================================
WARNING: inconsistent lock state
syzkaller #0 Not tainted
--------------------------------
inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
ksoftirqd/0/15 [HC0[0]:SC1[1]:HE1:SE0] takes:
ffff88802c938260 (sk_lock-AF_X25){+.?.}-{0:0}, at: lock_sock include/net/sock.h:1713 [inline]
ffff88802c938260 (sk_lock-AF_X25){+.?.}-{0:0}, at: x25_kill_by_neigh+0x168/0x280 net/x25/af_x25.c:1778
{SOFTIRQ-ON-W} state was registered at:
  lock_acquire kernel/locking/lockdep.c:5942 [inline]
  lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
  lock_sock_nested+0x41/0xf0 net/core/sock.c:3837
  lock_sock include/net/sock.h:1713 [inline]
  x25_bind+0x221/0x5c0 net/x25/af_x25.c:694
  __sys_bind_socket net/socket.c:1945 [inline]
  __sys_bind_socket net/socket.c:1937 [inline]
  __sys_bind+0x1a9/0x260 net/socket.c:1976
  __do_sys_bind net/socket.c:1981 [inline]
  __se_sys_bind net/socket.c:1979 [inline]
  __x64_sys_bind+0x72/0xb0 net/socket.c:1979
  do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
  do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
  entry_SYSCALL_64_after_hwframe+0x77/0x7f
irq event stamp: 357794
hardirqs last  enabled at (357794): [<ffffffff81ca5245>] __local_bh_enable_ip+0xa5/0x120 kernel/softirq.c:478
hardirqs last disabled at (357793): [<ffffffff81ca526e>] __local_bh_enable_ip+0xce/0x120 kernel/softirq.c:455
softirqs last  enabled at (357466): [<ffffffff81ca4d98>] run_ksoftirqd kernel/softirq.c:1099 [inline]
softirqs last  enabled at (357466): [<ffffffff81ca4d98>] run_ksoftirqd+0x38/0x60 kernel/softirq.c:1091
softirqs last disabled at (357471): [<ffffffff81ca4d98>] run_ksoftirqd kernel/softirq.c:1099 [inline]
softirqs last disabled at (357471): [<ffffffff81ca4d98>] run_ksoftirqd+0x38/0x60 kernel/softirq.c:1091

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

       CPU0
       ----
  lock(sk_lock-AF_X25);
  <Interrupt>
    lock(sk_lock-AF_X25);

 *** DEADLOCK ***

locks held by ksoftirqd/0/15: 1, last CPU#0:
 #0: ffffffff8edec5a0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #0: ffffffff8edec5a0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #0: ffffffff8edec5a0 (rcu_read_lock){....}-{1:3}, at: netif_receive_skb_core+0x25/0x1a0 net/core/dev.c:6321

stack backtrace:
CPU: 0 UID: 0 PID: 15 Comm: ksoftirqd/0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_usage_bug.part.0+0x258/0x340 kernel/locking/lockdep.c:4086
 print_usage_bug kernel/locking/lockdep.c:4054 [inline]
 valid_state kernel/locking/lockdep.c:4100 [inline]
 mark_lock_irq kernel/locking/lockdep.c:4311 [inline]
 mark_lock+0x956/0x1020 kernel/locking/lockdep.c:4797
 mark_usage kernel/locking/lockdep.c:4686 [inline]
 __lock_acquire+0x7f1/0x1f40 kernel/locking/lockdep.c:5242
 lock_acquire kernel/locking/lockdep.c:5942 [inline]
 lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
 lock_sock_nested+0x41/0xf0 net/core/sock.c:3837
 lock_sock include/net/sock.h:1713 [inline]
 x25_kill_by_neigh+0x168/0x280 net/x25/af_x25.c:1778
 x25_lapb_receive_frame+0x4b1/0x1000 net/x25/x25_dev.c:138
 __netif_receive_skb_one_core+0x1b2/0x1e0 net/core/dev.c:6297
 netif_receive_skb_core+0x5a/0x1a0 net/core/dev.c:6322
 lapbeth_napi_poll+0x42/0xc0 drivers/net/wan/lapbether.c:100
 __napi_poll.constprop.0+0xaf/0x450 net/core/dev.c:7830
 napi_poll net/core/dev.c:7893 [inline]
 net_rx_action+0xa40/0xf20 net/core/dev.c:8050
 handle_softirqs+0x1e6/0x9d0 kernel/softirq.c:645
 run_ksoftirqd kernel/softirq.c:1099 [inline]
 run_ksoftirqd+0x38/0x60 kernel/softirq.c:1091
 smpboot_thread_fn+0x3d3/0xab0 kernel/smpboot.c:160
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
BUG: sleeping function called from invalid context at net/core/sock.c:3839
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 15, name: ksoftirqd/0
preempt_count: 100, expected: 0
RCU nest depth: 1, expected: 0
INFO: lockdep is turned off.
Preemption disabled at:
[<ffffffff81ca41d3>] softirq_handle_begin kernel/softirq.c:486 [inline]
[<ffffffff81ca41d3>] handle_softirqs+0xf3/0x9d0 kernel/softirq.c:621
CPU: 0 UID: 0 PID: 15 Comm: ksoftirqd/0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 __might_resched.cold+0x1dc/0x222 kernel/sched/core.c:9264
 lock_sock_nested+0x52/0xf0 net/core/sock.c:3839
 lock_sock include/net/sock.h:1713 [inline]
 x25_kill_by_neigh+0x168/0x280 net/x25/af_x25.c:1778
 x25_lapb_receive_frame+0x4b1/0x1000 net/x25/x25_dev.c:138
 __netif_receive_skb_one_core+0x1b2/0x1e0 net/core/dev.c:6297
 netif_receive_skb_core+0x5a/0x1a0 net/core/dev.c:6322
 lapbeth_napi_poll+0x42/0xc0 drivers/net/wan/lapbether.c:100
 __napi_poll.constprop.0+0xaf/0x450 net/core/dev.c:7830
 napi_poll net/core/dev.c:7893 [inline]
 net_rx_action+0xa40/0xf20 net/core/dev.c:8050
 handle_softirqs+0x1e6/0x9d0 kernel/softirq.c:645
 run_ksoftirqd kernel/softirq.c:1099 [inline]
 run_ksoftirqd+0x38/0x60 kernel/softirq.c:1091
 smpboot_thread_fn+0x3d3/0xab0 kernel/smpboot.c:160
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>