syzbot

RAX: ffffffffffffffda RBX: 00007f3ca2a716d4 RCX: 0000000000457089
RDX: 0000000020000080 RSI: 0000000020000040 RDI: 0000000020000200
RBP: 00000000009300a0 R08: 00000000200000c0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000003
R13: 00000000004d22f8 R14: 00000000004c7a30 R15: 0000000000000062
INFO: rcu_sched self-detected stall on CPU
	1-....: (1 GPs behind) idle=53e/1/4611686018427387906 softirq=115968/115969 fqs=24950 
	 (t=100000 jiffies g=40025 c=40024 q=1217)
NMI backtrace for cpu 1
CPU: 1 PID: 1791 Comm: syz-executor3 Not tainted 4.18.0-rc8+ #32
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+0xae/0xf0 lib/dump_stack.c:113
 nmi_cpu_backtrace lib/nmi_backtrace.c:103 [inline]
 nmi_trigger_cpumask_backtrace+0xdd/0x1e0 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:156 [inline]
 rcu_dump_cpu_stacks+0xd9/0xf0 kernel/rcu/tree.c:1336
 print_cpu_stall kernel/rcu/tree.c:1485 [inline]
 check_cpu_stall kernel/rcu/tree.c:1553 [inline]
 __rcu_pending kernel/rcu/tree.c:3244 [inline]
 rcu_pending kernel/rcu/tree.c:3291 [inline]
 rcu_check_callbacks+0x468/0x800 kernel/rcu/tree.c:2646
 update_process_times+0x77/0xc0 kernel/time/timer.c:1636
 tick_sched_handle kernel/time/tick-sched.c:164 [inline]
 tick_sched_timer+0xe1/0x140 kernel/time/tick-sched.c:1274
 __run_hrtimer kernel/time/hrtimer.c:1398 [inline]
 __hrtimer_run_queues+0x270/0x480 kernel/time/hrtimer.c:1460
 hrtimer_interrupt+0x140/0x4f0 kernel/time/hrtimer.c:1518
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1028 [inline]
 smp_apic_timer_interrupt+0xb5/0x1b0 arch/x86/kernel/apic/apic.c:1056
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:868
 </IRQ>
RIP: 0010:iov_iter_copy_from_user_atomic+0x1e1/0x440 lib/iov_iter.c:922
Code: 84 68 01 00 00 49 8b 54 24 18 c7 45 d0 00 00 00 00 41 89 de eb 09 e8 4e 1b 76 ff 48 8b 55 b8 8b 45 d0 48 c1 e0 04 8b 5c 02 08 <44> 29 eb 41 39 de 41 0f 42 de 85 db 0f 84 9a 00 00 00 8b 4c 02 0c 
RSP: 0018:ffff8801dacd3a20 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000040000
RDX: ffff8801e7f4f000 RSI: 000000000003ffff RDI: 0000000000040000
RBP: ffff8801dacd3a70 R08: ffff880216588e70 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: ffff8801dacd3ca8
R13: 0000000000000000 R14: 0000000000000001 R15: ffff8801cc62df6d
 generic_perform_write+0x14c/0x260 mm/filemap.c:3147
 __generic_file_write_iter+0xe2/0x1f0 mm/filemap.c:3264
 generic_file_write_iter+0x1a2/0x270 mm/filemap.c:3292
 do_iter_readv_writev+0x1c5/0x210 include/linux/fs.h:1787
 do_iter_write+0x9f/0x270 fs/read_write.c:959
 vfs_iter_write+0x3d/0x60 fs/read_write.c:972
 iter_file_splice_write+0x23f/0x4d0 fs/splice.c:750
 do_splice_from fs/splice.c:852 [inline]
 direct_splice_actor+0x42/0x50 fs/splice.c:1019
 splice_direct_to_actor+0x174/0x350 fs/splice.c:974
 do_splice_direct+0x87/0xe0 fs/splice.c:1062
 do_sendfile+0x424/0x680 fs/read_write.c:1440
 __do_sys_sendfile64 fs/read_write.c:1495 [inline]
 __se_sys_sendfile64 fs/read_write.c:1487 [inline]
 __x64_sys_sendfile64+0x59/0xb0 fs/read_write.c:1487
 do_syscall_64+0x61/0x90 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x457089
Code: fd b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 cb b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 
RSP: 002b:00007fa2802bbc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007fa2802bc6d4 RCX: 0000000000457089
RDX: 0000000020000240 RSI: 0000000000000003 RDI: 0000000000000003
RBP: 00000000009300a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000010000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004d3840 R14: 00000000004c85ae R15: 0000000000000000
INFO: rcu_sched detected expedited stalls on CPUs/tasks: { 1-... } 102275 jiffies s: 19933 root: 0x2/.
blocking rcu_node structures:
Task dump for CPU 1:
syz-executor3   R  running task    12936  1791   4111 0x8000000c
Call Trace:
 context_switch kernel/sched/core.c:2860 [inline]
 __schedule+0x632/0x870 kernel/sched/core.c:3507
 preempt_schedule_common kernel/sched/core.c:3631 [inline]
 _cond_resched+0x2f/0x60 kernel/sched/core.c:4999
 find_lock_entry+0x198/0x1c0 mm/filemap.c:1499
 shmem_getpage_gfp+0x12c8/0x1370 mm/shmem.c:1667