syzbot

INFO: rcu_sched self-detected stall on CPU
	0-...!: (124999 ticks this GP) idle=b22/1/4611686018427387906 softirq=93002/93002 fqs=22 
	 (t=125000 jiffies g=43980 c=43979 q=55)
rcu_sched kthread starved for 124912 jiffies! g43980 c43979 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x0 ->cpu=1
rcu_sched       R  running task    23448     8      2 0x80000000
Call Trace:
 context_switch kernel/sched/core.c:2862 [inline]
 __schedule+0x8fb/0x1ec0 kernel/sched/core.c:3440
 schedule+0xf5/0x430 kernel/sched/core.c:3499
 schedule_timeout+0x118/0x230 kernel/time/timer.c:1801
 rcu_gp_kthread+0x9dd/0x18e0 kernel/rcu/tree.c:2230
 kthread+0x33c/0x400 kernel/kthread.c:238
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:406
NMI backtrace for cpu 0
CPU: 0 PID: 6943 Comm: syz-executor3 Not tainted 4.16.0-rc4+ #256
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+0x194/0x24d lib/dump_stack.c:53
 nmi_cpu_backtrace+0x1d2/0x210 lib/nmi_backtrace.c:103
 nmi_trigger_cpumask_backtrace+0x123/0x180 lib/nmi_backtrace.c:62
 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 trigger_single_cpu_backtrace include/linux/nmi.h:156 [inline]
 rcu_dump_cpu_stacks+0x186/0x1de kernel/rcu/tree.c:1375
 print_cpu_stall kernel/rcu/tree.c:1524 [inline]
 check_cpu_stall.isra.61+0xbb8/0x15b0 kernel/rcu/tree.c:1592
 __rcu_pending kernel/rcu/tree.c:3361 [inline]
 rcu_pending kernel/rcu/tree.c:3423 [inline]
 rcu_check_callbacks+0x238/0xd20 kernel/rcu/tree.c:2763
 update_process_times+0x30/0x60 kernel/time/timer.c:1636
 tick_sched_handle+0x85/0x160 kernel/time/tick-sched.c:162
 tick_sched_timer+0x42/0x120 kernel/time/tick-sched.c:1194
 __run_hrtimer kernel/time/hrtimer.c:1349 [inline]
 __hrtimer_run_queues+0x39c/0xec0 kernel/time/hrtimer.c:1411
 hrtimer_interrupt+0x2a5/0x6f0 kernel/time/hrtimer.c:1469
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1025 [inline]
 smp_apic_timer_interrupt+0x14a/0x700 arch/x86/kernel/apic/apic.c:1050
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:857
 </IRQ>
RIP: 0010:__read_once_size include/linux/compiler.h:188 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x3b/0x50 kernel/kcov.c:106
RSP: 0018:ffff8801aad1f3a0 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff12
RAX: 0000000000010000 RBX: ffff8801ac534dc0 RCX: ffffffff84e64b6f
RDX: 000000000000ffff RSI: ffffc90004c71000 RDI: ffff8801d96e6d50
RBP: ffff8801aad1f3a0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801d96e6c00
R13: dffffc0000000000 R14: ffffed00358a69d7 R15: ffff8801ac534ebc
 xfrm_get_dst_nexthop net/xfrm/xfrm_policy.c:2729 [inline]
 xfrm_confirm_neigh+0x9f/0x270 net/xfrm/xfrm_policy.c:2759
 dst_confirm_neigh include/net/dst.h:420 [inline]
 udp_sendmsg+0x1105/0x2f70 net/ipv4/udp.c:1102
 udpv6_sendmsg+0x757/0x3400 net/ipv6/udp.c:1156
 inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:763
 sock_sendmsg_nosec net/socket.c:629 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:639
 SYSC_sendto+0x361/0x5c0 net/socket.c:1748
 SyS_sendto+0x40/0x50 net/socket.c:1716
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x453e69
RSP: 002b:00007f1074bccc68 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007f1074bcd6d4 RCX: 0000000000453e69
RDX: 0000000000000000 RSI: 00000000200003c0 RDI: 0000000000000013
RBP: 000000000072bf58 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000007ffc R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000004ca R14: 00000000006f7390 R15: 0000000000000001