input.c:241
                      NF_HOOK+0x336/0x3c0 include/linux/netfilter.h:318
                      NF_HOOK+0x336/0x3c0 include/linux/netfilter.h:318
                      __netif_receive_skb_one_core net/core/dev.c:6164 [inline]
                      __netif_receive_skb net/core/dev.c:6277 [inline]
                      process_backlog+0xaa3/0x1950 net/core/dev.c:6628
                      __napi_poll+0xae/0x340 net/core/dev.c:7692
                      napi_poll net/core/dev.c:7755 [inline]
                      net_rx_action+0x627/0xf70 net/core/dev.c:7912
                      handle_softirqs+0x22a/0x870 kernel/softirq.c:622
                      do_softirq+0x76/0xd0 kernel/softirq.c:523
                      __local_bh_enable_ip+0xf8/0x130 kernel/softirq.c:450
                      sk_stream_wait_memory+0x72b/0xf80 net/core/stream.c:149
                      tcp_sendmsg_locked+0x23ba/0x5490 net/ipv4/tcp.c:1418
                      tcp_sendmsg+0x2f/0x50 net/ipv4/tcp.c:1465
                      sock_sendmsg_nosec net/socket.c:727 [inline]
                      __sock_sendmsg net/socket.c:742 [inline]
                      __sys_sendto+0x5de/0x710 net/socket.c:2206
                      __do_sys_sendto net/socket.c:2213 [inline]
                      __se_sys_sendto net/socket.c:2209 [inline]
                      __x64_sys_sendto+0xde/0x100 net/socket.c:2209
                      do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
                      do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
                      entry_SYSCALL_64_after_hwframe+0x77/0x7f
    INITIAL USE at:
                     lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
                     __raw_write_lock_irq include/linux/rwlock_api_smp.h:211 [inline]
                     _raw_write_lock_irq+0x3d/0x50 kernel/locking/spinlock.c:326
                     fasync_remove_entry+0xf1/0x1c0 fs/fcntl.c:1012
                     tun_chr_fasync+0x87/0x1a0 drivers/net/tun.c:3380
                     __fput+0x8a5/0xa70 fs/file_table.c:466
                     task_work_run+0x1d9/0x270 kernel/task_work.c:233
                     exit_task_work include/linux/task_work.h:40 [inline]
                     do_exit+0x70f/0x23c0 kernel/exit.c:976
                     do_group_exit+0x21b/0x2d0 kernel/exit.c:1118
                     get_signal+0x1284/0x1330 kernel/signal.c:3034
                     arch_do_signal_or_restart+0xbc/0x830 arch/x86/kernel/signal.c:337
                     __exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
                     exit_to_user_mode_loop+0x86/0x480 kernel/entry/common.c:98
                     __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
                     syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
                     syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
                     do_syscall_64+0x32d/0xf80 arch/x86/entry/syscall_64.c:100
                     entry_SYSCALL_64_after_hwframe+0x77/0x7f
    INITIAL READ USE at:
                          lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
                          __raw_read_lock_irqsave include/linux/rwlock_api_smp.h:172 [inline]
                          _raw_read_lock_irqsave+0x48/0x60 kernel/locking/spinlock.c:236
                          kill_fasync_rcu fs/fcntl.c:1135 [inline]
                          kill_fasync+0x199/0x4d0 fs/fcntl.c:1159
                          tun_net_xmit+0x10bc/0x1620 drivers/net/tun.c:1074
                          __netdev_start_xmit include/linux/netdevice.h:5324 [inline]
                          netdev_start_xmit include/linux/netdevice.h:5333 [inline]
                          xmit_one net/core/dev.c:3871 [inline]
                          dev_hard_start_xmit+0x2d8/0x870 net/core/dev.c:3887
                          sch_direct_xmit+0x251/0x4c0 net/sched/sch_generic.c:347
                          __dev_xmit_skb net/core/dev.c:4186 [inline]
                          __dev_queue_xmit+0x1550/0x3890 net/core/dev.c:4802
                          NF_HOOK_COND include/linux/netfilter.h:307 [inline]
                          ip6_output+0x340/0x550 net/ipv6/ip6_output.c:246
                          dst_output include/net/dst.h:470 [inline]
                          NF_HOOK include/linux/netfilter.h:318 [inline]
                          ndisc_send_skb+0xd0b/0x1670 net/ipv6/ndisc.c:512
                          addrconf_dad_completed+0x909/0xe60 net/ipv6/addrconf.c:4364
                          addrconf_dad_work+0xc5e/0x14c0 net/ipv6/addrconf.c:-1
                          process_one_work kernel/workqueue.c:3276 [inline]
                          process_scheduled_works+0xb6e/0x18c0 kernel/workqueue.c:3359
                          worker_thread+0xa53/0xfc0 kernel/workqueue.c:3440
                          kthread+0x388/0x470 kernel/kthread.c:436
                          ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
                          ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
  }
  ... key      at: [<ffffffff9a2ec200>] fasync_insert_entry.__key+0x0/0x20
  ... acquired at:
   __raw_read_lock_irqsave include/linux/rwlock_api_smp.h:172 [inline]
   _raw_read_lock_irqsave+0x48/0x60 kernel/locking/spinlock.c:236
   kill_fasync_rcu fs/fcntl.c:1135 [inline]
   kill_fasync+0x199/0x4d0 fs/fcntl.c:1159
   __pass_event drivers/input/evdev.c:240 [inline]
   evdev_pass_values+0x627/0xbd0 drivers/input/evdev.c:278
   evdev_events+0x1e6/0x340 drivers/input/evdev.c:306
   input_pass_values+0x288/0x890 drivers/input/input.c:128
   input_event_dispose+0x330/0x6b0 drivers/input/input.c:342
   input_inject_event+0x1dd/0x340 drivers/input/input.c:424
   evdev_write+0x325/0x4c0 drivers/input/evdev.c:528
   vfs_write+0x29a/0xb90 fs/read_write.c:686
   ksys_write+0x150/0x270 fs/read_write.c:740
   do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
   do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
   entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> (&f_owner->lock){....}-{3:3} {
   INITIAL USE at:
                   lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
                   __raw_write_lock_irq include/linux/rwlock_api_smp.h:211 [inline]
                   _raw_write_lock_irq+0x3d/0x50 kernel/locking/spinlock.c:326
                   __f_setown+0x67/0x370 fs/fcntl.c:136
                   tun_chr_fasync+0x127/0x1a0 drivers/net/tun.c:3384
                   setfl fs/fcntl.c:76 [inline]
                   do_fcntl+0x1201/0x1a20 fs/fcntl.c:477
                   __do_sys_fcntl fs/fcntl.c:602 [inline]
                   __se_sys_fcntl+0xc8/0x150 fs/fcntl.c:587
                   do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
                   do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
                   entry_SYSCALL_64_after_hwframe+0x77/0x7f
   INITIAL READ USE at:
                        lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
                        __raw_read_lock_irqsave include/linux/rwlock_api_smp.h:172 [inline]
                        _raw_read_lock_irqsave+0x48/0x60 kernel/locking/spinlock.c:236
                        send_sigio+0x38/0x370 fs/fcntl.c:918
                        kill_fasync_rcu fs/fcntl.c:1144 [inline]
                        kill_fasync+0x24d/0x4d0 fs/fcntl.c:1159
                        tun_net_xmit+0x10bc/0x1620 drivers/net/tun.c:1074
                        __netdev_start_xmit include/linux/netdevice.h:5324 [inline]
                        netdev_start_xmit include/linux/netdevice.h:5333 [inline]
                        xmit_one net/core/dev.c:3871 [inline]
                        dev_hard_start_xmit+0x2d8/0x870 net/core/dev.c:3887
                        sch_direct_xmit+0x251/0x4c0 net/sched/sch_generic.c:347
                        __dev_xmit_skb net/core/dev.c:4186 [inline]
                        __dev_queue_xmit+0x1550/0x3890 net/core/dev.c:4802
                        NF_HOOK_COND include/linux/netfilter.h:307 [inline]
                        ip6_output+0x340/0x550 net/ipv6/ip6_output.c:246
                        dst_output include/net/dst.h:470 [inline]
                        NF_HOOK include/linux/netfilter.h:318 [inline]
                        ndisc_send_skb+0xd0b/0x1670 net/ipv6/ndisc.c:512
                        addrconf_dad_completed+0x909/0xe60 net/ipv6/addrconf.c:4364
                        addrconf_dad_work+0xc5e/0x14c0 net/ipv6/addrconf.c:-1
                        process_one_work kernel/workqueue.c:3276 [inline]
                        process_scheduled_works+0xb6e/0x18c0 kernel/workqueue.c:3359
                        worker_thread+0xa53/0xfc0 kernel/workqueue.c:3440
                        kthread+0x388/0x470 kernel/kthread.c:436
                        ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
                        ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 }
 ... key      at: [<ffffffff9a2ec1e0>] file_f_owner_allocate.__key+0x0/0x20
 ... acquired at:
   __raw_read_lock_irqsave include/linux/rwlock_api_smp.h:172 [inline]
   _raw_read_lock_irqsave+0x48/0x60 kernel/locking/spinlock.c:236
   send_sigio+0x38/0x370 fs/fcntl.c:918
   kill_fasync_rcu fs/fcntl.c:1144 [inline]
   kill_fasync+0x24d/0x4d0 fs/fcntl.c:1159
   tun_net_xmit+0x10bc/0x1620 drivers/net/tun.c:1074
   __netdev_start_xmit include/linux/netdevice.h:5324 [inline]
   netdev_start_xmit include/linux/netdevice.h:5333 [inline]
   xmit_one net/core/dev.c:3871 [inline]
   dev_hard_start_xmit+0x2d8/0x870 net/core/dev.c:3887
   sch_direct_xmit+0x251/0x4c0 net/sched/sch_generic.c:347
   __dev_xmit_skb net/core/dev.c:4186 [inline]
   __dev_queue_xmit+0x1550/0x3890 net/core/dev.c:4802
   NF_HOOK_COND include/linux/netfilter.h:307 [inline]
   ip6_output+0x340/0x550 net/ipv6/ip6_output.c:246
   dst_output include/net/dst.h:470 [inline]
   NF_HOOK include/linux/netfilter.h:318 [inline]
   ndisc_send_skb+0xd0b/0x1670 net/ipv6/ndisc.c:512
   addrconf_dad_completed+0x909/0xe60 net/ipv6/addrconf.c:4364
   addrconf_dad_work+0xc5e/0x14c0 net/ipv6/addrconf.c:-1
   process_one_work kernel/workqueue.c:3276 [inline]
   process_scheduled_works+0xb6e/0x18c0 kernel/workqueue.c:3359
   worker_thread+0xa53/0xfc0 kernel/workqueue.c:3440
   kthread+0x388/0x470 kernel/kthread.c:436
   ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
   ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245


the dependencies between the lock to be acquired
 and SOFTIRQ-irq-unsafe lock:
-> (tasklist_lock){.+.+}-{3:3} {
   HARDIRQ-ON-R at:
                    lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
                    __raw_read_lock include/linux/rwlock_api_smp.h:161 [inline]
                    _raw_read_lock+0x36/0x50 kernel/locking/spinlock.c:228
                    __do_wait+0xde/0x740 kernel/exit.c:1678
                    do_wait+0x1e7/0x540 kernel/exit.c:1722
                    kernel_wait+0xd6/0x1c0 kernel/exit.c:1898
                    call_usermodehelper_exec_sync kernel/umh.c:136 [inline]
                    call_usermodehelper_exec_work+0xbe/0x230 kernel/umh.c:163
                    process_one_work kernel/workqueue.c:3276 [inline]
                    process_scheduled_works+0xb6e/0x18c0 kernel/workqueue.c:3359
                    worker_thread+0xa53/0xfc0 kernel/workqueue.c:3440
                    kthread+0x388/0x470 kernel/kthread.c:436
                    ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
                    ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
   SOFTIRQ-ON-R at:
                    lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
                    __raw_read_lock include/linux/rwlock_api_smp.h:161 [inline]
                    _raw_read_lock+0x36/0x50 kernel/locking/spinlock.c:228
                    __do_wait+0xde/0x740 kernel/exit.c:1678
                    do_wait+0x1e7/0x540 kernel/exit.c:1722
                    kernel_wait+0xd6/0x1c0 kernel/exit.c:1898
                    call_usermodehelper_exec_sync kernel/umh.c:136 [inline]
                    call_usermodehelper_exec_work+0xbe/0x230 kernel/umh.c:163
                    process_one_work kernel/workqueue.c:3276 [inline]
                    process_scheduled_works+0xb6e/0x18c0 kernel/workqueue.c:3359
                    worker_thread+0xa53/0xfc0 kernel/workqueue.c:3440
                    kthread+0x388/0x470 kernel/kthread.c:436
                    ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
                    ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
   INITIAL USE at:
                   lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
                   __raw_write_lock_irq include/linux/rwlock_api_smp.h:211 [inline]
                   _raw_write_lock_irq+0x3d/0x50 kernel/locking/spinlock.c:326
                   copy_process+0x247a/0x3cd0 kernel/fork.c:2369
                   kernel_clone+0x248/0x8e0 kernel/fork.c:2653
                   user_mode_thread+0x110/0x180 kernel/fork.c:2729
                   rest_init+0x23/0x300 init/main.c:725
                   start_kernel+0x385/0x3d0 init/main.c:1210
                   x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310
                   x86_64_start_kernel+0x143/0x1c0 arch/x86/kernel/head64.c:291
                   common_startup_64+0x13e/0x147
   INITIAL READ USE at:
                        lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
                        __raw_read_lock include/linux/rwlock_api_smp.h:161 [inline]
                        _raw_read_lock+0x36/0x50 kernel/locking/spinlock.c:228
                        __do_wait+0xde/0x740 kernel/exit.c:1678
                        do_wait+0x1e7/0x540 kernel/exit.c:1722
                        kernel_wait+0xd6/0x1c0 kernel/exit.c:1898
                        call_usermodehelper_exec_sync kernel/umh.c:136 [inline]
                        call_usermodehelper_exec_work+0xbe/0x230 kernel/umh.c:163
                        process_one_work kernel/workqueue.c:3276 [inline]
                        process_scheduled_works+0xb6e/0x18c0 kernel/workqueue.c:3359
                        worker_thread+0xa53/0xfc0 kernel/workqueue.c:3440
                        kthread+0x388/0x470 kernel/kthread.c:436
                        ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
                        ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 }
 ... key      at: [<ffffffff8e40c058>] tasklist_lock+0x18/0x40
 ... acquired at:
   __raw_read_lock include/linux/rwlock_api_smp.h:161 [inline]
   _raw_read_lock+0x36/0x50 kernel/locking/spinlock.c:228
   send_sigurg+0x12b/0x420 fs/fcntl.c:978
   sk_send_sigurg+0x6c/0x2e0 net/core/sock.c:3669
   queue_oob+0x42c/0x4f0 net/unix/af_unix.c:2352
   unix_stream_sendmsg+0xcb1/0xe80 net/unix/af_unix.c:2486
   sock_sendmsg_nosec net/socket.c:727 [inline]
   __sock_sendmsg net/socket.c:742 [inline]
   ____sys_sendmsg+0x972/0x9f0 net/socket.c:2592
   ___sys_sendmsg+0x2a5/0x360 net/socket.c:2646
   __sys_sendmmsg+0x27c/0x4e0 net/socket.c:2735
   __do_sys_sendmmsg net/socket.c:2762 [inline]
   __se_sys_sendmmsg net/socket.c:2759 [inline]
   __x64_sys_sendmmsg+0xa0/0xc0 net/socket.c:2759
   do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
   do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
   entry_SYSCALL_64_after_hwframe+0x77/0x7f


stack backtrace:
CPU: 0 UID: 0 PID: 6651 Comm: syz.7.8974 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_bad_irq_dependency kernel/locking/lockdep.c:2616 [inline]
 check_irq_usage kernel/locking/lockdep.c:2857 [inline]
 check_prev_add kernel/locking/lockdep.c:3169 [inline]
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x2a94/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
 __raw_read_lock include/linux/rwlock_api_smp.h:161 [inline]
 _raw_read_lock+0x36/0x50 kernel/locking/spinlock.c:228
 send_sigurg+0x12b/0x420 fs/fcntl.c:978
 sk_send_sigurg+0x6c/0x2e0 net/core/sock.c:3669
 queue_oob+0x42c/0x4f0 net/unix/af_unix.c:2352
 unix_stream_sendmsg+0xcb1/0xe80 net/unix/af_unix.c:2486
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0x972/0x9f0 net/socket.c:2592
 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2646
 __sys_sendmmsg+0x27c/0x4e0 net/socket.c:2735
 __do_sys_sendmmsg net/socket.c:2762 [inline]
 __se_sys_sendmmsg net/socket.c:2759 [inline]
 __x64_sys_sendmmsg+0xa0/0xc0 net/socket.c:2759
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f929959c799
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:00007f929a4c1028 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007f9299815fa0 RCX: 00007f929959c799
RDX: 0000000000000001 RSI: 0000200000006c40 RDI: 0000000000000006
RBP: 00007f9299632c99 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000040015 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9299816038 R14: 00007f9299815fa0 R15: 00007f929993fa48
 </TASK>