INFO: rcu detected stall in group_pin

RDX: 0000000000000000 RSI: 0000000020000000 RDI: 0000000000000013
RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000014
R13: 00000000004c0dcb R14: 00000000004d1410 R15: 0000000000000001
IPVS: length: 4096 != 24
rcu: INFO: rcu_sched self-detected stall on CPU
rcu: 	1-....: (104999 ticks this GP) idle=b26/1/0x4000000000000002 softirq=44555/44555 fqs=26032 
rcu: 	 (t=105010 jiffies g=93449 q=1998)
NMI backtrace for cpu 1
CPU: 1 PID: 4377 Comm: syz-executor7 Not tainted 4.18.0-rc5-next-20180717+ #9
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+0x1c9/0x2b4 lib/dump_stack.c:113
 nmi_cpu_backtrace.cold.3+0x48/0x88 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x151/0x192 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+0x2fb/0x59c 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+0xd93/0x1660 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+0x3eb/0x10c0 kernel/time/hrtimer.c:1460
 hrtimer_interrupt+0x2f3/0x750 kernel/time/hrtimer.c:1518
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1025 [inline]
 smp_apic_timer_interrupt+0x165/0x730 arch/x86/kernel/apic/apic.c:1050
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:867
 </IRQ>
RIP: 0010:get_current arch/x86/include/asm/current.h:15 [inline]
RIP: 0010:write_comp_data+0xa/0x70 kernel/kcov.c:121
Code: e8 2b 7b 3e 00 e9 ad fc ff ff 4c 89 ef e8 7e 7a 3e 00 e9 76 fc ff ff e8 44 a3 ca ff 90 90 90 90 55 65 4c 8b 04 25 40 ee 01 00 <65> 8b 05 af 47 85 7e 48 89 e5 a9 00 01 1f 00 75 51 41 8b 80 98 12 
RSP: 0018:ffff8801a1a879b0 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: 1ffff10034350f53 RBX: ffffed0034350f40 RCX: ffffffff81d60da6
RDX: ffff8801c0004d80 RSI: 0000000000000000 RDI: 0000000000000007
RBP: ffff8801a1a879c0 R08: ffff8801a1a3e0c0 R09: 0000000000000000
R10: 0000000000000000 R11: dffffc0000000000 R12: dffffc0000000000
R13: ffff8801a1a87a98 R14: ffff8801c0004d80 R15: ffff8801a1a87a40
 group_pin_kill+0xc6/0x290 fs/fs_pin.c:97
 namespace_unlock+0x1c7/0x210 fs/namespace.c:1296
 do_umount fs/namespace.c:1490 [inline]
 ksys_umount+0x849/0x12f0 fs/namespace.c:1585
 __do_sys_umount fs/namespace.c:1596 [inline]
 __se_sys_umount fs/namespace.c:1594 [inline]
 __x64_sys_umount+0x54/0x80 fs/namespace.c:1594
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4584c7
Code: 44 00 00 b8 08 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 fd 8f fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 b8 a6 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 dd 8f fb ff c3 66 2e 0f 1f 84 00 00 00 00 
RSP: 002b:00007ffd3e19e358 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: ffffffffffffffda RBX: 0000000000031088 RCX: 00000000004584c7
RDX: 000000000000000c RSI: 0000000000000002 RDI: 00007ffd3e1a0100
RBP: 00007ffd3e1a0100 R08: 0000000000000001 R09: 0000000002a01940
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000000b
R13: 0000000000000000 R14: 00007ffd3e19fad0 R15: 0000000000702140
rcu: INFO: rcu_sched detected expedited stalls on CPUs/tasks: { 1-... } 105665 jiffies s: 2301 root: 0x2/.
rcu: blocking rcu_node structures:
Task dump for CPU 1:
syz-executor7   R  running task    21232  4377      1 0x8000000c
Call Trace:
 context_switch kernel/sched/core.c:2824 [inline]
 __schedule+0x884/0x1ea0 kernel/sched/core.c:3469
 schedule+0xfb/0x450 kernel/sched/core.c:3513
rcu: INFO: rcu_bh self-detected stall on CPU
rcu: 	1-....: (114339 ticks this GP) idle=b26/1/0x4000000000000002 softirq=40262/44555 fqs=26006 
rcu: 	 (t=105016 jiffies g=-971 q=1)
NMI backtrace for cpu 1
CPU: 1 PID: 4377 Comm: syz-executor7 Not tainted 4.18.0-rc5-next-20180717+ #9
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+0x1c9/0x2b4 lib/dump_stack.c:113
 nmi_cpu_backtrace.cold.3+0x48/0x88 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x151/0x192 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+0x2fb/0x59c 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+0xd93/0x1660 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+0x3eb/0x10c0 kernel/time/hrtimer.c:1460
 hrtimer_interrupt+0x2f3/0x750 kernel/time/hrtimer.c:1518
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1025 [inline]
 smp_apic_timer_interrupt+0x165/0x730 arch/x86/kernel/apic/apic.c:1050
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:867
 </IRQ>
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:783 [inline]
RIP: 0010:lock_acquire+0x25f/0x540 kernel/locking/lockdep.c:3927
Code: 00 00 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 6a 02 00 00 48 83 3d 68 40 92 07 00 0f 84 d4 01 00 00 48 8b bd 20 ff ff ff 57 9d <0f> 1f 44 00 00 48 b8 00 00 00 00 00 fc ff df 48 01 c3 48 c7 03 00 
RSP: 0018:ffff8801a1a878c8 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
RAX: dffffc0000000000 RBX: 1ffff10034350f1e RCX: 0000000000000000
RDX: 1ffffffff11e364d RSI: 0000000000000000 RDI: 0000000000000282
RBP: ffff8801a1a879b8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: dffffc0000000000 R12: ffff8801a1a3e0c0
R13: 0000000000000002 R14: 0000000000000000 R15: 0000000000000000
 rcu_lock_acquire include/linux/rcupdate.h:244 [inline]
 rcu_read_lock include/linux/rcupdate.h:629 [inline]
 group_pin_kill+0x10e/0x290 fs/fs_pin.c:95
 namespace_unlock+0x1c7/0x210 fs/namespace.c:1296
 do_umount fs/namespace.c:1490 [inline]
 ksys_umount+0x849/0x12f0 fs/namespace.c:1585
 __do_sys_umount fs/namespace.c:1596 [inline]
 __se_sys_umount fs/namespace.c:1594 [inline]
 __x64_sys_umount+0x54/0x80 fs/namespace.c:1594
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4584c7
Code: 44 00 00 b8 08 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 fd 8f fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 b8 a6 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 dd 8f fb ff c3 66 2e 0f 1f 84 00 00 00 00 
RSP: 002b:00007ffd3e19e358 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: ffffffffffffffda RBX: 0000000000031088 RCX: 00000000004584c7
RDX: 000000000000000c RSI: 0000000000000002 RDI: 00007ffd3e1a0100
RBP: 00007ffd3e1a0100 R08: 0000000000000001 R09: 0000000002a01940
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000000b
R13: 0000000000000000 R14: 00007ffd3e19fad0 R15: 0000000000702140