========================================================
WARNING: possible irq lock inversion dependency detected
5.6.0-syzkaller #0 Not tainted
--------------------------------------------------------
ksoftirqd/0/9 just changed the state of lock:
ffffffff898090d8 (tasklist_lock){.+.?}-{2:2}, at: send_sigurg+0x9f/0x320 fs/fcntl.c:840
but this lock took another, SOFTIRQ-unsafe lock in the past:
 (&pid->wait_pidfd){+.+.}-{2:2}


and interrupts could create inverse lock ordering between them.


other info that might help us debug this:
 Possible interrupt unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&pid->wait_pidfd);
                               local_irq_disable();
                               lock(tasklist_lock);
                               lock(&pid->wait_pidfd);
  <Interrupt>
    lock(tasklist_lock);

 *** DEADLOCK ***

4 locks held by ksoftirqd/0/9:
 #0: ffffffff899bbbc0 (rcu_read_lock){....}-{1:2}, at: __write_once_size include/linux/compiler.h:226 [inline]
 #0: ffffffff899bbbc0 (rcu_read_lock){....}-{1:2}, at: __skb_unlink include/linux/skbuff.h:2078 [inline]
 #0: ffffffff899bbbc0 (rcu_read_lock){....}-{1:2}, at: __skb_dequeue include/linux/skbuff.h:2093 [inline]
 #0: ffffffff899bbbc0 (rcu_read_lock){....}-{1:2}, at: process_backlog+0x1ad/0x7a0 net/core/dev.c:6131
 #1: ffffffff899bbbc0 (rcu_read_lock){....}-{1:2}, at: __skb_pull include/linux/skbuff.h:2309 [inline]
 #1: ffffffff899bbbc0 (rcu_read_lock){....}-{1:2}, at: ip_local_deliver_finish+0x124/0x360 net/ipv4/ip_input.c:228
 #2: ffff8880a1d1e120 (slock-AF_INET/1){+.-.}-{2:2}, at: tcp_v4_rcv+0x2d09/0x39c0 net/ipv4/tcp_ipv4.c:1997
 #3: ffff8880949e6478 (&f->f_owner.lock){.+.?}-{2:2}, at: send_sigurg+0x1a/0x320 fs/fcntl.c:824

the shortest dependencies between 2nd lock and 1st lock:
 -> (&pid->wait_pidfd){+.+.}-{2:2} {
    HARDIRQ-ON-W at:
                      lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
                      __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
                      _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
                      spin_lock include/linux/spinlock.h:353 [inline]
                      proc_pid_make_inode+0x1f9/0x3c0 fs/proc/base.c:1880
                      proc_pid_instantiate+0x51/0x150 fs/proc/base.c:3285
                      proc_pid_lookup+0x1da/0x340 fs/proc/base.c:3320
                      proc_root_lookup+0x20/0x60 fs/proc/root.c:243
                      __lookup_slow+0x256/0x490 fs/namei.c:1530
                      lookup_slow fs/namei.c:1547 [inline]
                      walk_component+0x418/0x6a0 fs/namei.c:1846
                      link_path_walk.part.0+0x4f1/0xb50 fs/namei.c:2166
                      link_path_walk fs/namei.c:2098 [inline]
                      path_openat+0x25a/0x27d0 fs/namei.c:3342
                      do_filp_open+0x192/0x260 fs/namei.c:3373
                      do_sys_openat2+0x585/0x7d0 fs/open.c:1148
                      do_sys_open+0xc3/0x140 fs/open.c:1164
                      do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
                      entry_SYSCALL_64_after_hwframe+0x49/0xb3
    SOFTIRQ-ON-W at:
                      lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
                      __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
                      _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
                      spin_lock include/linux/spinlock.h:353 [inline]
                      proc_pid_make_inode+0x1f9/0x3c0 fs/proc/base.c:1880
                      proc_pid_instantiate+0x51/0x150 fs/proc/base.c:3285
                      proc_pid_lookup+0x1da/0x340 fs/proc/base.c:3320
                      proc_root_lookup+0x20/0x60 fs/proc/root.c:243
                      __lookup_slow+0x256/0x490 fs/namei.c:1530
                      lookup_slow fs/namei.c:1547 [inline]
                      walk_component+0x418/0x6a0 fs/namei.c:1846
                      link_path_walk.part.0+0x4f1/0xb50 fs/namei.c:2166
                      link_path_walk fs/namei.c:2098 [inline]
                      path_openat+0x25a/0x27d0 fs/namei.c:3342
                      do_filp_open+0x192/0x260 fs/namei.c:3373
                      do_sys_openat2+0x585/0x7d0 fs/open.c:1148
                      do_sys_open+0xc3/0x140 fs/open.c:1164
                      do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
                      entry_SYSCALL_64_after_hwframe+0x49/0xb3
    INITIAL USE at:
                     lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
                     __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
                     _raw_spin_lock_irqsave+0x8c/0xbf kernel/locking/spinlock.c:159
                     __wake_up_common_lock+0xb4/0x130 kernel/sched/wait.c:122
                     do_notify_pidfd kernel/signal.c:1900 [inline]
                     do_notify_parent+0x19e/0xe60 kernel/signal.c:1927
                     exit_notify kernel/exit.c:660 [inline]
                     do_exit+0x238f/0x2dd0 kernel/exit.c:816
                     call_usermodehelper_exec_async+0x507/0x710 kernel/umh.c:125
                     ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
  }
  ... key      at: [<ffffffff8bbc0680>] __key.53827+0x0/0x40
  ... acquired at:
   __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
   _raw_spin_lock_irqsave+0x8c/0xbf kernel/locking/spinlock.c:159
   __wake_up_common_lock+0xb4/0x130 kernel/sched/wait.c:122
   do_notify_pidfd kernel/signal.c:1900 [inline]
   do_notify_parent+0x19e/0xe60 kernel/signal.c:1927
   exit_notify kernel/exit.c:660 [inline]
   do_exit+0x238f/0x2dd0 kernel/exit.c:816
   call_usermodehelper_exec_async+0x507/0x710 kernel/umh.c:125
   ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

-> (tasklist_lock){.+.?}-{2:2} {
   HARDIRQ-ON-R at:
                    lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
                    __raw_read_lock include/linux/rwlock_api_smp.h:149 [inline]
                    _raw_read_lock+0x2d/0x40 kernel/locking/spinlock.c:223
                    do_wait+0x3b9/0xa00 kernel/exit.c:1436
                    kernel_wait4+0x14c/0x260 kernel/exit.c:1611
                    call_usermodehelper_exec_sync kernel/umh.c:150 [inline]
                    call_usermodehelper_exec_work+0x172/0x260 kernel/umh.c:187
                    process_one_work+0x965/0x16a0 kernel/workqueue.c:2266
                    worker_thread+0x96/0xe20 kernel/workqueue.c:2412
                    kthread+0x388/0x470 kernel/kthread.c:268
                    ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
   IN-SOFTIRQ-R at:
                    lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
                    __raw_read_lock include/linux/rwlock_api_smp.h:149 [inline]
                    _raw_read_lock+0x2d/0x40 kernel/locking/spinlock.c:223
                    send_sigurg+0x9f/0x320 fs/fcntl.c:840
                    sk_send_sigurg+0x76/0x300 net/core/sock.c:2855
                    tcp_check_urg net/ipv4/tcp_input.c:5353 [inline]
                    tcp_urg+0x38c/0xb80 net/ipv4/tcp_input.c:5394
                    tcp_rcv_established+0x8f3/0x1d90 net/ipv4/tcp_input.c:5724
                    tcp_v4_do_rcv+0x605/0x8b0 net/ipv4/tcp_ipv4.c:1621
                    tcp_v4_rcv+0x2f60/0x39c0 net/ipv4/tcp_ipv4.c:2003
                    ip_protocol_deliver_rcu+0x57/0x880 net/ipv4/ip_input.c:204
                    ip_local_deliver_finish+0x220/0x360 net/ipv4/ip_input.c:231
                    NF_HOOK include/linux/netfilter.h:307 [inline]
                    NF_HOOK include/linux/netfilter.h:301 [inline]
                    ip_local_deliver+0x1c8/0x4e0 net/ipv4/ip_input.c:252
                    dst_input include/net/dst.h:441 [inline]
                    ip_rcv_finish+0x1da/0x2f0 net/ipv4/ip_input.c:428
                    NF_HOOK include/linux/netfilter.h:307 [inline]
                    NF_HOOK include/linux/netfilter.h:301 [inline]
                    ip_rcv+0xd0/0x3c0 net/ipv4/ip_input.c:539
                    __netif_receive_skb_one_core+0xf5/0x160 net/core/dev.c:5187
                    __netif_receive_skb+0x27/0x1c0 net/core/dev.c:5301
                    process_backlog+0x21e/0x7a0 net/core/dev.c:6133
                    napi_poll net/core/dev.c:6571 [inline]
                    net_rx_action+0x4c2/0x1070 net/core/dev.c:6639
                    __do_softirq+0x26c/0x9f7 kernel/softirq.c:292
                    run_ksoftirqd kernel/softirq.c:604 [inline]
                    run_ksoftirqd+0x89/0x100 kernel/softirq.c:596
                    smpboot_thread_fn+0x653/0x9e0 kernel/smpboot.c:165
                    kthread+0x388/0x470 kernel/kthread.c:268
                    ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
   SOFTIRQ-ON-R at:
                    lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
                    __raw_read_lock include/linux/rwlock_api_smp.h:149 [inline]
                    _raw_read_lock+0x2d/0x40 kernel/locking/spinlock.c:223
                    do_wait+0x3b9/0xa00 kernel/exit.c:1436
                    kernel_wait4+0x14c/0x260 kernel/exit.c:1611
                    call_usermodehelper_exec_sync kernel/umh.c:150 [inline]
                    call_usermodehelper_exec_work+0x172/0x260 kernel/umh.c:187
                    process_one_work+0x965/0x16a0 kernel/workqueue.c:2266
                    worker_thread+0x96/0xe20 kernel/workqueue.c:2412
                    kthread+0x388/0x470 kernel/kthread.c:268
                    ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
   INITIAL USE at:
                   lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
                   __raw_write_lock_irq include/linux/rwlock_api_smp.h:196 [inline]
                   _raw_write_lock_irq+0x5b/0x80 kernel/locking/spinlock.c:311
                   copy_process+0x3322/0x7110 kernel/fork.c:2206
                   _do_fork+0x12d/0x1010 kernel/fork.c:2430
                   kernel_thread+0xb8/0xf0 kernel/fork.c:2517
                   rest_init+0x23/0x365 init/main.c:632
                   start_kernel+0x867/0x8a1 init/main.c:1004
                   secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:242
 }
 ... key      at: [<ffffffff898090d8>] tasklist_lock+0x18/0x40
 ... acquired at:
   mark_lock_irq kernel/locking/lockdep.c:3585 [inline]
   mark_lock+0x624/0xf10 kernel/locking/lockdep.c:3935
   mark_usage kernel/locking/lockdep.c:3826 [inline]
   __lock_acquire+0x1ed9/0x4e00 kernel/locking/lockdep.c:4298
   lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
   __raw_read_lock include/linux/rwlock_api_smp.h:149 [inline]
   _raw_read_lock+0x2d/0x40 kernel/locking/spinlock.c:223
   send_sigurg+0x9f/0x320 fs/fcntl.c:840
   sk_send_sigurg+0x76/0x300 net/core/sock.c:2855
   tcp_check_urg net/ipv4/tcp_input.c:5353 [inline]
   tcp_urg+0x38c/0xb80 net/ipv4/tcp_input.c:5394
   tcp_rcv_established+0x8f3/0x1d90 net/ipv4/tcp_input.c:5724
   tcp_v4_do_rcv+0x605/0x8b0 net/ipv4/tcp_ipv4.c:1621
   tcp_v4_rcv+0x2f60/0x39c0 net/ipv4/tcp_ipv4.c:2003
   ip_protocol_deliver_rcu+0x57/0x880 net/ipv4/ip_input.c:204
   ip_local_deliver_finish+0x220/0x360 net/ipv4/ip_input.c:231
   NF_HOOK include/linux/netfilter.h:307 [inline]
   NF_HOOK include/linux/netfilter.h:301 [inline]
   ip_local_deliver+0x1c8/0x4e0 net/ipv4/ip_input.c:252
   dst_input include/net/dst.h:441 [inline]
   ip_rcv_finish+0x1da/0x2f0 net/ipv4/ip_input.c:428
   NF_HOOK include/linux/netfilter.h:307 [inline]
   NF_HOOK include/linux/netfilter.h:301 [inline]
   ip_rcv+0xd0/0x3c0 net/ipv4/ip_input.c:539
   __netif_receive_skb_one_core+0xf5/0x160 net/core/dev.c:5187
   __netif_receive_skb+0x27/0x1c0 net/core/dev.c:5301
   process_backlog+0x21e/0x7a0 net/core/dev.c:6133
   napi_poll net/core/dev.c:6571 [inline]
   net_rx_action+0x4c2/0x1070 net/core/dev.c:6639
   __do_softirq+0x26c/0x9f7 kernel/softirq.c:292
   run_ksoftirqd kernel/softirq.c:604 [inline]
   run_ksoftirqd+0x89/0x100 kernel/softirq.c:596
   smpboot_thread_fn+0x653/0x9e0 kernel/smpboot.c:165
   kthread+0x388/0x470 kernel/kthread.c:268
   ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352


stack backtrace:
CPU: 0 PID: 9 Comm: ksoftirqd/0 Not tainted 5.6.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x188/0x20d lib/dump_stack.c:118
 print_irq_inversion_bug kernel/locking/lockdep.c:3448 [inline]
 check_usage_forwards.cold+0x20/0x29 kernel/locking/lockdep.c:3472
 mark_lock_irq kernel/locking/lockdep.c:3585 [inline]
 mark_lock+0x624/0xf10 kernel/locking/lockdep.c:3935
 mark_usage kernel/locking/lockdep.c:3826 [inline]
 __lock_acquire+0x1ed9/0x4e00 kernel/locking/lockdep.c:4298
 lock_acquire+0x1f2/0x8f0 kernel/locking/lockdep.c:4923
 __raw_read_lock include/linux/rwlock_api_smp.h:149 [inline]
 _raw_read_lock+0x2d/0x40 kernel/locking/spinlock.c:223
 send_sigurg+0x9f/0x320 fs/fcntl.c:840
 sk_send_sigurg+0x76/0x300 net/core/sock.c:2855
 tcp_check_urg net/ipv4/tcp_input.c:5353 [inline]
 tcp_urg+0x38c/0xb80 net/ipv4/tcp_input.c:5394
 tcp_rcv_established+0x8f3/0x1d90 net/ipv4/tcp_input.c:5724
 tcp_v4_do_rcv+0x605/0x8b0 net/ipv4/tcp_ipv4.c:1621
 tcp_v4_rcv+0x2f60/0x39c0 net/ipv4/tcp_ipv4.c:2003
 ip_protocol_deliver_rcu+0x57/0x880 net/ipv4/ip_input.c:204
 ip_local_deliver_finish+0x220/0x360 net/ipv4/ip_input.c:231
 NF_HOOK include/linux/netfilter.h:307 [inline]
 NF_HOOK include/linux/netfilter.h:301 [inline]
 ip_local_deliver+0x1c8/0x4e0 net/ipv4/ip_input.c:252
 dst_input include/net/dst.h:441 [inline]
 ip_rcv_finish+0x1da/0x2f0 net/ipv4/ip_input.c:428
 NF_HOOK include/linux/netfilter.h:307 [inline]
 NF_HOOK include/linux/netfilter.h:301 [inline]
 ip_rcv+0xd0/0x3c0 net/ipv4/ip_input.c:539
 __netif_receive_skb_one_core+0xf5/0x160 net/core/dev.c:5187
 __netif_receive_skb+0x27/0x1c0 net/core/dev.c:5301
 process_backlog+0x21e/0x7a0 net/core/dev.c:6133
 napi_poll net/core/dev.c:6571 [inline]
 net_rx_action+0x4c2/0x1070 net/core/dev.c:6639
 __do_softirq+0x26c/0x9f7 kernel/softirq.c:292
 run_ksoftirqd kernel/softirq.c:604 [inline]
 run_ksoftirqd+0x89/0x100 kernel/softirq.c:596
 smpboot_thread_fn+0x653/0x9e0 kernel/smpboot.c:165
 kthread+0x388/0x470 kernel/kthread.c:268
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352