syzbot

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	0-...!: (2 GPs behind) idle=25e/1/0x4000000000000002 softirq=31087/31088 fqs=0 
rcu: 	 (t=10501 jiffies g=36173 q=141)
rcu: rcu_preempt kthread starved for 10502 jiffies! g36173 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
rcu: RCU grace-period kthread stack dump:
rcu_preempt     R  running task    22736    10      2 0x80000000
Call Trace:
 context_switch kernel/sched/core.c:2825 [inline]
 __schedule+0x86c/0x1ed0 kernel/sched/core.c:3473
 schedule+0xfe/0x460 kernel/sched/core.c:3517
 schedule_timeout+0x140/0x260 kernel/time/timer.c:1804
 rcu_gp_kthread+0x9d9/0x2310 kernel/rcu/tree.c:2194
 kthread+0x35a/0x420 kernel/kthread.c:246
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:413
NMI backtrace for cpu 0
CPU: 0 PID: 20739 Comm: syz-executor0 Not tainted 4.19.0-rc2+ #6
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1c4/0x2b4 lib/dump_stack.c:113
 nmi_cpu_backtrace.cold.3+0x63/0xa2 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x1b3/0x1ed 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:162 [inline]
 rcu_dump_cpu_stacks+0x175/0x1c2 kernel/rcu/tree.c:1340
 print_cpu_stall.cold.78+0x2d3/0x524 kernel/rcu/tree.c:1478
 check_cpu_stall kernel/rcu/tree.c:1550 [inline]
 __rcu_pending kernel/rcu/tree.c:3276 [inline]
 rcu_pending kernel/rcu/tree.c:3319 [inline]
 rcu_check_callbacks+0xfd9/0x1990 kernel/rcu/tree.c:2665
 update_process_times+0x2d/0x70 kernel/time/timer.c:1636
 tick_sched_handle+0x9f/0x180 kernel/time/tick-sched.c:164
 tick_sched_timer+0x45/0x130 kernel/time/tick-sched.c:1274
 __run_hrtimer kernel/time/hrtimer.c:1398 [inline]
 __hrtimer_run_queues+0x41c/0x10d0 kernel/time/hrtimer.c:1460
 hrtimer_interrupt+0x313/0x780 kernel/time/hrtimer.c:1518
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1029 [inline]
 smp_apic_timer_interrupt+0x1a1/0x760 arch/x86/kernel/apic/apic.c:1054
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:864
 </IRQ>
RIP: 0010:__sanitizer_cov_trace_const_cmp4+0x16/0x20 kernel/kcov.c:188
Code: 48 89 e5 48 8b 4d 08 e8 88 fe ff ff 5d c3 66 0f 1f 44 00 00 55 89 f2 89 fe bf 05 00 00 00 48 89 e5 48 8b 4d 08 e8 6a fe ff ff <5d> c3 0f 1f 84 00 00 00 00 00 55 48 89 f2 48 89 fe bf 07 00 00 00
RSP: 0018:ffff880181e26ad8 EFLAGS: 00000297 ORIG_RAX: ffffffffffffff13
RAX: 0000000000000002 RBX: ffffc90001955000 RCX: ffffffff8108c6b9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: ffff880181e26ad8 R08: ffff880187890380 R09: ffffed003045de21
R10: ffffed003045de21 R11: ffff8801822ef10b R12: dffffc0000000000
R13: 0000000000000000 R14: ffff8801822e3d00 R15: ffff880181e26c30
 __kvm_memslots include/linux/kvm_host.h:581 [inline]
 kvm_vcpu_memslots include/linux/kvm_host.h:595 [inline]
 kvm_vcpu_gfn_to_memslot+0x5c9/0x7f0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:1229
 mapping_level+0x64/0x4c0 arch/x86/kvm/mmu.c:1165
 tdp_page_fault+0x27f/0xbe0 arch/x86/kvm/mmu.c:4049
 kvm_mmu_page_fault+0x226/0x1b30 arch/x86/kvm/mmu.c:5233
 handle_ept_violation+0x29e/0x6a0 arch/x86/kvm/vmx.c:7679
 vmx_handle_exit+0x2f7/0x17e0 arch/x86/kvm/vmx.c:10115
 vcpu_enter_guest+0x14a9/0x62e0 arch/x86/kvm/x86.c:7648
 vcpu_run arch/x86/kvm/x86.c:7711 [inline]
 kvm_arch_vcpu_ioctl_run+0x375/0x16e0 arch/x86/kvm/x86.c:7888
 kvm_vcpu_ioctl+0x72b/0x1150 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2590
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:501 [inline]
 do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685
 ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702
 __do_sys_ioctl fs/ioctl.c:709 [inline]
 __se_sys_ioctl fs/ioctl.c:707 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457099
Code: fd b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 cb b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f85e43bec78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f85e43bf6d4 RCX: 0000000000457099
RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000006
RBP: 00000000009300a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004cf730 R14: 00000000004c59b9 R15: 0000000000000000
f2fs_msg: 46 callbacks suppressed
F2FS-fs (loop6): Unable to read 1th superblock
print_req_error: 47 callbacks suppressed
print_req_error: I/O error, dev loop6, sector 8
F2FS-fs (loop6): Unable to read 2th superblock
print_req_error: I/O error, dev loop6, sector 0
F2FS-fs (loop6): Unable to read 1th superblock
print_req_error: I/O error, dev loop6, sector 8
F2FS-fs (loop6): Unable to read 2th superblock