syzbot

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BUG: KMSAN: uninit-value in tick_irq_enter+0x323/0x3b0 kernel/time/tick-sched.c:1250
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.17.0-rc3+ #88
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+0x185/0x1d0 lib/dump_stack.c:113
 kmsan_report+0x142/0x240 mm/kmsan/kmsan.c:1067
 __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:683
 tick_irq_enter+0x323/0x3b0 kernel/time/tick-sched.c:1250
 irq_enter+0x5a/0xa0 kernel/softirq.c:346
 entering_irq arch/x86/include/asm/apic.h:508 [inline]
 entering_ack_irq+0x16/0x70 arch/x86/include/asm/apic.h:513
 smp_apic_timer_interrupt+0x50/0x90 arch/x86/kernel/apic/apic.c:1051
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:863
 </IRQ>
RIP: 0010:native_safe_halt arch/x86/include/asm/irqflags.h:55 [inline]
RIP: 0010:arch_safe_halt arch/x86/include/asm/irqflags.h:97 [inline]
RIP: 0010:default_idle+0x1fb/0x3c0 arch/x86/kernel/process.c:354
RSP: 0018:ffff8801d8e5fdf0 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: ffff8801fd431d78 RBX: 0000000000000000 RCX: ffff880000000000
RDX: ffff8801fd031d78 RSI: aaaaaaaaaaaab000 RDI: ffffea0000000000
RBP: ffff8801d8e5fe28 R08: 0000000001080020 R09: 0000000000000002
R10: 0000000000000003 R11: 0000000000000000 R12: ffff8801d8da57c0
R13: ffff8801d8da6098 R14: ffff8801d8e5fe8c R15: ffff8801d8da6098
 arch_cpu_idle+0x20/0x30 arch/x86/kernel/process.c:345
 default_idle_call kernel/sched/idle.c:93 [inline]
 cpuidle_idle_call kernel/sched/idle.c:153 [inline]
 do_idle+0x458/0x850 kernel/sched/idle.c:262
 cpu_startup_entry+0x45/0x50 kernel/sched/idle.c:368
 start_secondary+0x39d/0x470 arch/x86/kernel/smpboot.c:269
 secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:242

Local variable description: ----flags.i.i.i.i@_raw_spin_lock_irqsave
Variable was created at:
 _raw_spin_lock_irqsave+0x45/0xf0 kernel/locking/spinlock.c:150
 rcu_cpu_starting kernel/rcu/tree.c:3803 [inline]
 rcu_init+0x15d7/0x1a60 kernel/rcu/tree.c:4195
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