syzbot

INFO: rcu_preempt self-detected stall on CPU
	1-...: (10499 ticks this GP) idle=1c6/140000000000001/0 softirq=51252/51252 fqs=0 
	 (t=10500 jiffies g=14827 c=14826 q=49)
rcu_preempt kthread starved for 10500 jiffies! g14827 c14826 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x402 ->cpu=0
rcu_preempt     I29920     8      2 0x80000000
Call Trace:
 schedule+0x8d/0x1b0 kernel/sched/core.c:3428
 schedule_timeout+0x43c/0xe40 kernel/time/timer.c:1746
 rcu_gp_kthread+0xb8e/0x1ce0 kernel/rcu/tree.c:2255
 kthread+0x30d/0x420 kernel/kthread.c:232
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404
NMI backtrace for cpu 1
CPU: 1 PID: 22983 Comm: syz-executor.2 Not tainted 4.14.180-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x13e/0x194 lib/dump_stack.c:58
 nmi_cpu_backtrace.cold+0x57/0x93 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x139/0x17e lib/nmi_backtrace.c:62
 trigger_single_cpu_backtrace include/linux/nmi.h:158 [inline]
 rcu_dump_cpu_stacks+0x16d/0x1b8 kernel/rcu/tree.c:1396
 print_cpu_stall kernel/rcu/tree.c:1542 [inline]
 check_cpu_stall kernel/rcu/tree.c:1610 [inline]
 __rcu_pending kernel/rcu/tree.c:3390 [inline]
 rcu_pending kernel/rcu/tree.c:3452 [inline]
 rcu_check_callbacks.cold+0x490/0xdaa kernel/rcu/tree.c:2792
 update_process_times+0x29/0x60 kernel/time/timer.c:1590
 tick_sched_handle+0x7d/0x150 kernel/time/tick-sched.c:165
 tick_sched_timer+0x3e/0x120 kernel/time/tick-sched.c:1223
 __run_hrtimer kernel/time/hrtimer.c:1223 [inline]
 __hrtimer_run_queues+0x25c/0xbb0 kernel/time/hrtimer.c:1287
 hrtimer_interrupt+0x1e6/0x5e0 kernel/time/hrtimer.c:1321
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1075 [inline]
 smp_apic_timer_interrupt+0x117/0x5e0 arch/x86/kernel/apic/apic.c:1100
 apic_timer_interrupt+0x8f/0xa0 arch/x86/entry/entry_64.S:792
 </IRQ>
RIP: 0010:get_current arch/x86/include/asm/current.h:15 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x0/0x50 kernel/kcov.c:60
RSP: 0018:ffff8882155df228 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff10
RAX: 0000000000000003 RBX: 000000000000007f RCX: 0000000000001bc8
RDX: 0000000000040000 RSI: 0000000000000003 RDI: 0000000000000000
RBP: ffff8882154326e2 R08: 0000000000001f64 R09: ffffffff8a06f360
R10: ffff8880a4460c10 R11: ffff8880a44602c0 R12: ffff88805b85a1c0
R13: 0000000000000003 R14: ffff8882154326c8 R15: dffffc0000000000
 sfq_dequeue+0x125/0xdb0 net/sched/sch_sfq.c:497
 dequeue_skb net/sched/sch_generic.c:148 [inline]
 qdisc_restart net/sched/sch_generic.c:241 [inline]
 __qdisc_run+0x2b7/0xde0 net/sched/sch_generic.c:257
 __dev_xmit_skb net/core/dev.c:3223 [inline]
 __dev_queue_xmit+0x1b9b/0x25c0 net/core/dev.c:3493
 neigh_hh_output include/net/neighbour.h:490 [inline]
 neigh_output include/net/neighbour.h:498 [inline]
 ip_finish_output2+0xde8/0x14a0 net/ipv4/ip_output.c:229
 ip_finish_output+0x556/0xc30 net/ipv4/ip_output.c:317
 NF_HOOK_COND include/linux/netfilter.h:239 [inline]
 ip_output+0x1c2/0x520 net/ipv4/ip_output.c:405
 dst_output include/net/dst.h:462 [inline]
 ip_local_out+0x93/0x170 net/ipv4/ip_output.c:124
 ip_queue_xmit+0x7b2/0x1b20 net/ipv4/ip_output.c:504
 __tcp_transmit_skb+0x1654/0x2dd0 net/ipv4/tcp_output.c:1131
 __tcp_send_ack.part.0+0x3ab/0x5a0 net/ipv4/tcp_output.c:3640
 __tcp_send_ack net/ipv4/tcp_output.c:3646 [inline]
 tcp_send_ack+0x6f/0x90 net/ipv4/tcp_output.c:3646
 __tcp_ack_snd_check+0xf6/0x380 net/ipv4/tcp_input.c:5145
 tcp_ack_snd_check net/ipv4/tcp_input.c:5158 [inline]
 tcp_rcv_established+0x665/0x15d0 net/ipv4/tcp_input.c:5571
 tcp_v4_do_rcv+0x55d/0x7e0 net/ipv4/tcp_ipv4.c:1467
 sk_backlog_rcv include/net/sock.h:917 [inline]
 __release_sock+0x12a/0x350 net/core/sock.c:2267
 release_sock+0x54/0x1b0 net/core/sock.c:2782
 sk_stream_wait_memory+0x492/0xbf0 net/core/stream.c:145
 tcp_sendmsg_locked+0x1168/0x2fd0 net/ipv4/tcp.c:1416
 tcp_sendmsg+0x2b/0x40 net/ipv4/tcp.c:1457
 inet_sendmsg+0x116/0x4d0 net/ipv4/af_inet.c:762
 sock_sendmsg_nosec net/socket.c:646 [inline]
 sock_sendmsg+0xc5/0x100 net/socket.c:656
 SYSC_sendto+0x1c4/0x2b0 net/socket.c:1763
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45c829
RSP: 002b:00007f5a551acc78 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 0000000000500f60 RCX: 000000000045c829
RDX: 000000000000fe6a RSI: 00000000200012c0 RDI: 0000000000000004
RBP: 000000000078bf00 R08: 0000000000000000 R09: fffffffffffffe2b
R10: 000000000000000e R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000a0e R14: 00000000004ccc56 R15: 00007f5a551ad6d4