syzbot

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	0-...!: (1 GPs behind) idle=78e/1/0x4000000000000002 softirq=11701/11704 fqs=145 
	(t=10501 jiffies g=7613 q=355)
rcu: rcu_preempt kthread starved for 10212 jiffies! g7613 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
rcu: RCU grace-period kthread stack dump:
rcu_preempt     R  running task    28984    10      2 0x80004000
Call Trace:
 context_switch kernel/sched/core.c:3385 [inline]
 __schedule+0x9a0/0xcc0 kernel/sched/core.c:4081
 schedule+0x181/0x210 kernel/sched/core.c:4155
 schedule_timeout+0x14f/0x240 kernel/time/timer.c:1895
 rcu_gp_fqs_loop kernel/rcu/tree.c:1661 [inline]
 rcu_gp_kthread+0xed8/0x1770 kernel/rcu/tree.c:1821
 kthread+0x332/0x350 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
NMI backtrace for cpu 0
CPU: 0 PID: 8634 Comm: udevd Not tainted 5.5.0-rc5-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:77 [inline]
 dump_stack+0x1fb/0x318 lib/dump_stack.c:118
 nmi_cpu_backtrace+0xaf/0x1a0 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x174/0x290 lib/nmi_backtrace.c:62
 arch_trigger_cpumask_backtrace+0x10/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline]
 rcu_dump_cpu_stacks+0x15a/0x220 kernel/rcu/tree_stall.h:254
 print_cpu_stall kernel/rcu/tree_stall.h:455 [inline]
 check_cpu_stall kernel/rcu/tree_stall.h:529 [inline]
 rcu_pending kernel/rcu/tree.c:2827 [inline]
 rcu_sched_clock_irq+0xe25/0x1ad0 kernel/rcu/tree.c:2271
 update_process_times+0x12d/0x180 kernel/time/timer.c:1726
 tick_sched_handle kernel/time/tick-sched.c:167 [inline]
 tick_sched_timer+0x263/0x420 kernel/time/tick-sched.c:1310
 __run_hrtimer kernel/time/hrtimer.c:1517 [inline]
 __hrtimer_run_queues+0x403/0x840 kernel/time/hrtimer.c:1579
 hrtimer_interrupt+0x38c/0xda0 kernel/time/hrtimer.c:1641
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1110 [inline]
 smp_apic_timer_interrupt+0x109/0x280 arch/x86/kernel/apic/apic.c:1135
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829
 </IRQ>
RIP: 0010:__sanitizer_cov_trace_pc+0x0/0x50 kernel/kcov.c:183
Code: 66 2e 0f 1f 84 00 00 00 00 00 55 48 89 e5 53 48 89 fb e8 13 00 00 00 48 8b 3d f4 f4 ed 07 48 89 de e8 84 f4 3b 00 5b 5d c3 cc <48> 8b 04 24 65 48 8b 0c 25 c0 1d 02 00 65 8b 15 38 5f 8b 7e f7 c2
RSP: 0018:ffffc90001d178c0 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: 1ffff11011dfe9b1 RBX: ffffea000254f2c0 RCX: ffff888093a7a300
RDX: 0000000000000000 RSI: 00000000fffffffc RDI: ffffea000254f2c0
RBP: ffffc90001d17900 R08: 000000000003a728 R09: ffffed1014504b09
R10: ffffed1014504b09 R11: 0000000000000000 R12: ffff88808eff4e20
R13: dffffc0000000000 R14: 1ffff11011dfe9c4 R15: ffff8880a2825838
 release_task_stack kernel/fork.c:440 [inline]
 put_task_stack+0xa3/0x130 kernel/fork.c:451
 finish_task_switch+0x3f1/0x550 kernel/sched/core.c:3256
 context_switch kernel/sched/core.c:3388 [inline]
 __schedule+0x9a8/0xcc0 kernel/sched/core.c:4081
 preempt_schedule_irq+0xc1/0x140 kernel/sched/core.c:4338
 retint_kernel+0x1b/0x2b
RIP: 0010:rb_prev+0x60/0xe0 lib/rbtree.c:535
Code: e9 94 00 00 00 49 8d 5e 10 48 89 d8 48 c1 e8 03 42 80 3c 20 00 74 08 48 89 df e8 6b 78 b7 f9 48 8b 03 48 85 c0 74 33 0f 1f 00 <49> 89 c7 48 8d 58 08 48 89 d8 48 c1 e8 03 42 80 3c 20 00 74 08 48
RSP: 0018:ffffc90001d17b10 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff02
RAX: ffff88808e026758 RBX: ffff8880a1d01380 RCX: ffff888093a7a300
RDX: 0000000000000000 RSI: ffff888093a7a300 RDI: ffff8880984d0ed0
RBP: ffffc90001d17b30 R08: dffffc0000000000 R09: ffffed10130b8130
R10: ffffed10130b8130 R11: 0000000000000000 R12: dffffc0000000000
R13: 1ffff110130b812e R14: ffff8880984d0ed0 R15: ffff8880a1d01378
 browse_rb mm/mmap.c:367 [inline]
 validate_mm+0x814/0x9b0 mm/mmap.c:420
 vma_link+0x264/0x290 mm/mmap.c:660
 mmap_region+0x12e1/0x1cb0 mm/mmap.c:1801
 do_mmap+0xabb/0x1120 mm/mmap.c:1549
 do_mmap_pgoff include/linux/mm.h:2338 [inline]
 vm_mmap_pgoff+0x13d/0x1d0 mm/util.c:506
 ksys_mmap_pgoff+0x104/0x560 mm/mmap.c:1601
 __do_sys_mmap arch/x86/kernel/sys_x86_64.c:100 [inline]
 __se_sys_mmap arch/x86/kernel/sys_x86_64.c:91 [inline]
 __x64_sys_mmap+0x103/0x120 arch/x86/kernel/sys_x86_64.c:91
 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7fe926f64d0a
Code: b8 ff ff ff ff e9 fa fe ff ff 48 63 fb b8 03 00 00 00 0f 05 b8 ff ff ff ff e9 e6 fe ff ff 90 90 49 89 ca b8 09 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d fe c0 2a 00 31 d2 48 29 c2 64
RSP: 002b:00007ffc316fcbe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00000000024ad160 RCX: 00007fe926f64d0a
RDX: 0000000000000003 RSI: 0000000000001000 RDI: 0000000000000000
RBP: 0000000000001000 R08: 00000000ffffffff R09: 0000000000000000
R10: 0000000000000022 R11: 0000000000000246 R12: 0000000000420724
R13: 0000000000000002 R14: 0000000000420724 R15: 0000000000420724