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Buffer I/O error on dev loop0, logical block 0, lost async page write
audit: type=1326 audit(1526460972.069:5): auid=4294967295 uid=0 gid=0 ses=4294967295 pid=9880 comm="syz-executor7" exe="/root/syz-executor7" sig=9 arch=c000003e syscall=202 compat=0 ip=0x455a09 code=0x0
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BUG: KMSAN: uninit-value in fprop_new_period+0x101/0x3f0 lib/flex_proportions.c:74
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.17.0-rc3+ #94
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:1084
 __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:683
 fprop_new_period+0x101/0x3f0 lib/flex_proportions.c:74
 writeout_period+0xd4/0x290 mm/page-writeback.c:634
 call_timer_fn+0x26a/0x5a0 kernel/time/timer.c:1326
 expire_timers kernel/time/timer.c:1363 [inline]
 __run_timers+0xda7/0x11c0 kernel/time/timer.c:1666
 run_timer_softirq+0x5f/0x70 kernel/time/timer.c:1694
 __do_softirq+0x56d/0x93d kernel/softirq.c:285
 invoke_softirq kernel/softirq.c:365 [inline]
 irq_exit+0x202/0x240 kernel/softirq.c:405
 exiting_irq+0xe/0x10 arch/x86/include/asm/apic.h:525
 smp_apic_timer_interrupt+0x64/0x90 arch/x86/kernel/apic/apic.c:1055
 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:ffffffff8ac0fd88 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: ffff8801fd431cf8 RBX: 0000000000000000 RCX: ffff880000000000
RDX: ffff8801fd031cf8 RSI: aaaaaaaaaaaab000 RDI: ffffea0000000000
RBP: ffffffff8ac0fdc0 R08: 0000000001080020 R09: 0000000000000002
R10: 00000000003fffc0 R11: 0000000000000000 R12: ffffffff8ac372c0
R13: ffffffff8ac37b98 R14: ffffffff8ac0fe24 R15: ffffffff8ac37b98
 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
 rest_init+0x1c1/0x1f0 init/main.c:442
 start_kernel+0x10fa/0x1110 init/main.c:739
 x86_64_start_reservations arch/x86/kernel/head64.c:454 [inline]
 x86_64_start_kernel+0x2fa/0x310 arch/x86/kernel/head64.c:435
 secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:242

Uninit was stored to memory at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:279 [inline]
 kmsan_save_stack mm/kmsan/kmsan.c:294 [inline]
 kmsan_internal_chain_origin+0x12b/0x210 mm/kmsan/kmsan.c:685
 __msan_chain_origin+0x69/0xc0 mm/kmsan/kmsan_instr.c:528
 percpu_counter_add_batch+0x306/0x380 lib/percpu_counter.c:92
 percpu_counter_add include/linux/percpu_counter.h:55 [inline]
 fprop_new_period+0x240/0x3f0 lib/flex_proportions.c:82
 writeout_period+0xd4/0x290 mm/page-writeback.c:634
 call_timer_fn+0x26a/0x5a0 kernel/time/timer.c:1326
 expire_timers kernel/time/timer.c:1363 [inline]
 __run_timers+0xda7/0x11c0 kernel/time/timer.c:1666
 run_timer_softirq+0x5f/0x70 kernel/time/timer.c:1694
 __do_softirq+0x56d/0x93d kernel/softirq.c:285
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
 __percpu_counter_sum+0x4c/0x2f0 lib/percpu_counter.c:112
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