rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-....: (10499 ticks this GP) idle=0da/1/0x4000000000000000 softirq=8294/8294 fqs=5231 
	(t=10500 jiffies g=9385 q=442)
NMI backtrace for cpu 1
CPU: 1 PID: 7079 Comm: syz-executor.0 Not tainted 5.8.0-rc6-next-20200724-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+0x18f/0x20d lib/dump_stack.c:118
 nmi_cpu_backtrace.cold+0x44/0xd7 lib/nmi_backtrace.c:105
 nmi_trigger_cpumask_backtrace+0x1b3/0x223 lib/nmi_backtrace.c:62
 trigger_single_cpu_backtrace include/linux/nmi.h:165 [inline]
 rcu_dump_cpu_stacks+0x194/0x1cf kernel/rcu/tree_stall.h:318
 print_cpu_stall kernel/rcu/tree_stall.h:551 [inline]
 check_cpu_stall kernel/rcu/tree_stall.h:625 [inline]
 rcu_pending kernel/rcu/tree.c:3626 [inline]
 rcu_sched_clock_irq.cold+0x5b3/0xcbd kernel/rcu/tree.c:2509
 update_process_times+0x25/0x60 kernel/time/timer.c:1737
 tick_sched_handle+0x9b/0x180 kernel/time/tick-sched.c:176
 tick_sched_timer+0x108/0x290 kernel/time/tick-sched.c:1328
 __run_hrtimer kernel/time/hrtimer.c:1520 [inline]
 __hrtimer_run_queues+0x1d5/0xfc0 kernel/time/hrtimer.c:1584
 hrtimer_interrupt+0x32a/0x930 kernel/time/hrtimer.c:1646
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1079 [inline]
 __sysvec_apic_timer_interrupt+0x142/0x5e0 arch/x86/kernel/apic/apic.c:1096
 asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:706
 </IRQ>
 __run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline]
 run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline]
 sysvec_apic_timer_interrupt+0xb2/0xf0 arch/x86/kernel/apic/apic.c:1090
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:590
RIP: 0010:iov_iter_copy_from_user_atomic+0x582/0xbe0 lib/iov_iter.c:1001
Code: d2 74 09 80 fa 03 0f 8e 93 05 00 00 8b 68 08 48 89 44 24 38 ba 00 10 00 00 8b 44 24 14 8b 4c 24 20 44 29 fd 81 e1 ff 0f 00 00 <39> c5 0f 47 e8 29 ca 89 4c 24 30 39 d5 0f 47 ea 31 ff 89 ee e8 a5
RSP: 0018:ffffc900061e7750 EFLAGS: 00000246
RAX: 00000000000000d2 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000001000 RSI: ffffffff8398da05 RDI: ffff88809f013408
RBP: 0000000000000000 R08: 0000000000000000 R09: ffff888087b5b57f
R10: 0000000000000000 R11: 0000000000000000 R12: ffff88809f013400
R13: 0000000000000000 R14: dffffc0000000000 R15: 0000000000000000
 generic_perform_write+0x277/0x4f0 mm/filemap.c:3368
 ext4_buffered_write_iter+0x235/0x4a0 fs/ext4/file.c:270
 ext4_file_write_iter+0x1f3/0x13d0 fs/ext4/file.c:655
 call_write_iter include/linux/fs.h:1883 [inline]
 do_iter_readv_writev+0x567/0x780 fs/read_write.c:730
 do_iter_write+0x188/0x630 fs/read_write.c:1035
 vfs_iter_write+0x70/0xa0 fs/read_write.c:1076
 iter_file_splice_write+0x721/0xbe0 fs/splice.c:667
 do_splice_from fs/splice.c:736 [inline]
 do_splice+0xbb8/0x17a0 fs/splice.c:1043
 __do_sys_splice fs/splice.c:1318 [inline]
 __se_sys_splice fs/splice.c:1300 [inline]
 __x64_sys_splice+0x198/0x250 fs/splice.c:1300
 do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45c369
Code: Bad RIP value.
RSP: 002b:00007fb2d739ec78 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
RAX: ffffffffffffffda RBX: 0000000000032240 RCX: 000000000045c369
RDX: 0000000000000003 RSI: 0000000000000000 RDI: 0000000000000006
RBP: 000000000078bf58 R08: 000000000000ffe0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000078bf0c
R13: 00007ffe3367ac4f R14: 00007fb2d739f9c0 R15: 000000000078bf0c