Buffer I/O error on dev loop4, logical block 0, async page read
INFO: rcu_sched self-detected stall on CPU
	0-....: (124999 ticks this GP) idle=45a/1/4611686018427387906 softirq=152197/152197 fqs=31225 
	 (t=125000 jiffies g=82747 c=82746 q=749)
NMI backtrace for cpu 0
CPU: 0 PID: 26105 Comm: syz-executor4 Not tainted 4.15.0-rc7-mm1+ #56
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:53
 nmi_cpu_backtrace+0x1d2/0x210 lib/nmi_backtrace.c:103
 nmi_trigger_cpumask_backtrace+0x122/0x180 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:156 [inline]
 rcu_dump_cpu_stacks+0x186/0x1de kernel/rcu/tree.c:1375
 print_cpu_stall kernel/rcu/tree.c:1524 [inline]
 check_cpu_stall.isra.61+0xbb8/0x15b0 kernel/rcu/tree.c:1592
 __rcu_pending kernel/rcu/tree.c:3361 [inline]
 rcu_pending kernel/rcu/tree.c:3423 [inline]
 rcu_check_callbacks+0x238/0xd20 kernel/rcu/tree.c:2763
 update_process_times+0x30/0x60 kernel/time/timer.c:1628
 tick_sched_handle+0x85/0x160 kernel/time/tick-sched.c:162
 tick_sched_timer+0x42/0x120 kernel/time/tick-sched.c:1194
 __run_hrtimer kernel/time/hrtimer.c:1210 [inline]
 __hrtimer_run_queues+0x358/0xe20 kernel/time/hrtimer.c:1274
 hrtimer_interrupt+0x1c2/0x5e0 kernel/time/hrtimer.c:1308
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1025 [inline]
 smp_apic_timer_interrupt+0x14a/0x700 arch/x86/kernel/apic/apic.c:1050
 apic_timer_interrupt+0xa9/0xb0 arch/x86/entry/entry_64.S:926
 </IRQ>
RIP: 0010:check_kcov_mode kernel/kcov.c:67 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x1a/0x50 kernel/kcov.c:101
RSP: 0018:ffff8801a9a7fa90 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff11
RAX: ffff8801bd10c0c0 RBX: dffffc0000000000 RCX: ffffffff8399a47f
RDX: 0000000000000000 RSI: ffffc90002103000 RDI: ffff8801bd621bf8
RBP: ffff8801a9a7fa90 R08: 0000000000000000 R09: 1ffff1003534ff05
R10: ffff8801a9a7f7f0 R11: 0000000000000001 R12: ffff8801cea9e3d8
R13: ffff8801c27d84c0 R14: ffff88019f7ab340 R15: ffff8801c27d8610
 is_loop_device drivers/block/loop.c:691 [inline]
 loop_set_fd drivers/block/loop.c:879 [inline]
 lo_ioctl+0x561/0x1b70 drivers/block/loop.c:1358
 __blkdev_driver_ioctl block/ioctl.c:303 [inline]
 blkdev_ioctl+0x1759/0x1e00 block/ioctl.c:601
 block_ioctl+0xde/0x120 fs/block_dev.c:1859
 vfs_ioctl fs/ioctl.c:46 [inline]
 do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
 entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x452e39
RSP: 002b:00007fe7e20d9c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452e39
RDX: 0000000000000013 RSI: 0000000000004c00 RDI: 0000000000000015
RBP: 00000000000000ed R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006ef6d8
R13: 00000000ffffffff R14: 00007fe7e20da6d4 R15: 0000000000000000